Artykuły w czasopismach: „E3 LIGASE ACTIVITY”

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Pao, Kuan-Chuan, Nicola T. Wood, Axel Knebel, Karim Rafie, Mathew Stanley, Peter D. Mabbitt, Ramasubramanian Sundaramoorthy, Kay Hofmann, Daan M. F. van Aalten i Satpal Virdee. "Activity-based E3 ligase profiling uncovers an E3 ligase with esterification activity". Nature 556, nr 7701 (kwiecień 2018): 381–85. http://dx.doi.org/10.1038/s41586-018-0026-1.

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Marblestone, Jeffrey G., K. G. Suresh Kumar, Michael J. Eddins, Craig A. Leach, David E. Sterner, Michael R. Mattern i Benjamin Nicholson. "Novel Approach for Characterizing Ubiquitin E3 Ligase Function". Journal of Biomolecular Screening 15, nr 10 (23.09.2010): 1220–28. http://dx.doi.org/10.1177/1087057110380456.

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The ubiquitin-proteasome system is central to the regulation of numerous cellular events, and dysregulation may lead to disease pathogenesis. E3 ubiquitin ligases typically function in concert with E1 and E2 enzymes to recruit specific substrates, thereby coordinating their ubiquitylation and subsequent proteasomal degradation or cellular activity. E3 ligases have been implicated in a wide range of pathologies, and monitoring their activity in a rapid and cost-effective manner would be advantageous in drug discovery. The relative lack of high-throughput screening (HTS)–compliant E3 ligase assays has significantly hindered the discovery of E3 inhibitors. Herein, the authors describe a novel HTS-compliant E3 ligase assay platform that takes advantage of a ubiquitin binding domain’s inherent affinity for polyubiquitin chains, permitting the analysis of ubiquitin chain formation in an E3 ligase-dependent manner. This assay has been used successfully with members of both the RING and HECT families, demonstrating the platform’s broad utility for analyzing a wide range of E3 ligases. The utility of the assay platform is demonstrated by the identification of inhibitors of the E3 ligase CARP2. As the number of E3 ligases associated with various disease states increases, the ability to quantitate the activity of these enzymes in an expeditious manner becomes imperative in drug discovery.

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Li, Qianyan, Arshdeep Kaur, Kyoko Okada, Richard J. McKenney i JoAnne Engebrecht. "Differential requirement for BRCA1-BARD1 E3 ubiquitin ligase activity in DNA damage repair and meiosis in the Caenorhabditis elegans germ line". PLOS Genetics 19, nr 1 (30.01.2023): e1010457. http://dx.doi.org/10.1371/journal.pgen.1010457.

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The tumor suppressor BRCA1-BARD1 complex regulates many cellular processes; of critical importance to its tumor suppressor function is its role in genome integrity. Although RING E3 ubiquitin ligase activity is the only known enzymatic activity of the complex, the in vivo requirement for BRCA1-BARD1 E3 ubiquitin ligase activity has been controversial. Here we probe the role of BRCA1-BARD1 E3 ubiquitin ligase activity in vivo using C. elegans. Genetic, cell biological, and biochemical analyses of mutants defective for E3 ligase activity suggest there is both E3 ligase-dependent and independent functions of the complex in the context of DNA damage repair and meiosis. We show that E3 ligase activity is important for nuclear accumulation of the complex and specifically to concentrate at meiotic recombination sites but not at DNA damage sites in proliferating germ cells. While BRCA1 alone is capable of monoubiquitylation, BARD1 is required with BRCA1 to promote polyubiquitylation. We find that the requirement for E3 ligase activity and BARD1 in DNA damage signaling and repair can be partially alleviated by driving the nuclear accumulation and self-association of BRCA1. Our data suggest that in addition to E3 ligase activity, BRCA1 may serve a structural role for DNA damage signaling and repair while BARD1 plays an accessory role to enhance BRCA1 function.

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Kim, Jong Hum, Seok Keun Cho, Tae Rin Oh, Moon Young Ryu, Seong Wook Yang i Woo Taek Kim. "MPSR1 is a cytoplasmic PQC E3 ligase for eliminating emergent misfolded proteins in Arabidopsis thaliana". Proceedings of the National Academy of Sciences 114, nr 46 (30.10.2017): E10009—E10017. http://dx.doi.org/10.1073/pnas.1713574114.

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Ubiquitin E3 ligases are crucial for eliminating misfolded proteins before they form cytotoxic aggregates that threaten cell fitness and survival. However, it remains unclear how emerging misfolded proteins in the cytoplasm can be selectively recognized and eliminated by E3 ligases in plants. We found that Misfolded Protein Sensing RING E3 ligase 1 (MPSR1) is an indispensable E3 ligase required for plant survival after protein-damaging stress. Under no stress, MPSR1 is prone to rapid degradation by the 26S proteasome, concealing its protein quality control (PQC) E3 ligase activity. Upon proteotoxic stress, MPSR1 directly senses incipient misfolded proteins and tethers ubiquitins for subsequent degradation. Furthermore, MPSR1 sustains the structural integrity of the proteasome complex at the initial stage of proteotoxic stress. Here, we suggest that the MPSR1 pathway is a constitutive mechanism for proteostasis under protein-damaging stress, as a front-line surveillance system in the cytoplasm.

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Bustos, Francisco, Sunil Mathur, Carmen Espejo-Serrano, Rachel Toth, C. James Hastie, Satpal Virdee i Greg M. Findlay. "Activity-based probe profiling of RNF12 E3 ubiquitin ligase function in Tonne-Kalscheuer syndrome". Life Science Alliance 5, nr 11 (28.06.2022): e202101248. http://dx.doi.org/10.26508/lsa.202101248.

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Ubiquitylation enzymes are involved in all aspects of eukaryotic biology and are frequently disrupted in disease. One example is the E3 ubiquitin ligase RNF12/RLIM, which is mutated in the developmental disorder Tønne-Kalscheuer syndrome (TOKAS). RNF12 TOKAS variants largely disrupt catalytic E3 ubiquitin ligase activity, which presents a pressing need to develop approaches to assess the impact of variants on RNF12 activity in patients. Here, we use photocrosslinking activity-based probes (photoABPs) to monitor RNF12 RING E3 ubiquitin ligase activity in normal and pathogenic contexts. We demonstrate that photoABPs undergo UV-induced labelling of RNF12 that is consistent with its RING E3 ligase activity. Furthermore, photoABPs robustly report the impact of RNF12 TOKAS variants on E3 activity, including variants within the RING domain and distal non-RING regulatory elements. Finally, we show that this technology can be rapidly deployed in human pluripotent stem cells. In summary, photoABPs are versatile tools that can directly identify disruptions to RING E3 ubiquitin ligase activity in human disease, thereby providing new insight into pathogenic mechanisms.

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Chinnam, Meenalakshmi, Chao Xu, Rati Lama, Xiaojing Zhang, Carlos D. Cedeno, Yanqing Wang, Aimee B. Stablewski, David W. Goodrich i Xinjiang Wang. "MDM2 E3 ligase activity is essential for p53 regulation and cell cycle integrity". PLOS Genetics 18, nr 5 (19.05.2022): e1010171. http://dx.doi.org/10.1371/journal.pgen.1010171.

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MDM2 and MDM4 are key regulators of p53 and function as oncogenes when aberrantly expressed. MDM2 and MDM4 partner to suppress p53 transcriptional transactivation and polyubiquitinate p53 for degradation. The importance of MDM2 E3-ligase-mediated p53 regulation remains controversial. To resolve this, we generated mice with an Mdm2 L466A mutation that specifically compromises E2 interaction, abolishing MDM2 E3 ligase activity while preserving its ability to bind MDM4 and suppress p53 transactivation. Mdm2L466A/L466A mice exhibit p53-dependent embryonic lethality, demonstrating MDM2 E3 ligase activity is essential for p53 regulation in vivo. Unexpectedly, cells expressing Mdm2L466A manifest cell cycle G2-M transition defects and increased aneuploidy even in the absence of p53, suggesting MDM2 E3 ligase plays a p53-independent role in cell cycle regulation and genome integrity. Furthermore, cells bearing the E3-dead MDM2 mutant show aberrant cell cycle regulation in response to DNA damage. This study uncovers an uncharacterized role for MDM2’s E3 ligase activity in cell cycle beyond its essential role in regulating p53’s stability in vivo.

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Gong, Yao, i Yue Chen. "UbE3-APA: a bioinformatic strategy to elucidate ubiquitin E3 ligase activities in quantitative proteomics study". Bioinformatics 38, nr 8 (9.02.2022): 2211–18. http://dx.doi.org/10.1093/bioinformatics/btac069.

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Abstract Motivation Ubiquitination is widely involved in protein homeostasis and cell signaling. Ubiquitin E3 ligases are critical regulators of ubiquitination that recognize and recruit specific ubiquitination targets for the final rate-limiting step of ubiquitin transfer reactions. Understanding the ubiquitin E3 ligase activities will provide knowledge in the upstream regulator of the ubiquitination pathway and reveal potential mechanisms in biological processes and disease progression. Recent advances in mass spectrometry-based proteomics have enabled deep profiling of ubiquitylome in a quantitative manner. Yet, functional analysis of ubiquitylome dynamics and pathway activity remains challenging. Results Here, we developed a UbE3-APA, a computational algorithm and stand-alone python-based software for Ub E3 ligase Activity Profiling Analysis. Combining an integrated annotation database with statistical analysis, UbE3-APA identifies significantly activated or suppressed E3 ligases based on quantitative ubiquitylome proteomics datasets. Benchmarking the software with published quantitative ubiquitylome analysis confirms the genetic manipulation of SPOP enzyme activity through overexpression and mutation. Application of the algorithm in the re-analysis of a large cohort of ubiquitination proteomics study revealed the activation of PARKIN and the co-activation of other E3 ligases in mitochondria depolarization-induced mitophagy process. We further demonstrated the application of the algorithm in the DIA (data-independent acquisition)-based quantitative ubiquitylome analysis. Availability and implementation Source code and binaries are freely available for download at URL: https://github.com/Chenlab-UMN/Ub-E3-ligase-Activity-Profiling-Analysis, implemented in python and supported on Linux and MS Windows. Supplementary information Supplementary data are available at Bioinformatics online.

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Horn-Ghetko, Daniel, David T. Krist, J. Rajan Prabu, Kheewoong Baek, Monique P. C. Mulder, Maren Klügel, Daniel C. Scott, Huib Ovaa, Gary Kleiger i Brenda A. Schulman. "Ubiquitin ligation to F-box protein targets by SCF–RBR E3–E3 super-assembly". Nature 590, nr 7847 (3.02.2021): 671–76. http://dx.doi.org/10.1038/s41586-021-03197-9.

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AbstractE3 ligases are typically classified by hallmark domains such as RING and RBR, which are thought to specify unique catalytic mechanisms of ubiquitin transfer to recruited substrates1,2. However, rather than functioning individually, many neddylated cullin–RING E3 ligases (CRLs) and RBR-type E3 ligases in the ARIH family—which together account for nearly half of all ubiquitin ligases in humans—form E3–E3 super-assemblies3–7. Here, by studying CRLs in the SKP1–CUL1–F-box (SCF) family, we show how neddylated SCF ligases and ARIH1 (an RBR-type E3 ligase) co-evolved to ubiquitylate diverse substrates presented on various F-box proteins. We developed activity-based chemical probes that enabled cryo-electron microscopy visualization of steps in E3–E3 ubiquitylation, initiating with ubiquitin linked to the E2 enzyme UBE2L3, then transferred to the catalytic cysteine of ARIH1, and culminating in ubiquitin linkage to a substrate bound to the SCF E3 ligase. The E3–E3 mechanism places the ubiquitin-linked active site of ARIH1 adjacent to substrates bound to F-box proteins (for example, substrates with folded structures or limited length) that are incompatible with previously described conventional RING E3-only mechanisms. The versatile E3–E3 super-assembly may therefore underlie widespread ubiquitylation.

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Kelsall, Ian R., Jiazhen Zhang, Axel Knebel, J. Simon C. Arthur i Philip Cohen. "The E3 ligase HOIL-1 catalyses ester bond formation between ubiquitin and components of the Myddosome in mammalian cells". Proceedings of the National Academy of Sciences 116, nr 27 (17.06.2019): 13293–98. http://dx.doi.org/10.1073/pnas.1905873116.

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The linear ubiquitin assembly complex (LUBAC) comprises 3 components: HOIP, HOIL-1, and Sharpin, of which HOIP and HOIL-1 are both members of the RBR subfamily of E3 ubiquitin ligases. HOIP catalyses the formation of Met1-linked ubiquitin oligomers (also called linear ubiquitin), but the function of the E3 ligase activity of HOIL-1 is unknown. Here, we report that HOIL-1 is an atypical E3 ligase that forms oxyester bonds between the C terminus of ubiquitin and serine and threonine residues in its substrates. Exploiting the sensitivity of HOIL-1–generated oxyester bonds to cleavage by hydroxylamine, and macrophages from knock-in mice expressing the E3 ligase-inactive HOIL-1[C458S] mutant, we identify IRAK1, IRAK2, and MyD88 as physiological substrates of the HOIL-1 E3 ligase during Toll-like receptor signaling. HOIL-1 is a monoubiquitylating E3 ubiquitin ligase that initiates the de novo synthesis of polyubiquitin chains that are attached to these proteins in macrophages. HOIL-1 also catalyses its own monoubiquitylation in cells and most probably the monoubiquitylation of Sharpin, in which ubiquitin is also attached by an oxyester bond. Our study establishes that oxyester-linked ubiquitylation is used as an intracellular signaling mechanism.

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Li, Haoyan, Yanjia Fang, Chunyi Niu, Hengyi Cao, Ting Mi, Hong Zhu, Junying Yuan i Jidong Zhu. "Inhibition of cIAP1 as a strategy for targeting c-MYC–driven oncogenic activity". Proceedings of the National Academy of Sciences 115, nr 40 (4.09.2018): E9317—E9324. http://dx.doi.org/10.1073/pnas.1807711115.

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Protooncogenec-MYC, a master transcription factor, is a major driver of human tumorigenesis. Development of pharmacological agents for inhibiting c-MYC as an anticancer therapy has been a longstanding but elusive goal in the cancer field. E3 ubiquitin ligase cIAP1 has been shown to mediate the activation of c-MYC by destabilizing MAD1, a key antagonist of c-MYC. Here we developed a high-throughput assay for cIAP1 ubiquitination and identified D19, a small-molecule inhibitor of E3 ligase activity of cIAP1. We show that D19 binds to the RING domain of cIAP1 and inhibits the E3 ligase activity of cIAP1 by interfering with the dynamics of its interaction with E2. Blocking cIAP1 with D19 antagonizes c-MYC by stabilizing MAD1 protein in cells. Furthermore, we show that D19 and an improved analog (D19-14) promote c-MYC degradation and inhibit the oncogenic function of c-MYC in cells and xenograft animal models. In contrast, we show that activating E3 ubiquitin ligase activity of cIAP1 by Smac mimetics destabilizes MAD1, the antagonist of MYC, and increases the protein levels of c-MYC. Our study provides an interesting example using chemical biological approaches for determining distinct biological consequences from inhibiting vs. activating an E3 ubiquitin ligase and suggests a potential broad therapeutic strategy for targeting c-MYC in cancer treatment by pharmacologically modulating cIAP1 E3 ligase activity.

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Zhang, Gui, Yunfang Zhang, Luxuan Chen, Langxia Liu i Xuejuan Gao. "E3 ubiquitin ligase-dependent regulatory mechanism of TRIM family in carcinogenesis". Cancer Insight 2, nr 1 (28.06.2023): 102–30. http://dx.doi.org/10.58567/ci02010007.

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Tripartite motif-containing (TRIM) proteins consist of over 80 proteins, the majority of which exhibit E3 ubiquitin ligase activity. E3 ligases have a critical role in various cellular processes by specifically recognizing and ubiquitinating substrate proteins to promote their proteasomal degradation or alter their activities. Numerous studies have indicated that TRIMs are involved in carcinogenesis through various mechanisms. However, the regulatory mechanisms delimitating TRIMs’ function as E3 ligases has not yet been specifically addressed in a previous review article. In this review, we focus on recent advancements in understanding how certain TRIMs function solely as E3 ligases during cancer cell proliferation, apoptosis, and metastasis. We comprehensively summarize the target proteins of TRIMs involved in disordered signaling pathways such as Wnt/β-catenin, PI3K/AKT, NF-κB, p53, ERK, and STAT3, as well as those regulating the cell cycle and glycolysis. Following ubiquitination modification by TRIM E3 ligases, these target proteins either undergo proteasome-mediating degradation, maintain steady levels, or get activated/inactivated. This review provides a foundation for the development of E3 ligase-based cancer treatments.

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Cerqueira, Sofia A., Min Tan, Shijun Li, Franceline Juillard, Colin E. McVey, Kenneth M. Kaye i J. Pedro Simas. "Latency-Associated Nuclear Antigen E3 Ubiquitin Ligase Activity Impacts Gammaherpesvirus-Driven Germinal Center B Cell Proliferation". Journal of Virology 90, nr 17 (15.06.2016): 7667–83. http://dx.doi.org/10.1128/jvi.00813-16.

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ABSTRACTViruses have evolved mechanisms to hijack components of cellular E3 ubiquitin ligases, thus modulating the ubiquitination pathway. However, the biological relevance of such mechanisms for viral pathogenesisin vivoremains largely unknown. Here, we utilized murid herpesvirus 4 (MuHV-4) infection of mice as a model system to address the role of MuHV-4 latency-associated nuclear antigen (mLANA) E3 ligase activity in gammaherpesvirus latent infection. We show that specific mutations in the mLANA SOCS box (V199A, V199A/L202A, or P203A/P206A) disrupted mLANA's ability to recruit Elongin C and Cullin 5, thereby impairing the formation of the Elongin BC/Cullin 5/SOCS (EC5SmLANA) complex and mLANA's E3 ligase activity on host NF-κB and Myc. Although these mutations resulted in considerably reduced mLANA binding to viral terminal repeat DNA as assessed by electrophoretic mobility shift assay (EMSA), the mutations did not disrupt mLANA's ability to mediate episome persistence.In vivo, MuHV-4 recombinant viruses bearing these mLANA SOCS box mutations exhibited a deficit in latency amplification in germinal center (GC) B cells. These findings demonstrate that the E3 ligase activity of mLANA contributes to gammaherpesvirus-driven GC B cell proliferation. Hence, pharmacological inhibition of viral E3 ligase activity through targeting SOCS box motifs is a putative strategy to control gammaherpesvirus-driven lymphoproliferation and associated disease.IMPORTANCEThe gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) cause lifelong persistent infection and play causative roles in several human malignancies. Colonization of B cells is crucial for virus persistence, and access to the B cell compartment is gained by virus-driven proliferation in germinal center (GC) B cells. Infection of B cells is predominantly latent, with the viral genome persisting as a multicopy episome and expressing only a small subset of viral genes. Here, we focused on latency-associated nuclear antigen (mLANA) encoded by murid herpesvirus-4 (MuHV-4), which exhibits homology in sequence, structure, and function to KSHV LANA (kLANA), thereby allowing the study of LANA-mediated pathogenesis in mice. Our experiments show that mLANA's E3 ubiquitin ligase activity is necessary for efficient expansion of latency in GC B cells, suggesting that the development of pharmacological inhibitors of LANA E3 ubiquitin ligase activity may allow strategies to interfere with gammaherpesvirus-driven lymphoproliferation and associated disease.

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Behera, Adaitya Prasad, Pritam Naskar, Shubhangi Agarwal, Prerana Agarwal Banka, Asim Poddar i Ajit B. Datta. "Structural insights into the nanomolar affinity of RING E3 ligase ZNRF1 for Ube2N and its functional implications". Biochemical Journal 475, nr 9 (9.05.2018): 1569–82. http://dx.doi.org/10.1042/bcj20170909.

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RING (Really Interesting New Gene) domains in ubiquitin RING E3 ligases exclusively engage ubiquitin (Ub)-loaded E2s to facilitate ubiquitination of their substrates. Despite such specificity, all RINGs characterized till date bind unloaded E2s with dissociation constants (Kds) in the micromolar to the sub-millimolar range. Here, we show that the RING domain of E3 ligase ZNRF1, an essential E3 ligase implicated in diverse cellular pathways, binds Ube2N with a Kd of ∼50 nM. This high-affinity interaction is exclusive for Ube2N as ZNRF1 interacts with Ube2D2 with a Kd of ∼1 µM, alike few other E3s. The crystal structure of ZNRF1 C-terminal domain in complex with Ube2N coupled with mutational analyses reveals the molecular basis of this unusual affinity. We further demonstrate that the ubiquitination efficiency of ZNRF1 : E2 pairs correlates with their affinity. Intriguingly, as a consequence of its high E2 affinity, an excess of ZNRF1 inhibits Ube2N-mediated ubiquitination at concentrations ≥500 nM instead of showing enhanced ubiquitination. This suggests a novel mode of activity regulation of E3 ligases and emphasizes the importance of E3-E2 balance for the optimum activity. Based on our results, we propose that overexpression-based functional analyses on E3 ligases such as ZNRF1 must be approached with caution as enhanced cellular levels might result in aberrant modification activity.

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Lama, Rati, Samuel L. Galster, Chao Xu, Luke W. Davison, Sherry R. Chemler i Xinjiang Wang. "Dual Targeting of MDM4 and FTH1 by MMRi71 for Induced Protein Degradation and p53-Independent Apoptosis in Leukemia Cells". Molecules 27, nr 22 (8.11.2022): 7665. http://dx.doi.org/10.3390/molecules27227665.

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MDM2 and MDM4 are cancer drug targets validated in multiple models for p53-based cancer therapies. The RING domains of MDM2 and non-p53-binder MDM2 splice isoforms form RING domain heterodimer polyubiquitin E3 ligases with MDM4, which regulate p53 stability in vivo and promote tumorigenesis independent of p53. Despite the importance of the MDM2 RING domain in p53 regulation and cancer development, small molecule inhibitors targeting the E3 ligase activity of MDM2-MDM4 are poorly explored. Here, we describe the synthesis and characterization of quinolinol derivatives for the identification of analogs that are capable of targeting the MDM2-MDM4 heterodimer E3 ligase and inducing apoptosis in cells. The structure-activity-relationship (SAR) study identified structural moieties critical for the inhibitory effects toward MDM2-MDM4 E3 ligase, the targeted degradation of MDM4 and FTH1 in cells, and anti-proliferation activity. Lead optimization led to the development of compound MMRi71 with improved activity. In addition to accumulating p53 proteins in wt-p53 bearing cancer cells as expected of any MDM2 inhibitors, MMRi71 effectively kills p53-null leukemia cells, an activity that conventional MDM2-p53 disrupting inhibitors lack. This study provides a prototype structure for developing MDM4/FTH1 dual-targeting inhibitors as potential cancer therapeutics.

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Chu, Y., i X. Yang. "SUMO E3 ligase activity of TRIM proteins". Oncogene 30, nr 9 (25.10.2010): 1108–16. http://dx.doi.org/10.1038/onc.2010.462.

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Walden, Helen, i R. Julio Martinez-Torres. "Regulation of Parkin E3 ubiquitin ligase activity". Cellular and Molecular Life Sciences 69, nr 18 (19.04.2012): 3053–67. http://dx.doi.org/10.1007/s00018-012-0978-5.

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Chinnam, Meenalakshmi, Rati Lama, Chao Xu, Xiaojing Zhang, Carlos Cedeno, Yanqing Wang, Aimee B. Stablewski, David W. Goodrich i Xinjiang Wang. "Abstract 2606: Requirement of MDM2 E3 ligase activity for regulating p53 during normal development, cell cycle regulation and genome integrity". Cancer Research 83, nr 7_Supplement (4.04.2023): 2606. http://dx.doi.org/10.1158/1538-7445.am2023-2606.

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Abstract p53 tumor suppressor, the most mutated gene in human cancer, is negatively regulated by MDM2 and MDM4 proteins. Two distinct mechanisms of MDM2/MDM4 regulation of p53 include, one, suppression of p53 transactivation activity by direct interaction of MDM2/MDM4 with p53 protein, thus blocking its transactivation interface and two, targeting p53 to proteasomal degradation by MDM2 E3 ligase activity. However, the importance of these mechanisms in normal p53 regulation in vivo has remained controversial. To genetically separate these two mechanisms of p53 regulation we generated a novel Mdm2 mutant mouse (Mdm2L466A) that lacks E3 ligase activity but retains the ability of Mdm2 to heterodimerize with Mdm4 and inhibit p53 transactivation. Homozygous Mdm2L466A mice are embryonic lethal due to dysregulated p53 activity, thus demonstrating Mdm2 E3 ligase mediated regulation of p53 is essential during embryonic development. Additionally, we uncovered novel p53-independent functions of MDM2 E3 ligase in cell cycle regulation and genome integrity in cells. Cells lacking MDM2 E3 ligase activity have defective G2-M transition during cell cycle and developed elevated levels of aneuploidy regardless of p53 status. This study unequivocally demonstrates the requirement of Mdm2 E3 ligase activity for normal regulation of p53 and uncovers previously unknown p53-independent role of Mdm2 in cell cycle regulation and maintaining genome integrity. A current therapeutic approach involves blocking MDM2-p53 interaction to promote p53 tumor suppression function in cancer cells. Our findings suggest that this approach alone is insufficient because MDM2 has other potential oncogenic mechanisms independent of its role as negative regulator of p53. Hence, targeting MDM2 E3 ligase activity is likely to be more effective cancer therapy as it addresses both p53-dependent and p53-independent oncogenic mechanisms of MDM2. Citation Format: Meenalakshmi Chinnam, Rati Lama, Chao Xu, Xiaojing Zhang, Carlos Cedeno, Yanqing Wang, Aimee B. Stablewski, David W. Goodrich, Xinjiang Wang. Requirement of MDM2 E3 ligase activity for regulating p53 during normal development, cell cycle regulation and genome integrity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2606.

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Nurieva, Roza, Junmei Wang i Andrei Alekseev. "Essential role of E3 ubiquitin ligase activity of GRAIL in T cell functions (P1111)". Journal of Immunology 190, nr 1_Supplement (1.05.2013): 122.7. http://dx.doi.org/10.4049/jimmunol.190.supp.122.7.

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Abstract T cells are the master regulators of adaptive immune responses, and many autoimmune diseases arise due to a breakdown of self-tolerance in T cells. Understanding of the molecular mechanisms underlying T cell tolerance will lead to development of pharmacological approaches either to promote the tolerance state in terms of autoimmunity or to break tolerance in cancer. E3 ubiquitin ligases have been placed among the essential molecules involved in the regulation of T cell functions and T cell tolerance. We as well as other groups have reported that T cells activated in the absence of both CD28 and ICOS costimulation developed into tolerant T cells, associated with markedly upregulated expression of the E3 ubiquitin ligase GRAIL. In order to understand the physiological function of GRAIL, we generated mice deficient in Grail by replacing region that encompassing most of the RING domain and responsible for E3 ubiquitin activity. Remarkably, genetic inactivation of E3 ubiquitin ligase function of GRAIL led to T cell hyper-responsiveness to TCR/CD3z signaling and their independency to costimulation for activation. As a result, GRAIL-deficient mice were more predisposing to autoimmune diseases. On the other hand, modulation of GRAIL function helped to boost T cell immune responses to cancer, and, therefore, mediate tumor rejection. Thus, modulation of the E3 ligase activity of GRAIL might be an important approach to control T cell functions in autoimmunity or cancer.

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Lin, You-Sheng, Yung-Chi Chang, Ting-Yu Lai, Chih-Yuan Lee, Tsung-Hsien Chuang i Li-Chung Hsu. "The role of novel E3 ubiquitin ligase in the regulation of TLR3 signaling pathway". Journal of Immunology 204, nr 1_Supplement (1.05.2020): 226.26. http://dx.doi.org/10.4049/jimmunol.204.supp.226.26.

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Abstract Toll-like receptors (TLRs) are critical players in the host’s defense against infection by recognizing pathogen-associated molecular patterns (PAMPs) derived from microbes, and subsequently induce inflammatory responses, which eventually eliminate pathogens and repair damage tissues. However, excessive inflammation is detrimental to the host, and has been associated with the pathogenesis of various inflammatory and autoimmune diseases. Ubiquitination is a crucial strategy to alter protein function, expression, or cellular localization at the post-translational level, and has been shown to participate in the regulation of innate immune responses. We previously found that a novel E3 ubiquitin ligase was induced upon endosomal TLRs (TLR3/7/9) activation. In this project, we demonstrate that this E3 ubiquitin ligase negatively regulates TLR3-driven immune responses, which is dependent on its ubiquitin ligase activity. This novel E3 ubiquitin ligase controls TLR3 trafficking from the endosomes to the lysosomes for degradation. In addition, this E3 ubiquitin ligase interacts with TLR3 and promotes the ubiquitination of TLR3. We also found that lysosomal activity and intracellular pH value were altered in macrophages lacking this E3 ubiquitin ligase after poly(I:C) stimulation. Furthermore, we showed that mice with this E3 ubiquitin ligase deficiency were resistant to encephalomyocarditis virus (EMCV) infection due to enhanced type I interferon production. Our study together reveals this novel E3 ubiquitin ligase as a negative regulator of TLR3-induced inflammatory responses and proposes a novel mechanism for the termination of TLR3 signaling and immune response.

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Sicari, Daria, Janine Weber, Elena Maspero i Simona Polo. "The NEDD4 ubiquitin E3 ligase: a snapshot view of its functional activity and regulation". Biochemical Society Transactions 50, nr 1 (7.02.2022): 473–85. http://dx.doi.org/10.1042/bst20210731.

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Due to its fundamental role in all eukaryotic cells, a deeper understanding of the molecular mechanisms underlying ubiquitination is of central importance. Being responsible for chain specificity and substrate recognition, E3 ligases are the selective elements of the ubiquitination process. In this review, we discuss different cellular pathways regulated by one of the first identified E3 ligase, NEDD4, focusing on its pathophysiological role, its known targets and modulators. In addition, we highlight small molecule inhibitors that act on NEDD4 and discuss new strategies to effectively target this E3 enzyme.

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Balaji, Vishnu, i Thorsten Hoppe. "Regulation of E3 ubiquitin ligases by homotypic and heterotypic assembly". F1000Research 9 (6.02.2020): 88. http://dx.doi.org/10.12688/f1000research.21253.1.

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Protein ubiquitylation is essential for the maintenance of cellular homeostasis. E3 ubiquitin ligases are key components of the enzymatic machinery catalyzing the attachment of ubiquitin to substrate proteins. Consequently, enzymatic dysfunction has been associated with medical conditions including cancer, diabetes, and cardiovascular and neurodegenerative disorders. To safeguard substrate selection and ubiquitylation, the activity of E3 ligases is tightly regulated by post-translational modifications including phosphorylation, sumoylation, and ubiquitylation, as well as binding of alternative adaptor molecules and cofactors. Recent structural studies identified homotypic and heterotypic interactions between E3 ligases, adding another layer of control for rapid adaptation to changing environmental and physiological conditions. Here, we discuss the regulation of E3 ligase activity by combinatorial oligomerization and summarize examples of associated ubiquitylation pathways and mechanisms.

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Santini, S., V. Stagni, R. Giambruno, G. Fianco, A. Di Benedetto, M. Mottolese, M. Pellegrini i D. Barilà. "ATM kinase activity modulates ITCH E3-ubiquitin ligase activity". Oncogene 33, nr 9 (25.02.2013): 1113–23. http://dx.doi.org/10.1038/onc.2013.52.

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Eldin, Patrick, Laura Papon, Alexandra Oteiza, Emiliana Brocchi, T. Glen Lawson i Nadir Mechti. "TRIM22 E3 ubiquitin ligase activity is required to mediate antiviral activity against encephalomyocarditis virus". Journal of General Virology 90, nr 3 (1.03.2009): 536–45. http://dx.doi.org/10.1099/vir.0.006288-0.

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The interferon (IFN) system is a major effector of the innate immunity that allows time for the subsequent establishment of an adaptive immune response against a wide-range of pathogens. Their diverse biological actions are thought to be mediated by the products of specific but usually overlapping sets of cellular genes induced in the target cells. Ubiquitin ligase members of the tripartite motif (TRIM) protein family have emerged as IFN-induced proteins involved in both innate and adaptive immunity. In this report, we provide evidence that TRIM22 is a functional E3 ubiquitin ligase that is also ubiquitinated itself. We demonstrate that TRIM22 expression leads to a viral protection of HeLa cells against encephalomyocarditis virus infections. This effect is dependent upon its E3 ubiquitinating activity, since no antiviral effect was observed in cells expressing a TRIM22-deletion mutant defective in ubiquitinating activity. Consistent with this, TRIM22 interacts with the viral 3C protease (3C PRO ) and mediates its ubiquitination. Altogether, our findings demonstrate that TRIM22 E3 ubiquitin ligase activity represents a new antiviral pathway induced by IFN against picornaviruses.

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Spratt, Donald E., Helen Walden i Gary S. Shaw. "RBR E3 ubiquitin ligases: new structures, new insights, new questions". Biochemical Journal 458, nr 3 (28.02.2014): 421–37. http://dx.doi.org/10.1042/bj20140006.

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The RBR (RING-BetweenRING-RING) or TRIAD [two RING fingers and a DRIL (double RING finger linked)] E3 ubiquitin ligases comprise a group of 12 complex multidomain enzymes. This unique family of E3 ligases includes parkin, whose dysfunction is linked to the pathogenesis of early-onset Parkinson's disease, and HOIP (HOIL-1-interacting protein) and HOIL-1 (haem-oxidized IRP2 ubiquitin ligase 1), members of the LUBAC (linear ubiquitin chain assembly complex). The RBR E3 ligases share common features with both the larger RING and HECT (homologous with E6-associated protein C-terminus) E3 ligase families, directly catalysing ubiquitin transfer from an intrinsic catalytic cysteine housed in the C-terminal domain, as well as recruiting thioester-bound E2 enzymes via a RING domain. Recent three-dimensional structures and biochemical findings of the RBRs have revealed novel protein domain folds not previously envisioned and some surprising modes of regulation that have raised many questions. This has required renaming two of the domains in the RBR E3 ligases to more accurately reflect their structures and functions: the C-terminal Rcat (required-for-catalysis) domain, essential for catalytic activity, and a central BRcat (benign-catalytic) domain that adopts the same fold as the Rcat, but lacks a catalytic cysteine residue and ubiquitination activity. The present review discusses how three-dimensional structures of RBR (RING1-BRcat-Rcat) E3 ligases have provided new insights into our understanding of the biochemical mechanisms of these important enzymes in ubiquitin biology.

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Lazzari, Elisa, Medhat El-Halawany, Matteo De March, Floriana Valentino, Francesco Cantatore, Chiara Migliore, Silvia Onesti i Germana Meroni. "Analysis of the Zn-Binding Domains of TRIM32, the E3 Ubiquitin Ligase Mutated in Limb Girdle Muscular Dystrophy 2H". Cells 8, nr 3 (16.03.2019): 254. http://dx.doi.org/10.3390/cells8030254.

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Members of the tripartite motif family of E3 ubiquitin ligases are characterized by the presence of a conserved N-terminal module composed of a RING domain followed by one or two B-box domains, a coiled-coil and a variable C-terminal region. The RING and B-box are both Zn-binding domains but, while the RING is found in a large number of proteins, the B-box is exclusive to the tripartite motif (TRIM) family members in metazoans. Whereas the RING has been extensively characterized and shown to possess intrinsic E3 ligase catalytic activity, much less is known about the role of the B-box domains. In this study, we adopted an in vitro approach using recombinant point- and deletion-mutants to characterize the contribution of the TRIM32 Zn-binding domains to the activity of this E3 ligase that is altered in a genetic form of muscular dystrophy. We found that the RING domain is crucial for E3 ligase activity and E2 specificity, whereas a complete B-box domain is involved in chain assembly rate modulation. Further, in vitro, the RING domain is necessary to modulate TRIM32 oligomerization, whereas, in cells, both the RING and B-box cooperate to specify TRIM32 subcellular localization, which if altered may impact the pathogenesis of diseases.

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Riling, Christopher, Hari Kamadurai, Suresh Kumar, Claire E. O'Leary, Kuen-Phon Wu, Erica E. Manion, Mingjie Ying, Brenda A. Schulman i Paula M. Oliver. "Itch WW Domains Inhibit Its E3 Ubiquitin Ligase Activity by Blocking E2-E3 Ligase Trans-thiolation". Journal of Biological Chemistry 290, nr 39 (5.08.2015): 23875–87. http://dx.doi.org/10.1074/jbc.m115.649269.

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Gorelik, Maryna, i Sachdev S. Sidhu. "Regulation of SCF E3 ligase activity by Cand1". Biotarget 2 (czerwiec 2018): 10. http://dx.doi.org/10.21037/biotarget.2018.05.03.

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Eggleston, Angela K. "E3 ligase activity and suppression of breast cancer". Nature Structural & Molecular Biology 11, nr 1 (styczeń 2004): 8. http://dx.doi.org/10.1038/nsmb0104-8.

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Pichler, Andrea, Andreas Gast, Jacob S. Seeler, Anne Dejean i Frauke Melchior. "The Nucleoporin RanBP2 Has SUMO1 E3 Ligase Activity". Cell 108, nr 1 (styczeń 2002): 109–20. http://dx.doi.org/10.1016/s0092-8674(01)00633-x.

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Kane, Lesley A., Michael Lazarou, Adam I. Fogel, Yan Li, Koji Yamano, Shireen A. Sarraf, Soojay Banerjee i Richard J. Youle. "PINK1 phosphorylates ubiquitin to activate Parkin E3 ubiquitin ligase activity". Journal of Cell Biology 205, nr 2 (21.04.2014): 143–53. http://dx.doi.org/10.1083/jcb.201402104.

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PINK1 kinase activates the E3 ubiquitin ligase Parkin to induce selective autophagy of damaged mitochondria. However, it has been unclear how PINK1 activates and recruits Parkin to mitochondria. Although PINK1 phosphorylates Parkin, other PINK1 substrates appear to activate Parkin, as the mutation of all serine and threonine residues conserved between Drosophila and human, including Parkin S65, did not wholly impair Parkin translocation to mitochondria. Using mass spectrometry, we discovered that endogenous PINK1 phosphorylated ubiquitin at serine 65, homologous to the site phosphorylated by PINK1 in Parkin’s ubiquitin-like domain. Recombinant TcPINK1 directly phosphorylated ubiquitin and phospho-ubiquitin activated Parkin E3 ubiquitin ligase activity in cell-free assays. In cells, the phosphomimetic ubiquitin mutant S65D bound and activated Parkin. Furthermore, expression of ubiquitin S65A, a mutant that cannot be phosphorylated by PINK1, inhibited Parkin translocation to damaged mitochondria. These results explain a feed-forward mechanism of PINK1-mediated initiation of Parkin E3 ligase activity.

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Stevens, Rebecca V., Diego Esposito i Katrin Rittinger. "Characterisation of class VI TRIM RING domains: linking RING activity to C-terminal domain identity". Life Science Alliance 2, nr 3 (26.04.2019): e201900295. http://dx.doi.org/10.26508/lsa.201900295.

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TRIM E3 ubiquitin ligases regulate multiple cellular processes, and their dysfunction is linked to disease. They are characterised by a conserved N-terminal tripartite motif comprising a RING, B-box domains, and a coiled-coil region, with C-terminal domains often mediating substrate recruitment. TRIM proteins are grouped into 11 classes based on C-terminal domain identity. Class VI TRIMs, TRIM24, TRIM33, and TRIM28, have been described as transcriptional regulators, a function linked to their C-terminal plant homeodomain and bromodomain, and independent of their ubiquitination activity. It is unclear whether E3 ligase activity is regulated in family members where the C-terminal domains function independently. Here, we provide a detailed biochemical characterisation of the RING domains of class VI TRIMs and describe the solution structure of the TRIM28 RING. Our study reveals a lack of activity of the isolated RING domains, which may be linked to the absence of self-association. We propose that class VI TRIMs exist in an inactive state and require additional regulatory events to stimulate E3 ligase activity, ensuring that associated chromatin-remodelling factors are not injudiciously degraded.

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LÖSCHER, Marlies, Klaus FORTSCHEGGER, Gustav RITTER, Martina WOSTRY, Regina VOGLAUER, Johannes A. SCHMID, Steven WATTERS i in. "Interaction of U-box E3 ligase SNEV with PSMB4, the β7 subunit of the 20 S proteasome". Biochemical Journal 388, nr 2 (24.05.2005): 593–603. http://dx.doi.org/10.1042/bj20041517.

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Recognition of specific substrates for degradation by the ubiquitin–proteasome pathway is ensured by a cascade of ubiquitin transferases E1, E2 and E3. The mechanism by which the target proteins are transported to the proteasome is not clear, but two yeast E3s and one mammalian E3 ligase seem to be involved in the delivery of targets to the proteasome, by escorting them and by binding to the 19 S regulatory particle of the proteasome. In the present study, we show that SNEV (senescence evasion factor), a protein with in vitro E3 ligase activity, which is also involved in DNA repair and splicing, associates with the proteasome by directly binding to the β7 subunit of the 20 S proteasome. Upon inhibition of proteasome activity, SNEV does not accumulate within the cells although its co-localization with the proteasome increases significantly. Since immunofluorescence microscopy also shows increased co-localization of SNEV with ubiquitin after proteasome inhibition, without SNEV being ubiquitinated by itself, we suggest that SNEV shows E3 ligase activity not only in vitro but also in vivo and escorts its substrate to the proteasome. Since the yeast homologue of SNEV, Prp19, also interacts with the yeast β7 subunit of the proteasome, this mechanism seems to be conserved during evolution. Therefore these results support the hypothesis that E3 ligases might generally be involved in substrate transport to the proteasome. Additionally, our results provide the first evidence for a physical link between components of the ubiquitin–proteasome system and the spliceosome.

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Goldenberg, Seth J., Jeffrey G. Marblestone, Michael R. Mattern i Benjamin Nicholson. "Strategies for the identification of ubiquitin ligase inhibitors". Biochemical Society Transactions 38, nr 1 (19.01.2010): 132–36. http://dx.doi.org/10.1042/bst0380132.

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Dysregulation of the UPS (ubiquitin–proteasome system) has been implicated in a wide range of pathologies including cancer, neurodegeneration and viral infection. Inhibiting the proteasome has been shown to be an effective therapeutic strategy in humans; however, toxicity with this target remains high. E3s (Ub–protein ligases) represent an alternative attractive therapeutic target in the UPS. In this paper, we will discuss current platforms that report on E3 ligase activity and can detect E3 inhibitors, and underline the advantages and disadvantages of each approach.

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Medina-Medina, Ixaura, Paola García-Beltrán, Ignacio de la Mora-de la Mora, Jesús Oria-Hernández, Guy Millot, Robin Fahraeus, Horacio Reyes-Vivas, José G. Sampedro i Vanesa Olivares-Illana. "Allosteric Interactions byp53mRNA Govern HDM2 E3 Ubiquitin Ligase Specificity under Different Conditions". Molecular and Cellular Biology 36, nr 16 (23.05.2016): 2195–205. http://dx.doi.org/10.1128/mcb.00113-16.

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HDM2 and HDMX are key negative regulatory factors of the p53 tumor suppressor under normal conditions by promoting its degradation or preventing itstransactivity, respectively. It has more recently been shown that both proteins can also act as positive regulators of p53 after DNA damage. This involves phosphorylation by ATM on serine residues HDM2(S395) and HDMX(S403), promoting their respective interaction with thep53mRNA. However, the underlying molecular mechanisms of how these phosphorylation events switch HDM2 and HDMX from negative to positive regulators of p53 is not known. Our results show that these phosphorylation events reside within intrinsically disordered domains and change the conformation of the proteins. The modifications promote the exposition of N-terminal interfaces that support the formation of a new HDMX-HDM2 heterodimer independent of the C-terminal RING-RING interaction. The E3 ubiquitin ligase activity of this complex toward p53 is prevented by thep53mRNA ligand but, interestingly, does not affect the capacity to ubiquitinate HDMX and HDM2. These results show how ATM-mediated modifications of HDMX and HDM2 switch HDM2 E3 ubiquitin ligase activity away from p53 but toward HDMX and itself and illustrate how the substrate specificity of HDM2 E3 ligase activity is regulated.

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Yin, Chenlei, Ru Zhang, Yongyu Xu, Qiuyan Chen i Xin Xie. "Intact MDM2 E3 ligase activity is required for the cytosolic localization and function of β-arrestin2". Molecular Biology of the Cell 22, nr 9 (maj 2011): 1608–16. http://dx.doi.org/10.1091/mbc.e10-09-0779.

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β-arrestins are well known for their roles in desensitization and sequestration of G protein–coupled receptors. Unlike β-arrestin1, β-arrestin2 exhibits a predominant cytoplasmic distribution at steady state. However, the mechanism and functional significance underlying the regulation of β-arrestin2 subcellular localization remains undefined. Here we report that the subcellular localization and function of β-arrestin2 is tightly regulated by Mdm2 E3 ligase activity. Inhibition of Mdm2 E3 ligase activity either by expressing Mdm2 RING finger mutants or using specific Mdm2 E3 ligase inhibitor is sufficient to stabilize the Mdm2/β-arrestin2 complex and cause abnormal nuclear localization of β-arrestin2. Next we demonstrate that lysine residues at position 11 and 12 of β-arrestin2 are required for the interaction between Mdm2 RING finger mutant H457S (Mdm2H457S) and β-arrestin2, mutation of which prevents Mdm2H457S/β-arrestin2 interaction and subsequent nuclear localization of β-arrestin2. Finally, β-arrestin2–dependent signalings, such as receptor internalization and extracellular signal–regulated protein kinase activation, are found to be impaired once the β-arrestin2 is sequestered in the nuclei by Mdm2H457S. Our findings depict the essential role of Mdm2 E3 ligase activity in determining β-arrestin2 subcellular localization and corresponding signaling.

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Combs, Lauren R., Jacob Combs, Robert McKenna i Zsolt Toth. "Protein Degradation by Gammaherpesvirus RTAs: More Than Just Viral Transactivators". Viruses 15, nr 3 (11.03.2023): 730. http://dx.doi.org/10.3390/v15030730.

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Kaposi’s sarcoma-associated herpesvirus (KSHV) is a member of the Gammaherpesvirus subfamily that encodes several viral proteins with intrinsic E3 ubiquitin ligase activity or the ability to hijack host E3 ubiquitin ligases to modulate the host’s immune response and to support the viral life cycle. This review focuses specifically on how the immediate-early KSHV protein RTA (replication and transcription activator) hijacks the host’s ubiquitin–proteasome pathway (UPP) to target cellular and viral factors for protein degradation to allow for robust lytic reactivation. Notably, RTA’s targets are either potent transcription repressors or they are activators of the innate and adaptive immune response, which block the lytic cycle of the virus. This review mainly focuses on what is currently known about the role of the E3 ubiquitin ligase activity of KSHV RTA in the regulation of the KSHV life cycle, but we will also discuss the potential role of other gammaherpesviral RTA homologs in UPP-mediated protein degradation.

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Wei, Wei, Jian-ye Chen, Ze-xiang Zeng, Jian-fei Kuang, Wang-jin Lu i Wei Shan. "The Ubiquitin E3 Ligase MaLUL2 Is Involved in High Temperature-Induced Green Ripening in Banana Fruit". International Journal of Molecular Sciences 21, nr 24 (9.12.2020): 9386. http://dx.doi.org/10.3390/ijms21249386.

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Harvested banana fruit ripened under warm temperatures above 24 °C remain green peel, leading to severe economic loss. E3 ubiquitin-ligases, as the major components in the ubiquitination pathway, have been implicated to play important roles in temperature-stress responses. However, the molecular mechanism underlying high temperature-triggered stay-green ripening bananas in association with E3 ubiquitin-ligases, remains largely unknown. In this study, a RING-type E3 ubiquitin ligase termed MaLUL2, was isolated and characterized from banana fruit. The MaLUL2 gene contains 1095 nucleotides and encodes a protein with 365 amino acids. The MaLUL2 protein contains a domain associated with RING2 (DAR2) and a RING domain, which are the typical characteristics of RING-type E3 ligases. MaLUL2 expression was up-regulated during high temperature-induced green ripening. Subcellular localization showed that MaLUL2 localized in the nucleus, cytoplasm, and plasma membrane. MaLUL2 displayed E3 ubiquitin ligase activity in vitro. More importantly, transient overexpression of MaLUL2 in banana fruit peel increased the level of ubiquitination in vivo and led to a stay-green phenotype, accompanying with decreased expression of chlorophyll catabolic genes. Collectively, these findings suggest that MaLUL2 might act as a negative regulator of chlorophyll degradation and provide novel insights into the regulatory mechanism of high temperature-induced green ripening bananas.

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Okada, Maiko, Fumiaki Ohtake, Hiroyuki Nishikawa, Wenwen Wu, Yasushi Saeki, Keiji Takana i Tomohiko Ohta. "Liganded ERα Stimulates the E3 Ubiquitin Ligase Activity of UBE3C to Facilitate Cell Proliferation". Molecular Endocrinology 29, nr 11 (1.11.2015): 1646–57. http://dx.doi.org/10.1210/me.2015-1125.

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Abstract Estrogen receptor (ER)α is a well-characterized ligand-dependent transcription factor. However, the global picture of its nongenomic functions remains to be illustrated. Here, we demonstrate a novel function of ERα during mitosis that facilitates estrogen-dependent cell proliferation. An E3 ubiquitin ligase, UBE3C, was identified in an ERα complex from estrogen-treated MCF-7 breast cancer cells arrested at mitosis. UBE3C interacts with ERα during mitosis in an estrogen-dependent manner. In vitro, estrogen dramatically stimulates the E3 activity of UBE3C in the presence of ERα. This effect was inhibited by the estrogen antagonist tamoxifen. Importantly, estrogen enhances the ubiquitination of cyclin B1 (CCNB1) and destabilizes CCNB1 during mitosis in a manner dependent on endogenous UBE3C. ERα, UBE3C, and CCNB1 colocalize in prophase nuclei and at metaphase spindles before CCNB1 is degraded in anaphase. Depletion of UBE3C attenuates estrogen-dependent cell proliferation without affecting the transactivation function of ERα. Collectively, these results demonstrate a novel ligand-dependent action of ERα that stimulates the activity of an E3 ligase. The mitotic role of estrogen may contribute to its effects on proliferation in addition to its roles in target gene expression.

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Kawai, Hidehiko, Dmitri Wiederschain i Zhi-Min Yuan. "Critical Contribution of the MDM2 Acidic Domain to p53 Ubiquitination". Molecular and Cellular Biology 23, nr 14 (15.07.2003): 4939–47. http://dx.doi.org/10.1128/mcb.23.14.4939-4947.2003.

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ABSTRACT MDM2 is an E3 ubiquitin ligase that targets p53 for proteasomal degradation. Recent studies have shown, however, that the ring-finger domain (RFD) of MDM2, where the ubiquitin E3 ligase activity resides, is necessary but not sufficient for p53 ubiquitination, suggesting that an additional activity of MDM2 might be required. To test this possibility, we generated a series of MDM2/MDMX chimeric proteins to assess the contribution of each domain of MDM2 to the ubiquitination process. MDMX is a close structural homolog of MDM2 that nevertheless lacks the E3 ligase activity in vivo. We demonstrate here that MDMX gains self-ubiquitination activity and becomes extremely unstable upon introduction of the MDM2 RFD, indicating that the RFD is essential for self-ubiquitination. This MDMX chimeric protein, however, is unable to ubiquitinate p53 in vivo despite its E3 ligase activity and binding to p53, separating the self-ubiquitination activity of MDM2 from its ability to ubiquitinate p53. Significantly, fusion of the central acidic domain (AD) of MDM2 to the MDMX chimeric protein renders the protein fully capable of ubiquitinating p53, and p53 ubiquitination is associated with p53 degradation and nuclear export. Moreover, the AD mini protein expressed in trans can functionally rescue the AD-lacking MDM2 mutant, further supporting a critical role for the AD in MDM2-mediated p53 ubiquitination.

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Yang, Cheng-Wei, Yue-Zhi Lee, Hsing-Yu Hsu, Guan-Hao Zhao i Shiow-Ju Lee. "Tyrphostin AG1024 Suppresses Coronaviral Replication by Downregulating JAK1 via an IR/IGF-1R Independent Proteolysis Mediated by Ndfip1/2_NEDD4-like E3 Ligase Itch". Pharmaceuticals 15, nr 2 (17.02.2022): 241. http://dx.doi.org/10.3390/ph15020241.

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JAK1 depletion or downregulation was previously reported to account for coronavirus inhibition. Here, we found that AG1024, an IR (insulin receptor) and IGF-1R (insulin-like growth factor 1 receptor) inhibitor, diminishes JAK1 protein levels and exerts anti-coronaviral activities with EC50 values of 5.2 ± 0.3 μM against transmissible gastroenteritis coronavirus (TGEV) and 4.3 ± 0.3 μM against human flu coronavirus OC43. However, although the IR and IGF-1R signaling pathways are activated by insulin or IGF-1 in swine testis cells, they are not triggered upon TGEV infection. AG1024, therefore, inhibits coronaviral replication and downregulates JAK1 protein levels independently of IR and IGF-1R. Moreover, JAK1 proteolysis caused by AG1024 was found through activation of upstream Ndfip1/2 and its effector NEDD4-like E3 ligase Itch. In addition, ouabain, which was reported to mediate JAK1 proteolysis causing anti-coronaviral activity by activation of Ndfip1/2 and NEDD4 E3 ligase, additively inhibited anti-coronaviral activity and JAK1 diminishment in combination with AG1024. This study provides novel insights into the pharmacological effects of AG1024 and Itch E3 ligase mediated JAK1 proteolysis and identified Ndfip1/2 as a cognate effector for JAK1 proteolysis via the diversified E3 ligases NEDD4 and NEDD4-like Itch. These findings are expected to provide valued information for the future development of anti-viral agents.

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Malonis, Ryan J., Wenxiang Fu, Mark J. Jelcic, Marae Thompson, Brian S. Canter, Mary Tsikitis, Francisco J. Esteva i Irma Sánchez. "RNF11 sequestration of the E3 ligase SMURF2 on membranes antagonizes SMAD7 down-regulation of transforming growth factor β signaling". Journal of Biological Chemistry 292, nr 18 (14.03.2017): 7435–51. http://dx.doi.org/10.1074/jbc.m117.783662.

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The activity of the E3 ligase, SMURF2, is antagonized by an intramolecular, autoinhibitory interaction between its C2 and Hect domains. Relief of SMURF2 autoinhibition is induced by TGFβ and is mediated by the inhibitory SMAD, SMAD7. In a proteomic screen for endomembrane interactants of the RING-domain E3 ligase, RNF11, we identified SMURF2, among a cohort of Hect E3 ligases previously implicated in TGFβ signaling. Reconstitution of the SMURF2·RNF11 complex in vitro unexpectedly revealed robust SMURF2 E3 ligase activity, with biochemical properties previously restricted to the SMURF2·SMAD7 complex. Using in vitro binding assays, we find that RNF11 can directly compete with SMAD7 for SMURF2 and that binding is mutually exclusive and dependent on a proline-rich domain. Moreover, we found that co-expression of RNF11 and SMURF2 dramatically reduced SMURF2 ubiquitylation in the cell. This effect is strictly dependent on complex formation and sorting determinants that regulate the association of RNF11 with membranes. RNF11 is overexpressed in certain tumors, and, importantly, we found that depletion of this protein down-regulated gene expression of several TGFβ-responsive genes, dampened cell proliferation, and dramatically reduced cell migration in response to TGFβ. Our data suggest for the first time that the choice of binding partners for SMURF2 can sustain or repress TGFβ signaling, and RNF11 may promote TGFβ-induced cell migration.

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Bossuyt, Stijn N. V., A. Mattijs Punt, Ilona J. de Graaf, Janny van den Burg, Mark G. Williams, Helen Heussler, Ype Elgersma i Ben Distel. "Loss of nuclear UBE3A activity is the predominant cause of Angelman syndrome in individuals carrying UBE3A missense mutations". Human Molecular Genetics 30, nr 6 (19.02.2021): 430–42. http://dx.doi.org/10.1093/hmg/ddab050.

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Abstract Angelman syndrome (AS) is a severe neurodevelopmental disorder caused by deletion (~75%) or mutation (~10%) of the ubiquitin E3 ligase A (UBE3A) gene, which encodes a HECT type E3 ubiquitin protein ligase. Although the critical substrates of UBE3A are unknown, previous studies have suggested a critical role of nuclear UBE3A in AS pathophysiology. Here, we investigated to what extent UBE3A missense mutations disrupt UBE3A subcellular localization as well as catalytic activity, stability and protein folding. Our functional screen of 31 UBE3A missense mutants revealed that UBE3A mislocalization is the predominant cause of UBE3A dysfunction, accounting for 55% of the UBE3A mutations tested. The second major cause (29%) is a loss of E3-ubiquitin ligase activity, as assessed in an Escherichia coli in vivo ubiquitination assay. Mutations affecting catalytic activity are found not only in the catalytic HECT domain, but also in the N-terminal half of UBE3A, suggesting an important contribution of this N-terminal region to its catalytic potential. Together, our results show that loss of nuclear UBE3A E3 ligase activity is the predominant cause of UBE3A-linked AS. Moreover, our functional analysis screen allows rapid assessment of the pathogenicity of novel UBE3A missense variants which will be of particular importance when treatments for AS become available.

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Elliott, Joanne, Oonagh T. Lynch, Yvonne Suessmuth, Ping Qian, Caroline R. Boyd, James F. Burrows, Richard Buick i in. "Respiratory Syncytial Virus NS1 Protein Degrades STAT2 by Using the Elongin-Cullin E3 Ligase". Journal of Virology 81, nr 7 (24.01.2007): 3428–36. http://dx.doi.org/10.1128/jvi.02303-06.

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ABSTRACT Respiratory syncytial virus (RSV) infection causes bronchiolitis and pneumonia in infants. RSV has a linear single-stranded RNA genome encoding 11 proteins, 2 of which are nonstructural (NS1 and NS2). RSV specifically downregulates STAT2 protein expression, thus enabling the virus to evade the host type I interferon response. Degradation of STAT2 requires proteasomal activity and is dependent on the expression of RSV NS1 and NS2 (NS1/2). Here we investigate whether RSV NS proteins can assemble ubiquitin ligase (E3) enzymes to target STAT2 to the proteasome. We demonstrate that NS1 contains elongin C and cullin 2 binding consensus sequences and can interact with elongin C and cullin 2 in vitro; therefore, NS1 has the potential to act as an E3 ligase. By knocking down expression of specific endogenous E3 ligase components using small interfering RNA, NS1/2, or RSV-induced STAT2, degradation is prevented. These results indicate that E3 ligase activity is crucial for the ability of RSV to degrade STAT2. These data may provide the basis for therapeutic intervention against RSV and/or logically designed live attenuated RSV vaccines.

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Moses, Niko, Mu Zhang, Jheng-Yu Wu, Chen Hu, Shengyan Xiang, Xinran Geng, Yue Chen i in. "HDAC6 Regulates Radiosensitivity of Non-Small Cell Lung Cancer by Promoting Degradation of Chk1". Cells 9, nr 10 (4.10.2020): 2237. http://dx.doi.org/10.3390/cells9102237.

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We have previously discovered that HDAC6 regulates the DNA damage response (DDR) via modulating the homeostasis of a DNA mismatch repair protein, MSH2, through HDAC6’s ubiquitin E3 ligase activity. Here, we have reported HDAC6’s second potential E3 ligase substrate, a critical cell cycle checkpoint protein, Chk1. We have found that HDAC6 and Chk1 directly interact, and that HDAC6 ubiquitinates Chk1 in vivo and in vitro. Specifically, HDAC6 interacts with Chk1 via the DAC1 domain, which contains its ubiquitin E3 ligase activity. During the cell cycle, Chk1 protein levels fluctuate, peaking at the G2 phase, subsequently resolving via the ubiquitin-proteasome pathway, and thereby allowing cells to progress to the M phase. However, in HDAC6 knockdown non-small cell lung cancer (NSCLC) cells, Chk1 is constitutively active and fails to resolve post-ionizing radiation (IR), and this enhanced Chk1 activity leads to preferential G2 arrest in HDAC6 knockdown cells accompanied by a reduction in colony formation capacity and viability. Depletion or pharmacological inhibition of Chk1 in HDAC6 knockdown cells reverses this radiosensitive phenotype, suggesting that the radiosensitivity of HDAC6 knockdown cells is dependent on increased Chk1 kinase activity. Overall, our results highlight a novel mechanism of Chk1 regulation at the post-translational level, and a possible strategy for sensitizing NSCLC to radiation via inhibiting HDAC6’s E3 ligase activity.

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Lin, Yachun, Qinli Hu, Jia Zhou, Weixiao Yin, Deqiang Yao, Yuanyuan Shao, Yao Zhao i in. "Phytophthora sojae effector Avr1d functions as an E2 competitor and inhibits ubiquitination activity of GmPUB13 to facilitate infection". Proceedings of the National Academy of Sciences 118, nr 10 (3.03.2021): e2018312118. http://dx.doi.org/10.1073/pnas.2018312118.

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Oomycete pathogens such as Phytophthora secrete a repertoire of effectors into host cells to manipulate host immunity and benefit infection. In this study, we found that an RxLR effector, Avr1d, promoted Phytophthora sojae infection in soybean hairy roots. Using a yeast two-hybrid screen, we identified the soybean E3 ubiquitin ligase GmPUB13 as a host target for Avr1d. By coimmunoprecipitation (Co-IP), gel infiltration, and isothermal titration calorimetry (ITC) assays, we confirmed that Avr1d interacts with GmPUB13 both in vivo and in vitro. Furthermore, we found that Avr1d inhibits the E3 ligase activity of GmPUB13. The crystal structure Avr1d in complex with GmPUB13 was solved and revealed that Avr1d occupies the binding site for E2 ubiquitin conjugating enzyme on GmPUB13. In line with this, Avr1d competed with E2 ubiquitin conjugating enzymes for GmPUB13 binding in vitro, thereby decreasing the E3 ligase activity of GmPUB13. Meanwhile, we found that inactivation of the ubiquitin ligase activity of GmPUB13 stabilized GmPUB13 by blocking GmPUB13 degradation. Silencing of GmPUB13 in soybean hairy roots decreased P. sojae infection, suggesting that GmPUB13 acts as a susceptibility factor. Altogether, this study highlights a virulence mechanism of Phytophthora effectors, by which Avr1d competes with E2 for GmPUB13 binding to repress the GmPUB13 E3 ligase activity and thereby stabilizing the susceptibility factor GmPUB13 to facilitate Phytophthora infection. This study unravels the structural basis for modulation of host targets by Phytophthora effectors and will be instrumental for boosting plant resistance breeding.

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Mintis, Dimitris G., Anastasia Chasapi, Konstantinos Poulas, George Lagoumintzis i Christos T. Chasapis. "Assessing the Direct Binding of Ark-Like E3 RING Ligases to Ubiquitin and Its Implication on Their Protein Interaction Network". Molecules 25, nr 20 (19.10.2020): 4787. http://dx.doi.org/10.3390/molecules25204787.

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The ubiquitin pathway required for most proteins’ targeted degradation involves three classes of enzymes: E1-activating enzyme, E2-conjugating enzyme, and E3-ligases. The human Ark2C is the single known E3 ligase that adopts an alternative, Ub-dependent mechanism for the activation of Ub transfer in the pathway. Its RING domain binds both E2-Ub and free Ub with high affinity, resulting in a catalytic active UbR-RING-E2-UbD complex formation. We examined potential changes in the conformational plasticity of the Ark2C RING domain and its ligands in their complexed form within the ubiquitin pathway through molecular dynamics (MD). Three molecular mechanics force fields compared to previous NMR relaxation studies of RING domain of Arkadia were used for effective and accurate assessment of MDs. Our results suggest the Ark2C Ub-RING docking site has a substantial impact on maintaining the conformational rigidity of E2-E3 assembly, necessary for the E3’s catalytic activity. In the UbR-RING-E2-UbD catalytic complex, the UbR molecule was found to have greater mobility than the other Ub, bound to E2. Furthermore, network-based bioinformatics helped us identify E3 RING ligase candidates which potentially exhibit similar structural modules as Ark2C, along with predicted substrates targeted by the Ub-binding RING Ark2C. Our findings could trigger a further exploration of related unrevealed functions of various other E3 RING ligases.

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Hong, Jeongkwan, Minho Won i Hyunju Ro. "The Molecular and Pathophysiological Functions of Members of the LNX/PDZRN E3 Ubiquitin Ligase Family". Molecules 25, nr 24 (15.12.2020): 5938. http://dx.doi.org/10.3390/molecules25245938.

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The ligand of Numb protein-X (LNX) family, also known as the PDZRN family, is composed of four discrete RING-type E3 ubiquitin ligases (LNX1, LNX2, LNX3, and LNX4), and LNX5 which may not act as an E3 ubiquitin ligase owing to the lack of the RING domain. As the name implies, LNX1 and LNX2 were initially studied for exerting E3 ubiquitin ligase activity on their substrate Numb protein, whose stability was negatively regulated by LNX1 and LNX2 via the ubiquitin-proteasome pathway. LNX proteins may have versatile molecular, cellular, and developmental functions, considering the fact that besides these proteins, none of the E3 ubiquitin ligases have multiple PDZ (PSD95, DLGA, ZO-1) domains, which are regarded as important protein-interacting modules. Thus far, various proteins have been isolated as LNX-interacting proteins. Evidence from studies performed over the last two decades have suggested that members of the LNX family play various pathophysiological roles primarily by modulating the function of substrate proteins involved in several different intracellular or intercellular signaling cascades. As the binding partners of RING-type E3s, a large number of substrates of LNX proteins undergo degradation through ubiquitin-proteasome system (UPS) dependent or lysosomal pathways, potentially altering key signaling pathways. In this review, we highlight recent and relevant findings on the molecular and cellular functions of the members of the LNX family and discuss the role of the erroneous regulation of these proteins in disease progression.

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Tracz, Michał, Ireneusz Górniak, Andrzej Szczepaniak i Wojciech Białek. "E3 Ubiquitin Ligase SPL2 Is a Lanthanide-Binding Protein". International Journal of Molecular Sciences 22, nr 11 (27.05.2021): 5712. http://dx.doi.org/10.3390/ijms22115712.

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The SPL2 protein is an E3 ubiquitin ligase of unknown function. It is one of only three types of E3 ligases found in the outer membrane of plant chloroplasts. In this study, we show that the cytosolic fragment of SPL2 binds lanthanide ions, as evidenced by fluorescence measurements and circular dichroism spectroscopy. We also report that SPL2 undergoes conformational changes upon binding of both Ca2+ and La3+, as evidenced by its partial unfolding. However, these structural rearrangements do not interfere with SPL2 enzymatic activity, as the protein retains its ability to auto-ubiquitinate in vitro. The possible applications of lanthanide-based probes to identify protein interactions in vivo are also discussed. Taken together, the results of this study reveal that the SPL2 protein contains a lanthanide-binding site, showing for the first time that at least some E3 ubiquitin ligases are also capable of binding lanthanide ions.

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Uchida, Daisuke, Shigetsugu Hatakeyama, Akemi Matsushima, Hongwei Han, Satoshi Ishido, Hak Hotta, Jun Kudoh i in. "AIRE Functions As an E3 Ubiquitin Ligase". Journal of Experimental Medicine 199, nr 2 (19.01.2004): 167–72. http://dx.doi.org/10.1084/jem.20031291.

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Autoimmune regulator (AIRE) gene mutation is responsible for the development of autoimmune-polyendocrinopathy-candidiasis ectodermal dystrophy, an organ-specific autoimmune disease with monogenic autosomal recessive inheritance. AIRE is predominantly expressed in medullary epithelial cells of the thymus and is considered to play important roles in the establishment of self-tolerance. AIRE contains two plant homeodomain (PHD) domains, and the novel role of PHD as an E3 ubiquitin (Ub) ligase has just emerged. Here we show that the first PHD (PHD1) of AIRE mediates E3 ligase activity. The significance of this finding was underscored by the fact that disease-causing missense mutations in the PHD1 (C311Y and P326Q) abolished its E3 ligase activity. These results add a novel enzymatic function for AIRE and suggest an indispensable role of the Ub proteasome pathway in the establishment of self-tolerance, in which AIRE is involved.

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Lazarou, Michael, Derek P. Narendra, Seok Min Jin, Ephrem Tekle, Soojay Banerjee i Richard J. Youle. "PINK1 drives Parkin self-association and HECT-like E3 activity upstream of mitochondrial binding". Journal of Cell Biology 200, nr 2 (14.01.2013): 163–72. http://dx.doi.org/10.1083/jcb.201210111.

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Genetic studies indicate that the mitochondrial kinase PINK1 and the RING-between-RING E3 ubiquitin ligase Parkin function in the same pathway. In concurrence, mechanistic studies show that PINK1 can recruit Parkin from the cytosol to the mitochondria, increase the ubiquitination activity of Parkin, and induce Parkin-mediated mitophagy. Here, we used a cell-free assay to recapitulate PINK1-dependent activation of Parkin ubiquitination of a validated mitochondrial substrate, mitofusin 1. We show that PINK1 activated the formation of a Parkin–ubiquitin thioester intermediate, a hallmark of HECT E3 ligases, both in vitro and in vivo. Parkin HECT-like ubiquitin ligase activity was essential for PINK1-mediated Parkin translocation to mitochondria and mitophagy. Using an inactive Parkin mutant, we found that PINK1 stimulated Parkin self-association and complex formation upstream of mitochondrial translocation. Self-association occurred independent of ubiquitination activity through the RING-between-RING domain, providing mechanistic insight into how PINK1 activates Parkin.

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