Articles de revues : « Genome conformation »

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Wang, Yanbo, John Mallon, Haobo Wang, Digvijay Singh, Myung Hyun Jo, Boyang Hua, Scott Bailey et Taekjip Ha. « Real-time observation of Cas9 postcatalytic domain motions ». Proceedings of the National Academy of Sciences 118, n^o 2 (21 décembre 2020) : e2010650118. http://dx.doi.org/10.1073/pnas.2010650118.

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CRISPR-Cas9 fromStreptococcus pyogenesis an RNA-guided DNA endonuclease, which has become the most popular genome editing tool. Coordinated domain motions of Cas9 prior to DNA cleavage have been extensively characterized but our understanding of Cas9 conformations postcatalysis is limited. Because Cas9 can remain stably bound to the cleaved DNA for hours, its postcatalytic conformation may influence genome editing mechanisms. Here, we use single-molecule fluorescence resonance energy transfer to characterize the HNH domain motions of Cas9 that are coupled with cleavage activity of the target strand (TS) or nontarget strand (NTS) of DNA substrate. We reveal an NTS-cleavage-competent conformation following the HNH domain conformational activation. The 3′ flap generated by NTS cleavage can be rapidly digested by a 3′ to 5′ single-stranded DNA-specific exonuclease, indicating Cas9 exposes the 3′ flap for potential interaction with the DNA repair machinery. We find evidence that the HNH domain is highly flexible post-TS cleavage, explaining a recent observation that the HNH domain was not visible in a postcatalytic cryo-EM structure. Our results illuminate previously unappreciated regulatory roles of DNA cleavage activity on Cas9’s conformation and suggest possible biotechnological applications.

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Fujishiro, Shin, Naoko Tokuda et Masaki Sasai. « 2P267 Computational chromosome conformation sampling of human diploid genome(21B. Genome biology:Genome structure,Poster) ». Seibutsu Butsuri 54, supplement1-2 (2014) : S239. http://dx.doi.org/10.2142/biophys.54.s239_3.

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Sanford, Thomas J., Harriet V. Mears, Teodoro Fajardo, Nicolas Locker et Trevor R. Sweeney. « Circularization of flavivirus genomic RNA inhibits de novo translation initiation ». Nucleic Acids Research 47, n^o 18 (8 août 2019) : 9789–802. http://dx.doi.org/10.1093/nar/gkz686.

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Abstract Members of the Flaviviridae family, including dengue virus (DENV) and yellow fever virus, cause serious disease in humans, whilst maternal infection with Zika virus (ZIKV) can induce microcephaly in newborns. Following infection, flaviviral RNA genomes are translated to produce the viral replication machinery but must then serve as a template for the transcription of new genomes. However, the ribosome and viral polymerase proceed in opposite directions along the RNA, risking collisions and abortive replication. Whilst generally linear, flavivirus genomes can adopt a circular conformation facilitated by long-range RNA–RNA interactions, shown to be essential for replication. Using an in vitro reconstitution approach, we demonstrate that circularization inhibits de novo translation initiation on ZIKV and DENV RNA, whilst the linear conformation is translation-competent. Our results provide a mechanism to clear the viral RNA of ribosomes in order to promote efficient replication and, therefore, define opposing roles for linear and circular conformations of the flavivirus genome.

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Shepherd, Jeremiah J., Lingxi Zhou, William Arndt, Yan Zhang, W. Jim Zheng et Jijun Tang. « Exploring genomes with a game engine ». Faraday Discuss. 169 (2014) : 443–53. http://dx.doi.org/10.1039/c3fd00152k.

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More and more evidence indicates that the 3D conformation of eukaryotic genomes is a critical part of genome function. However, due to the lack of accurate and reliable 3D genome structural data, this information is largely ignored and most of these studies have to use information systems that view the DNA in a linear structure. Visualizing genomes in real time 3D can give researchers more insight, but this is fraught with hardware limitations since each element contains vast amounts of information that cannot be processed on the fly. Using a game engine and sophisticated video game visualization techniques enables us to construct a multi-platform real-time 3D genome viewer. The game engine-based viewer achieves much better rendering speed and can handle much larger amounts of data compared to our previous implementation using OpenGL. Combining this viewer with 3D genome models from experimental data could provide unprecedented opportunities to gain insight into the conformation–function relationships of a genome.

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Brigham, Benjamin S., Jonathan P. Kitzrow, Joshua-Paolo C. Reyes, Karin Musier-Forsyth et James B. Munro. « Intrinsic conformational dynamics of the HIV-1 genomic RNA 5′UTR ». Proceedings of the National Academy of Sciences 116, n^o 21 (8 mai 2019) : 10372–81. http://dx.doi.org/10.1073/pnas.1902271116.

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The highly conserved 5′ untranslated region (5′UTR) of the HIV-1 RNA genome is central to the regulation of virus replication. NMR and biochemical experiments support a model in which the 5′UTR can transition between at least two conformational states. In one state the genome remains a monomer, as the palindromic dimerization initiation site (DIS) is sequestered via base pairing to upstream sequences. In the second state, the DIS is exposed, and the genome is competent for kissing loop dimerization and packaging into assembling virions where an extended dimer is formed. According to this model the conformation of the 5′UTR determines the fate of the genome. In this work, the dynamics of this proposed conformational switch and the factors that regulate it were probed using multiple single-molecule and in-gel ensemble FRET assays. Our results show that the HIV-1 5′UTR intrinsically samples conformations that are stabilized by both viral and host factor binding. Annealing of tRNALys3, the primer for initiation of reverse transcription, can promote the kissing dimer but not the extended dimer. In contrast, HIV-1 nucleocapsid (NC) promotes formation of the extended dimer in both the absence and presence of tRNALys3. Our data are consistent with an ordered series of events that involves primer annealing, genome dimerization, and virion assembly.

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You, Chuihuai, Tianzhen Cui, Chang Zhang, Shoujian Zang, Yachun Su et Youxiong Que. « Assembly of the Complete Mitochondrial Genome of Gelsemium elegans Revealed the Existence of Homologous Conformations Generated by a Repeat Mediated Recombination ». International Journal of Molecular Sciences 24, n^o 1 (28 décembre 2022) : 527. http://dx.doi.org/10.3390/ijms24010527.

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Gelsemium elegans (G. elegans) is a Chinese medicinal plant with substantial economic and feeding values. There is a lack of detailed studies on the mitochondrial genome of G. elegans. In this study, the mitochondrial genome of G. elegans was sequenced and assembled, and its substructure was investigated. The mitochondrial genome of G. elegans is represented by two circular chromosomes of 406,009 bp in length with 33 annotated protein-coding genes, 15 tRNA genes, and three rRNA genes. We detected 145 pairs of repeats and found that four pairs of repeats could mediate the homologous recombination into one major conformation and five minor conformations, and the presence of conformations was verified by PCR amplification and Sanger sequencing. A total of 124 SSRs were identified in the G. elegans mitochondrial genome. The homologous segments between the chloroplast and mitochondrial genomes accounted for 5.85% of the mitochondrial genome. We also predicted 477 RNA potential editing sites and found that the nad4 gene was edited 38 times, which was the most frequent occurrence. Taken together, the mitochondrial genome of G. elegans was assembled and annotated. We gained a more comprehensive understanding on the genome of this medicinal plant, which is vital for its effective utilization and genetic improvement, especially for cytoplasmic male sterility breeding and evolution analysis in G. elegans.

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Gu, Bowen, Ruifan Sun, Xingqiang Fang, Jipan Zhang, Zhongquan Zhao, Deli Huang, Yuanping Zhao et Yongju Zhao. « Genome-Wide Association Study of Body Conformation Traits by Whole Genome Sequencing in Dazu Black Goats ». Animals 12, n^o 5 (23 février 2022) : 548. http://dx.doi.org/10.3390/ani12050548.

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Identifying associations between genetic markers and economic traits has practical benefits for the meat goat industry. To better understand the genomic regions and biological pathways contributing to body conformation traits of meat goats, a genome-wide association study was performed using Dazu black goats (DBGs), a Chinese indigenous goat breed. In particular, 150 DBGs were genotyped by whole-genome sequencing, and six body conformation traits, including body height (BH), body length (BL), cannon circumference (CC), chest depth (CD), chest width (CW), and heart girth (HG), were examined. In total, 53 potential SNPs were associated with these body conformation traits. A bioinformatics analysis was performed to evaluate the genes located close to the significant SNPs. Finally, 42 candidate genes (e.g., PSTPIP2, C7orf57, CCL19, FGF9, SGCG, FIGN, and SIPA1L) were identified as components of the genetic architecture underlying body conformation traits. Our results provide useful biological information for the improvement of growth performance and have practical applications for genomic selection in goats.

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Bentley, Kirsten, Jonathan P. Cook, Andrew K. Tuplin et David J. Evans. « Structural and functional analysis of the roles of the HCV 5′ NCR miR122-dependent long-range association and SLVI in genome translation and replication ». PeerJ 6 (6 novembre 2018) : e5870. http://dx.doi.org/10.7717/peerj.5870.

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The hepatitis C virus RNA genome possesses a variety of conserved structural elements, in both coding and non-coding regions, that are important for viral replication. These elements are known or predicted to modulate key life cycle events, such as translation and genome replication, some involving conformational changes induced by long-range RNA–RNA interactions. One such element is SLVI, a stem-loop (SL) structure located towards the 5′ end of the core protein-coding region. This element forms an alternative RNA–RNA interaction with complementary sequences in the 5′ untranslated regions that are independently involved in the binding of the cellular microRNA 122 (miR122). The switch between ‘open’ and ‘closed’ structures involving SLVI has previously been proposed to modulate translation, with lower translation efficiency associated with the ‘closed’ conformation. In the current study, we have used selective 2′-hydroxyl acylation analysed by primer extension to validate this RNA–RNA interaction in the absence and presence of miR122. We show that the long-range association (LRA) only forms in the absence of miR122, or otherwise requires the blocking of miR122 binding combined with substantial disruption of SLVI. Using site-directed mutations introduced to promote open or closed conformations of the LRA we demonstrate no correlation between the conformation and the translation phenotype. In addition, we observed no influence on virus replication compared to unmodified genomes. The presence of SLVI is well-documented to suppress translation, but these studies demonstrate that this is not due to its contribution to the LRA. We conclude that, although there are roles for SLVI in translation, the LRA is not a riboswitch regulating the translation and replication phenotypes of the virus.

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Tjong, Harianto, Wenyuan Li, Reza Kalhor, Chao Dai, Shengli Hao, Ke Gong, Yonggang Zhou et al. « Population-based 3D genome structure analysis reveals driving forces in spatial genome organization ». Proceedings of the National Academy of Sciences 113, n^o 12 (7 mars 2016) : E1663—E1672. http://dx.doi.org/10.1073/pnas.1512577113.

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Conformation capture technologies (e.g., Hi-C) chart physical interactions between chromatin regions on a genome-wide scale. However, the structural variability of the genome between cells poses a great challenge to interpreting ensemble-averaged Hi-C data, particularly for long-range and interchromosomal interactions. Here, we present a probabilistic approach for deconvoluting Hi-C data into a model population of distinct diploid 3D genome structures, which facilitates the detection of chromatin interactions likely to co-occur in individual cells. Our approach incorporates the stochastic nature of chromosome conformations and allows a detailed analysis of alternative chromatin structure states. For example, we predict and experimentally confirm the presence of large centromere clusters with distinct chromosome compositions varying between individual cells. The stability of these clusters varies greatly with their chromosome identities. We show that these chromosome-specific clusters can play a key role in the overall chromosome positioning in the nucleus and stabilizing specific chromatin interactions. By explicitly considering genome structural variability, our population-based method provides an important tool for revealing novel insights into the key factors shaping the spatial genome organization.

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Bolovan-Fritts, Cynthia A., Edward S. Mocarski et Jean A. Wiedeman. « Peripheral Blood CD14+ Cells From Healthy Subjects Carry a Circular Conformation of Latent Cytomegalovirus Genome ». Blood 93, n^o 1 (1 janvier 1999) : 394–98. http://dx.doi.org/10.1182/blood.v93.1.394.

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Abstract The majority of the human population harbors latent cytomegalovirus. Although CD14+ peripheral blood mononuclear cells have been implicated as sites of latency, the conformation of the latent viral genome in these cells is unknown. In this study, the conformation of viral genomic DNA was assessed in CD14+ cells from healthy virus seropositive carriers using an electrophoretic separation on native agarose gels in combination with polymerase chain reaction detection. Here we show that the viral genome migrates as a circular plasmid with a mobility equivalent to a circular 230-kb Shigella flexneri megaplasmid marker. Neither linear nor complex or integrated forms of the viral genome were detected. This report provides further evidence that the CD14+ cell population is an important site of viral latency in the naturally infected human host. Detection of the viral genome as a circular plasmid during latency suggests that this virus maintains its genome in a manner analogous to other herpesviruses where latent viral genome conformation has been studied.

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Bolovan-Fritts, Cynthia A., Edward S. Mocarski et Jean A. Wiedeman. « Peripheral Blood CD14+ Cells From Healthy Subjects Carry a Circular Conformation of Latent Cytomegalovirus Genome ». Blood 93, n^o 1 (1 janvier 1999) : 394–98. http://dx.doi.org/10.1182/blood.v93.1.394.401k44_394_398.

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The majority of the human population harbors latent cytomegalovirus. Although CD14+ peripheral blood mononuclear cells have been implicated as sites of latency, the conformation of the latent viral genome in these cells is unknown. In this study, the conformation of viral genomic DNA was assessed in CD14+ cells from healthy virus seropositive carriers using an electrophoretic separation on native agarose gels in combination with polymerase chain reaction detection. Here we show that the viral genome migrates as a circular plasmid with a mobility equivalent to a circular 230-kb Shigella flexneri megaplasmid marker. Neither linear nor complex or integrated forms of the viral genome were detected. This report provides further evidence that the CD14+ cell population is an important site of viral latency in the naturally infected human host. Detection of the viral genome as a circular plasmid during latency suggests that this virus maintains its genome in a manner analogous to other herpesviruses where latent viral genome conformation has been studied.

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Hrebík, Dominik, Tibor Füzik, Mária Gondová, Lenka Šmerdová, Athanassios Adamopoulos, Ondrej Šedo, Zbyněk Zdráhal et Pavel Plevka. « ICAM-1 induced rearrangements of capsid and genome prime rhinovirus 14 for activation and uncoating ». Proceedings of the National Academy of Sciences 118, n^o 19 (4 mai 2021) : e2024251118. http://dx.doi.org/10.1073/pnas.2024251118.

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Most rhinoviruses, which are the leading cause of the common cold, utilize intercellular adhesion molecule-1 (ICAM-1) as a receptor to infect cells. To release their genomes, rhinoviruses convert to activated particles that contain pores in the capsid, lack minor capsid protein VP4, and have an altered genome organization. The binding of rhinoviruses to ICAM-1 promotes virus activation; however, the molecular details of the process remain unknown. Here, we present the structures of virion of rhinovirus 14 and its complex with ICAM-1 determined to resolutions of 2.6 and 2.4 Å, respectively. The cryo-electron microscopy reconstruction of rhinovirus 14 virions contains the resolved density of octanucleotide segments from the RNA genome that interact with VP2 subunits. We show that the binding of ICAM-1 to rhinovirus 14 is required to prime the virus for activation and genome release at acidic pH. Formation of the rhinovirus 14–ICAM-1 complex induces conformational changes to the rhinovirus 14 capsid, including translocation of the C termini of VP4 subunits, which become poised for release through pores that open in the capsids of activated particles. VP4 subunits with altered conformation block the RNA–VP2 interactions and expose patches of positively charged residues. The conformational changes to the capsid induce the redistribution of the virus genome by altering the capsid–RNA interactions. The restructuring of the rhinovirus 14 capsid and genome prepares the virions for conversion to activated particles. The high-resolution structure of rhinovirus 14 in complex with ICAM-1 explains how the binding of uncoating receptors enables enterovirus genome release.

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Cao, Pei, Yuan Huang, Mei Zong et Zilong Xu. « De Novo Assembly and Comparative Analysis of the Complete Mitochondrial Genome of Chaenomeles speciosa (Sweet) Nakai Revealed the Existence of Two Structural Isomers ». Genes 14, n^o 2 (19 février 2023) : 526. http://dx.doi.org/10.3390/genes14020526.

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As a valuable Chinese traditional medicinal species, Chaenomeles speciosa (Sweet) Nakai (C. speciosa) is a natural resource with significant economic and ornamental value. However, its genetic information is not well understood. In this study, the complete mitochondrial genome of C. speciosa was assembled and characterized to explore the repeat sequences, recombination events, rearrangements, and IGT, to predict RNA editing sites, and to clarify the phylogenetic and evolutionary relationship. The C. speciosa mitochondrial genome was found to have two circular chromosomes as its major conformation, with a total length of 436,464 bp and 45.2% GC content. The mitochondrial genome contained 54 genes, including 33 unique protein-coding genes, 18 tRNAs, and 3 rRNA genes. Seven pairs of repeat sequences involving recombination events were analyzed. Both the repeat pairs, R1 and R2, played significant roles in mediating the major and minor conformations. In total, 18 MTPTs were identified, 6 of which were complete tRNA genes. There were 454 RNA editing sites in the 33 protein-coding sequences predicted by the PREPACT3 program. A phylogenetic analysis based on 22 species of mitochondrial genomes was constructed and indicated highly conserved PCG sequences. Synteny analyses showed extensive genomic rearrangements in the mitochondrial genome of C. speciosa and closely related species. This work is the first to report the C. speciosa mitochondrial genome, which is of great significance for conducting additional genetic studies on this organism.

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Wlasnowolski, Michal, Michal Sadowski, Tymon Czarnota, Karolina Jodkowska, Przemyslaw Szalaj, Zhonghui Tang, Yijun Ruan et Dariusz Plewczynski. « 3D-GNOME 2.0 : a three-dimensional genome modeling engine for predicting structural variation-driven alterations of chromatin spatial structure in the human genome ». Nucleic Acids Research 48, W1 (22 mai 2020) : W170—W176. http://dx.doi.org/10.1093/nar/gkaa388.

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Abstract Structural variants (SVs) that alter DNA sequence emerge as a driving force involved in the reorganisation of DNA spatial folding, thus affecting gene transcription. In this work, we describe an improved version of our integrated web service for structural modeling of three-dimensional genome (3D-GNOME), which now incorporates all types of SVs to model changes to the reference 3D conformation of chromatin. In 3D-GNOME 2.0, the default reference 3D genome structure is generated using ChIA-PET data from the GM12878 cell line and SVs data are sourced from the population-scale catalogue of SVs identified by the 1000 Genomes Consortium. However, users may also submit their own structural data to set a customized reference genome structure, and/or a custom input list of SVs. 3D-GNOME 2.0 provides novel tools to inspect, visualize and compare 3D models for regions that differ in terms of their linear genomic sequence. Contact diagrams are displayed to compare the reference 3D structure with the one altered by SVs. In our opinion, 3D-GNOME 2.0 is a unique online tool for modeling and analyzing conformational changes to the human genome induced by SVs across populations. It can be freely accessed at https://3dgnome.cent.uw.edu.pl/.

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Homma, Kengo, Hiromitsu Takahashi, Naomi Tsuburaya, Isao Naguro, Takao Fujisawa et Hidenori Ichijo. « Genome-wide siRNA screening reveals that DCAF4-mediated ubiquitination of optineurin stimulates autophagic degradation of Cu,Zn-superoxide dismutase ». Journal of Biological Chemistry 295, n^o 10 (3 février 2020) : 3148–58. http://dx.doi.org/10.1074/jbc.ra119.010239.

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Cu, Zn superoxide dismutase (SOD1) is one of the genes implicated in the devastating neurodegenerative disorder amyotrophic lateral sclerosis (ALS). Although the precise mechanisms of SOD1 mutant (SOD1mut)-induced motoneuron toxicity are still unclear, defects in SOD1 proteostasis are known to have a critical role in ALS pathogenesis. We previously reported that the SOD1mut adopts a conformation that exposes a Derlin-1–binding region (DBR) and that DBR-exposed SOD1 interacts with Derlin-1, leading to motoneuron death. We also found that an environmental change, i.e. zinc depletion, induces a conformational change in WT SOD1 (SOD1WT) to the DBR-exposed conformation, suggesting the presence of an equilibrium state between the DBR-masked and DBR-exposed states even with SOD1WT. Here, we conducted a high-throughput screening based on time-resolved FRET to further investigate the SOD1WT conformational change, and we used a genome-wide siRNA screen to search for regulators of SOD1 proteostasis. This screen yielded 30 candidate genes that maintained an absence of the DBR-exposed SOD1WT conformation. Among these genes was one encoding DDB1- and CUL4-associated factor 4 (DCAF4), a substrate receptor of the E3 ubiquitin–protein ligase complex. Of note, we found that DCAF4 mediates the ubiquitination of an ALS-associated protein and autophagy receptor, optineurin (OPTN), and facilitates autophagic degradation of DBR-exposed SOD1. In summary, our screen identifies DCAF4 as being required for proper proteostasis of DBR-exposed SOD1, which may have potential relevance for the development of therapies for managing ALS.

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Zirkel, Anne, et Argyris Papantonis. « Transcription as a force partitioning the eukaryotic genome ». Biological Chemistry 395, n^o 11 (1 novembre 2014) : 1301–5. http://dx.doi.org/10.1515/hsz-2014-0196.

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Abstract Eukaryotic genomes – until recently dealt with as if they were a cohort of linear DNA molecules – are perplexed three-dimensional structures, the exact conformation of which profoundly affects genome function. Recent advances in molecular biology and DNA sequencing technologies have led to a new understanding of the folding of chromatin in the nucleus. Changes in chromatin structure underlie deployment of new gene expression programs during development, differentiation, or disease. In this review, we revisit data pointing to, arguably, the major force that shapes genomes: transcription of DNA into RNA.

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Xiao, Ke, Dan Xiong, Gong Chen, Jinsong Yu, Yue Li, Kening Chen, Lu Zhang et al. « RUNX1-mediated alphaherpesvirus-host trans-species chromatin interaction promotes viral transcription ». Science Advances 7, n^o 26 (juin 2021) : eabf8962. http://dx.doi.org/10.1126/sciadv.abf8962.

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Like most DNA viruses, herpesviruses precisely deliver their genomes into the sophisticatedly organized nuclei of the infected host cells to initiate subsequent transcription and replication. However, it remains elusive how the viral genome specifically interacts with the host genome and hijacks host transcription machinery. Using pseudorabies virus (PRV) as model virus, we performed chromosome conformation capture assays to demonstrate a genome-wide specific trans-species chromatin interaction between the virus and host. Our data show that the PRV genome is delivered by the host DNA binding protein RUNX1 into the open chromatin and active transcription zone. This facilitates virus hijacking host RNAPII to efficiently transcribe viral genes, which is significantly inhibited by either a RUNX1 inhibitor or RNA interference. Together, these findings provide insights into the chromatin interaction between viral and host genomes and identify new areas of research to advance the understanding of herpesvirus genome transcription.

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Laflamme, Mark, et Robert W. Lee. « MITOCHONDRIAL GENOME CONFORMATION AMONG CW-GROUP CHLOROPHYCEAN ALGAE1 ». Journal of Phycology 39, n^o 1 (février 2003) : 213–20. http://dx.doi.org/10.1046/j.1529-8817.2003.02045.x.

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Laflamme, Mark, et Robert W. Lee. « MITOCHONDRIAL GENOME CONFORMATION AMONG CW-GROUP CHLOROPHYCEAN ALGAE ». Journal of Phycology 39, n^o 2 (28 mars 2003) : 462. http://dx.doi.org/10.1046/j.1529-8817.2003.392031.x.

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Totikov, Azamat, Andrey Tomarovsky, Lorena Derezanin, Olga Dudchenko, Erez Lieberman-Aiden, Klaus Koepfli et Sergei Kliver. « Chromosome-Level Genome Assemblies : Expanded Capabilities for Conservation Biology Research ». Proceedings 76, n^o 1 (2 novembre 2020) : 10. http://dx.doi.org/10.3390/iecge-07149.

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Genome assemblies are becoming increasingly important for understanding genetic diversity in threatened species. However, due to limited budgets in the area of conservation biology, genome assemblies, when available, tend to be highly fragmented with tens of thousands of scaffolds. The recent advent of high throughput chromosome conformation capture (Hi-C) makes it possible to generate more contiguous assemblies containing scaffolds that are length of entire chromosomes. Such assemblies greatly facilitate analyses and visualization of genome-wide features. We compared genetic diversity in seven threatened species that had both draft genome assemblies and newer chromosome-level assemblies available. Chromosome-level assemblies allowed better estimation of genetic diversity, localization, and, especially, visualization of low heterozygosity regions in the genomes.

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Xu, Zhichao, et Jesse R. Dixon. « Genome reconstruction and haplotype phasing using chromosome conformation capture methodologies ». Briefings in Functional Genomics 19, n^o 2 (26 décembre 2019) : 139–50. http://dx.doi.org/10.1093/bfgp/elz026.

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Abstract Genomic analysis of individuals or organisms is predicated on the availability of high-quality reference and genotype information. With the rapidly dropping costs of high-throughput DNA sequencing, this is becoming readily available for diverse organisms and for increasingly large populations of individuals. Despite these advances, there are still aspects of genome sequencing that remain challenging for existing sequencing methods. This includes the generation of long-range contiguity during genome assembly, identification of structural variants in both germline and somatic tissues, the phasing of haplotypes in diploid organisms and the resolution of genome sequence for organisms derived from complex samples. These types of information are valuable for understanding the role of genome sequence and genetic variation on genome function, and numerous approaches have been developed to address them. Recently, chromosome conformation capture (3C) experiments, such as the Hi-C assay, have emerged as powerful tools to aid in these challenges for genome reconstruction. We will review the current use of Hi-C as a tool for aiding in genome sequencing, addressing the applications, strengths, limitations and potential future directions for the use of 3C data in genome analysis. We argue that unique features of Hi-C experiments make this data type a powerful tool to address challenges in genome sequencing, and that future integration of Hi-C data with alternative sequencing assays will facilitate the continuing revolution in genomic analysis and genome sequencing.

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Nayak, Vinod, Moshe Dessau, Kaury Kucera, Karen Anthony, Michel Ledizet et Yorgo Modis. « Crystal Structure of Dengue Virus Type 1 Envelope Protein in the Postfusion Conformation and Its Implications for Membrane Fusion ». Journal of Virology 83, n^o 9 (25 février 2009) : 4338–44. http://dx.doi.org/10.1128/jvi.02574-08.

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ABSTRACT Dengue virus relies on a conformational change in its envelope protein, E, to fuse the viral lipid membrane with the endosomal membrane and thereby deliver the viral genome into the cytosol. We have determined the crystal structure of a soluble fragment E (sE) of dengue virus type 1 (DEN-1). The protein is in the postfusion conformation even though it was not exposed to a lipid membrane or detergent. At the domain I-domain III interface, 4 polar residues form a tight cluster that is absent in other flaviviral postfusion structures. Two of these residues, His-282 and His-317, are conserved in flaviviruses and are part of the “pH sensor” that triggers the fusogenic conformational change in E, at the reduced pH of the endosome. In the fusion loop, Phe-108 adopts a distinct conformation, forming additional trimer contacts and filling the bowl-shaped concavity observed at the tip of the DEN-2 sE trimer.

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Rajarajan, Prashanth, Tyler Borrman, Will Liao, Nadine Schrode, Erin Flaherty, Charlize Casiño, Samuel Powell et al. « Neuron-specific signatures in the chromosomal connectome associated with schizophrenia risk ». Science 362, n^o 6420 (13 décembre 2018) : eaat4311. http://dx.doi.org/10.1126/science.aat4311.

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To explore the developmental reorganization of the three-dimensional genome of the brain in the context of neuropsychiatric disease, we monitored chromosomal conformations in differentiating neural progenitor cells. Neuronal and glial differentiation was associated with widespread developmental remodeling of the chromosomal contact map and included interactions anchored in common variant sequences that confer heritable risk for schizophrenia. We describe cell type–specific chromosomal connectomes composed of schizophrenia risk variants and their distal targets, which altogether show enrichment for genes that regulate neuronal connectivity and chromatin remodeling, and evidence for coordinated transcriptional regulation and proteomic interaction of the participating genes. Developmentally regulated chromosomal conformation changes at schizophrenia-relevant sequences disproportionally occurred in neurons, highlighting the existence of cell type–specific disease risk vulnerabilities in spatial genome organization.

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MacKay, Kimberly, et Anthony Kusalik. « Computational methods for predicting 3D genomic organization from high-resolution chromosome conformation capture data ». Briefings in Functional Genomics 19, n^o 4 (29 avril 2020) : 292–308. http://dx.doi.org/10.1093/bfgp/elaa004.

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Abstract The advent of high-resolution chromosome conformation capture assays (such as 5C, Hi-C and Pore-C) has allowed for unprecedented sequence-level investigations into the structure–function relationship of the genome. In order to comprehensively understand this relationship, computational tools are required that utilize data generated from these assays to predict 3D genome organization (the 3D genome reconstruction problem). Many computational tools have been developed that answer this need, but a comprehensive comparison of their underlying algorithmic approaches has not been conducted. This manuscript provides a comprehensive review of the existing computational tools (from November 2006 to September 2019, inclusive) that can be used to predict 3D genome organizations from high-resolution chromosome conformation capture data. Overall, existing tools were found to use a relatively small set of algorithms from one or more of the following categories: dimensionality reduction, graph/network theory, maximum likelihood estimation (MLE) and statistical modeling. Solutions in each category are far from maturity, and the breadth and depth of various algorithmic categories have not been fully explored. While the tools for predicting 3D structure for a genomic region or single chromosome are diverse, there is a general lack of algorithmic diversity among computational tools for predicting the complete 3D genome organization from high-resolution chromosome conformation capture data.

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Su, Ying-Hsiu, Xianchao Zhang, Xiaohe Wang, Nigel W. Fraser et Timothy M. Block. « Evidence that the Immediate-Early Gene Product ICP4 Is Necessary for the Genome of the Herpes Simplex Virus Type 1 ICP4 Deletion Mutant Strain d120 To Circularize in Infected Cells ». Journal of Virology 80, n^o 23 (20 septembre 2006) : 11589–97. http://dx.doi.org/10.1128/jvi.01869-06.

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ABSTRACT Following infection, the physical state of linear herpes simplex virus (HSV) genomes may change into an “endless” or circular form. In this study, using Southern blot analysis of the HSV genome, we provide evidence that immediate-early protein ICP4 is involved in the process of converting the linear HSV-1 ICP4-deleted mutant strain d120 genome into its endless form. Under conditions where de novo viral DNA synthesis was inhibited, the genome of the ICP4 deletion mutant d120 failed to assume an endless conformation following infection of Vero cells (compared with the ability of wild-type strain KOS). This defect was reversed in the Vero-derived cell line E5, which produces the ICP4 protein, suggesting that ICP4 is necessary and sufficient to complement the d120 defect. When ICP4 protein was provided by the replication-defective DNA polymerase mutant HP66, the genomes of mutant d120 could assume an endless conformation in Vero cells. Western blot analysis using antibody specific to the ICP4 protein showed that although the d120 virions contained ICP4 protein, the majority of that ICP4 protein was in a 40-kDa truncated form, with only a small fraction present as a full-length 175-kDa protein. When expression of ICP4 protein from E5 cells was inhibited by cycloheximide, the d120 virion-associated ICP4 protein was unable to mediate endless formation after infection of E5 cells. Collectively, these data suggest that ICP4 protein has an important role in mediating the endless formation of the HSV-1 genome upon infection and that this function can be provided in trans.

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Bleker, Svenja, Michael Pawlita et Jürgen A. Kleinschmidt. « Impact of Capsid Conformation and Rep-Capsid Interactions on Adeno-Associated Virus Type 2 Genome Packaging ». Journal of Virology 80, n^o 2 (15 janvier 2006) : 810–20. http://dx.doi.org/10.1128/jvi.80.2.810-820.2006.

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ABSTRACT Single-stranded genomes of adeno-associated virus (AAV) are packaged into preformed capsids. It has been proposed that packaging is initiated by interaction of genome-bound Rep proteins to the capsid, thereby targeting the genome to the portal of encapsidation. Here we describe a panel of mutants with amino acid exchanges in the pores at the fivefold axes of symmetry on AAV2 capsids with reduced packaging and reduced Rep-capsid interaction. Mutation of two threonines at the rim of the fivefold pore nearly completely abolished Rep-capsid interaction and packaging. This suggests a Rep-binding site at the highly conserved amino acids at or close to the pores formed by the capsid protein pentamers. A different mutant (P. Wu, W. Xiao, T. Conlon, J. Hughes, M. Agbandje-McKenna, T. Ferkol, T. Flotte, and N. Muzyczka, J. Virol. 74:8635-8647, 2000) with an amino acid exchange at the interface of capsid protein pentamers led to a complete block of DNA encapsidation. Analysis of the capsid conformation of this mutant revealed that the pores at the fivefold axes were occupied by VP1/VP2 N termini, thereby preventing DNA introduction into the capsid. Nevertheless, the corresponding capsids had more Rep proteins bound than wild-type AAV, showing that correct Rep interaction with the capsid depends on a defined capsid conformation. Both mutant types together support the conclusion that the pores at the fivefold symmetry axes are involved in genome packaging and that capsid conformation-dependent Rep-capsid interactions play an essential role in the packaging process.

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Mitter, Michael, Catherina Gasser, Zsuzsanna Takacs, Christoph C. H. Langer, Wen Tang, Gregor Jessberger, Charlie T. Beales et al. « Conformation of sister chromatids in the replicated human genome ». Nature 586, n^o 7827 (23 septembre 2020) : 139–44. http://dx.doi.org/10.1038/s41586-020-2744-4.

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Teterina, Anastasia A., John H. Willis et Patrick C. Phillips. « Chromosome-Level Assembly of the Caenorhabditis remanei Genome Reveals Conserved Patterns of Nematode Genome Organization ». Genetics 214, n^o 4 (28 février 2020) : 769–80. http://dx.doi.org/10.1534/genetics.119.303018.

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The nematode Caenorhabditis elegans is one of the key model systems in biology, including possessing the first fully assembled animal genome. Whereas C. elegans is a self-reproducing hermaphrodite with fairly limited within-population variation, its relative C. remanei is an outcrossing species with much more extensive genetic variation, making it an ideal parallel model system for evolutionary genetic investigations. Here, we greatly improve on previous assemblies by generating a chromosome-level assembly of the entire C. remanei genome (124.8 Mb of total size) using long-read sequencing and chromatin conformation capture data. Like other fully assembled genomes in the genus, we find that the C. remanei genome displays a high degree of synteny with C. elegans despite multiple within-chromosome rearrangements. Both genomes have high gene density in central regions of chromosomes relative to chromosome ends and the opposite pattern for the accumulation of repetitive elements. C. elegans and C. remanei also show similar patterns of interchromosome interactions, with the central regions of chromosomes appearing to interact with one another more than the distal ends. The new C. remanei genome presented here greatly augments the use of the Caenorhabditis as a platform for comparative genomics and serves as a basis for molecular population genetics within this highly diverse species.

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Chothia, Cyrus. « Protein families in the metazoan genome ». Development 1994, Supplement (1 janvier 1994) : 27–33. http://dx.doi.org/10.1242/dev.1994.supplement.27.

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The evolution of development involves the development of new proteins. Estimates based on the initial results of the genome projects, and on the data banks of protein sequences and structures, suggest that the large majority of proteins come from no more than one thousand families. Members of a family are descended from a common ancestor. Protein families evolve by gene duplication and mutation. Mutations change the conformation of the peripheral regions of proteins; i.e. the regions that are involved, at least in part, in their function. If mutations proceed until only 20% of the residues in related proteins are identical, it is common for the conformational changes to affect half the structure. Most of the proteins involved in the interactions of cells, and in their assembly to form multicellular organisms, are mosaic proteins. These are large and have a modular structure, in that they are built of sets of homologous domains that are drawn from a relatively small number of protein families. Patthy's model for the evolution of mosaic proteins describes how they arose through the insertion of introns into genes, gene duplications and intronic recombination. The rates of progress in the genome sequencing projects, and in protein structure analyses, means that in a few years we will have a fairly complete outline description of the molecules responsible for the structure and function of organisms at several different levels of developmental complexity. This should make a major contribution to our understanding of the evolution of development.

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Li, An et Zhang. « The Dynamic 3D Genome in Gametogenesis and Early Embryonic Development ». Cells 8, n^o 8 (29 juillet 2019) : 788. http://dx.doi.org/10.3390/cells8080788.

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During gametogenesis and early embryonic development, the chromatin architecture changes dramatically, and both the transcriptomic and epigenomic landscape are comprehensively reprogrammed. Understanding these processes is the holy grail in developmental biology and a key step towards evolution. The 3D conformation of chromatin plays a central role in the organization and function of nuclei. Recently, the dynamics of chromatin structures have been profiled in many model and non-model systems, from insects to mammals, resulting in an interesting comparison. In this review, we first introduce the research methods of 3D chromatin structure with low-input material suitable for embryonic study. Then, the dynamics of 3D chromatin architectures during gametogenesis and early embryonic development is summarized and compared between species. Finally, we discuss the possible mechanisms for triggering the formation of genome 3D conformation in early development.

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Chen, Xiaoyu, Marrit Rinsma, Josephine M. Janssen, Jin Liu, Ignazio Maggio et Manuel A. F. V. Gonçalves. « Probing the impact of chromatin conformation on genome editing tools ». Nucleic Acids Research 44, n^o 13 (8 juin 2016) : 6482–92. http://dx.doi.org/10.1093/nar/gkw524.

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Mascher, Martin, Heidrun Gundlach, Axel Himmelbach, Sebastian Beier, Sven O. Twardziok, Thomas Wicker, Volodymyr Radchuk et al. « A chromosome conformation capture ordered sequence of the barley genome ». Nature 544, n^o 7651 (avril 2017) : 427–33. http://dx.doi.org/10.1038/nature22043.

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Stadhouders, Ralph, Guillaume J. Filion et Thomas Graf. « Transcription factors and 3D genome conformation in cell-fate decisions ». Nature 569, n^o 7756 (mai 2019) : 345–54. http://dx.doi.org/10.1038/s41586-019-1182-7.

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Hamaji, Takashi, Hiroko Kawai-Toyooka, Atsushi Toyoda, Yohei Minakuchi, Masahiro Suzuki, Asao Fujiyama, Hisayoshi Nozaki et David Roy Smith. « Multiple Independent Changes in Mitochondrial Genome Conformation in Chlamydomonadalean Algae ». Genome Biology and Evolution 9, n^o 4 (avril 2017) : 993–99. http://dx.doi.org/10.1093/gbe/evx060.

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Rodley, C. D. M., F. Bertels, B. Jones et J. M. O’Sullivan. « Global identification of yeast chromosome interactions using Genome conformation capture ». Fungal Genetics and Biology 46, n^o 11 (novembre 2009) : 879–86. http://dx.doi.org/10.1016/j.fgb.2009.07.006.

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Nicoletti, Chiara, Mattia Forcato et Silvio Bicciato. « Computational methods for analyzing genome-wide chromosome conformation capture data ». Current Opinion in Biotechnology 54 (décembre 2018) : 98–105. http://dx.doi.org/10.1016/j.copbio.2018.01.023.

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Nazarov, Leonid I., Mikhail V. Tamm, Vladik A. Avetisov et Sergei K. Nechaev. « A statistical model of intra-chromosome contact maps ». Soft Matter 11, n^o 5 (2015) : 1019–25. http://dx.doi.org/10.1039/c4sm02519a.

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Palermo, Giulia, Yinglong Miao, Ross C. Walker, Martin Jinek et J. Andrew McCammon. « CRISPR-Cas9 conformational activation as elucidated from enhanced molecular simulations ». Proceedings of the National Academy of Sciences 114, n^o 28 (26 juin 2017) : 7260–65. http://dx.doi.org/10.1073/pnas.1707645114.

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CRISPR-Cas9 has become a facile genome editing technology, yet the structural and mechanistic features underlying its function are unclear. Here, we perform extensive molecular simulations in an enhanced sampling regime, using a Gaussian-accelerated molecular dynamics (GaMD) methodology, which probes displacements over hundreds of microseconds to milliseconds, to reveal the conformational dynamics of the endonuclease Cas9 during its activation toward catalysis. We disclose the conformational transition of Cas9 from its apo form to the RNA-bound form, suggesting a mechanism for RNA recruitment in which the domain relocations cause the formation of a positively charged cavity for nucleic acid binding. GaMD also reveals the conformation of a catalytically competent Cas9, which is prone for catalysis and whose experimental characterization is still limited. We show that, upon DNA binding, the conformational dynamics of the HNH domain triggers the formation of the active state, explaining how the HNH domain exerts a conformational control domain over DNA cleavage [Sternberg SH et al. (2015) Nature, 527, 110–113]. These results provide atomic-level information on the molecular mechanism of CRISPR-Cas9 that will inspire future experimental investigations aimed at fully clarifying the biophysics of this unique genome editing machinery and at developing new tools for nucleic acid manipulation based on CRISPR-Cas9.

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McMurray, Michael A. « Coupling de novo protein folding with subunit exchange into pre-formed oligomeric protein complexes : the ‘heritable template’ hypothesis ». Biomolecular Concepts 7, n^o 5-6 (1 décembre 2016) : 271–81. http://dx.doi.org/10.1515/bmc-2016-0023.

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AbstractDespite remarkable advances in synthetic biology, the fact remains that it takes a living cell to make a new living cell. The information encoded in the genome is necessary to direct assembly of all cellular components, but it may not be sufficient. Some components (e.g. mitochondria) cannot be synthesized de novo, and instead require pre-existing templates, creating a fundamental continuity of life: if the template information is ever lost, the genomic code cannot suffice to ensure proper biogenesis. One type of information only incompletely encoded in the genome is the structures of macromolecular assemblies, which emerge from the conformations of the constituent molecules coupled with the ways in which these molecules interact. For many, if not most proteins, gene sequence is not the sole determinant of native conformation, particularly in the crowded cellular milieu. A partial solution to this problem lies in the functions of molecular chaperones, encoded by nearly all cellular genomes. Chaperones effectively restrict the ensemble of conformations sampled by polypeptides, promoting the acquisition of native, functional forms, but multiple proteins have evolved ways to achieve chaperone independence, perhaps by coupling folding with higher-order assembly. Here, I propose the existence of another solution: a novel mechanism of de novo folding in which the folding of specific proteins is templated by pre-folded molecules of a partner protein whose own folding also required similar templating. This hypothesis challenges prevailing paradigms by predicting that, in order to achieve a functional fold, some non-prion proteins require a seed passed down through generations.

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Vladimirova, Olga, Alessandra De Leo, Zhong Deng, Andreas Wiedmer, James Hayden et Paul M. Lieberman. « Phase separation and DAXX redistribution contribute to LANA nuclear body and KSHV genome dynamics during latency and reactivation ». PLOS Pathogens 17, n^o 1 (20 janvier 2021) : e1009231. http://dx.doi.org/10.1371/journal.ppat.1009231.

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Liquid-liquid phase separation (LLPS) can drive formation of diverse and essential macromolecular structures, including those specified by viruses. Kaposi’s Sarcoma-Associated Herpesvirus (KSHV) genomes associate with the viral encoded Latency-Associated Nuclear Antigen (LANA) to form stable nuclear bodies (NBs) during latent infection. Here, we show that LANA-NB formation and KSHV genome conformation involves LLPS. Using LLPS disrupting solvents, we show that LANA-NBs are partially disrupted, while DAXX and PML foci are highly resistant. LLPS disruption altered the LANA-dependent KSHV chromosome conformation but did not stimulate lytic reactivation. We found that LANA-NBs undergo major morphological transformation during KSHV lytic reactivation to form LANA-associated replication compartments encompassing KSHV DNA. DAXX colocalizes with the LANA-NBs during latency but is evicted from the LANA-associated lytic replication compartments. These findings indicate the LANA-NBs are dynamic super-molecular nuclear structures that partly depend on LLPS and undergo morphological transitions corresponding to the different modes of viral replication.

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Seitz, Stefan, Jelena Habjanič, Anne K. Schütz et Ralf Bartenschlager. « The Hepatitis B Virus Envelope Proteins : Molecular Gymnastics Throughout the Viral Life Cycle ». Annual Review of Virology 7, n^o 1 (29 septembre 2020) : 263–88. http://dx.doi.org/10.1146/annurev-virology-092818-015508.

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New hepatitis B virions released from infected hepatocytes are the result of an intricate maturation process that starts with the formation of the nucleocapsid providing a confined space where the viral DNA genome is synthesized via reverse transcription. Virion assembly is finalized by the enclosure of the icosahedral nucleocapsid within a heterogeneous envelope. The latter contains integral membrane proteins of three sizes, collectively known as hepatitis B surface antigen, and adopts multiple conformations in the course of the viral life cycle. The nucleocapsid conformation depends on the reverse transcription status of the genome, which in turn controls nucleocapsid interaction with the envelope proteins for virus exit. In addition, after secretion the virions undergo a distinct maturation step during which a topological switch of the large envelope protein confers infectivity. Here we review molecular determinants for envelopment and models that postulate molecular signals encoded in the capsid scaffold conducive or adverse to the recruitment of envelope proteins.

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Vermunt, Marit W., Di Zhang et Gerd A. Blobel. « The interdependence of gene-regulatory elements and the 3D genome ». Journal of Cell Biology 218, n^o 1 (15 novembre 2018) : 12–26. http://dx.doi.org/10.1083/jcb.201809040.

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Imaging studies, high-resolution chromatin conformation maps, and genome-wide occupancy data of architectural proteins have revealed that genome topology is tightly intertwined with gene expression. Cross-talk between gene-regulatory elements is often organized within insulated neighborhoods, and regulatory cues that induce transcriptional changes can reshape chromatin folding patterns and gene positioning within the nucleus. The cause–consequence relationship of genome architecture and gene expression is intricate, and its molecular mechanisms are under intense investigation. Here, we review the interdependency of transcription and genome organization with emphasis on enhancer–promoter contacts in gene regulation.

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Shao, Dan, Yu Yang, Shourong Shi et Haibing Tong. « Three-Dimensional Organization of Chicken Genome Provides Insights into Genetic Adaptation to Extreme Environments ». Genes 13, n^o 12 (9 décembre 2022) : 2317. http://dx.doi.org/10.3390/genes13122317.

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The high-throughput chromosome conformation capture (Hi-C) technique is widely used to study the functional roles of the three-dimensional (3D) architecture of genomes. However, the knowledge of the 3D genome structure and its dynamics during extreme environmental adaptations remains poor. Here, we characterized 3D genome architectures using the Hi-C technique for chicken liver cells. Upon comparing Lindian chicken (LDC) liver cells with Wenchang chicken (WCC) liver cells, we discovered that environmental adaptation contributed to the switching of A/B compartments, the reorganization of topologically associated domains (TADs), and TAD boundaries in both liver cells. In addition, the analysis of the switching of A/B compartments revealed that the switched compartmental genes (SCGs) were strongly associated with extreme environment adaption-related pathways, including tight junction, notch signaling pathway, vascular smooth muscle contraction, and the RIG-I-like receptor signaling pathway. The findings of this study advanced our understanding of the evolutionary role of chicken 3D genome architecture and its significance in genome activity and transcriptional regulation.

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Patel, Lalit R., Matti Nykter, Kexin Chen et Wei Zhang. « Cancer genome sequencing : Understanding malignancy as a disease of the genome, its conformation, and its evolution ». Cancer Letters 340, n^o 2 (novembre 2013) : 152–60. http://dx.doi.org/10.1016/j.canlet.2012.10.018.

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Swanson, Nicholas A., Chun-Feng D. Hou et Gino Cingolani. « Viral Ejection Proteins : Mosaically Conserved, Conformational Gymnasts ». Microorganisms 10, n^o 3 (24 février 2022) : 504. http://dx.doi.org/10.3390/microorganisms10030504.

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Bacterial viruses (or bacteriophages) have developed formidable ways to deliver their genetic information inside bacteria, overcoming the complexity of the bacterial-cell envelope. In short-tailed phages of the Podoviridae superfamily, genome ejection is mediated by a set of mysterious internal virion proteins, also called ejection or pilot proteins, which are required for infectivity. The ejection proteins are challenging to study due to their plastic structures and transient assembly and have remained less characterized than classical components such as the phage coat protein or terminase subunit. However, a spate of recent cryo-EM structures has elucidated key features underscoring these proteins’ assembly and conformational gymnastics that accompany their expulsion from the virion head through the portal protein channel into the host. In this review, we will use a phage-T7-centric approach to critically review the status of the literature on ejection proteins, decipher the conformational changes of T7 ejection proteins in the pre- and post-ejection conformation, and predict the conservation of these proteins in other Podoviridae. The challenge is to relate the structure of the ejection proteins to the mechanisms of genome ejection, which are exceedingly complex and use the host’s machinery.

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Stein, MaryElizabeth, et Kristin A. Eckert. « Impact of G-Quadruplexes and Chronic Inflammation on Genome Instability : Additive Effects during Carcinogenesis ». Genes 12, n^o 11 (9 novembre 2021) : 1779. http://dx.doi.org/10.3390/genes12111779.

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Genome instability is an enabling characteristic of cancer, essential for cancer cell evolution. Hotspots of genome instability, from small-scale point mutations to large-scale structural variants, are associated with sequences that potentially form non-B DNA structures. G-quadruplex (G4) forming motifs are enriched at structural variant endpoints in cancer genomes. Chronic inflammation is a physiological state underlying cancer development, and oxidative DNA damage is commonly invoked to explain how inflammation promotes genome instability. We summarize where G4s and oxidative stress overlap, with a focus on DNA replication. Guanine has low ionization potential, making G4s vulnerable to oxidative damage. Impacts to G4 structure are dependent upon lesion type, location, and G4 conformation. Occasionally, G4s pose a challenge to replicative DNA polymerases, requiring specialized DNA polymerases to maintain genome stability. Therefore, chronic inflammation creates a dual challenge for DNA polymerases to maintain genome stability: faithful G4 synthesis and bypassing unrepaired oxidative lesions. Inflammation is also accompanied by global transcriptome changes that may impact mutagenesis. Several studies suggest a regulatory role for G4s within cancer- and inflammatory-related gene promoters. We discuss the extent to which inflammation could influence gene regulation by G4s, thereby impacting genome instability, and highlight key areas for new investigation.

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Okonechnikov, Konstantin, Aylin Camgöz, Donglim Esther Park, Owen Chapman, Jens-Martin Hübner, Anne Jenseit, Abhijit Chakraborty et al. « EPEN-18. Oncogenic 3D genome conformations identify novel therapeutic targets in ependymoma ». Neuro-Oncology 24, Supplement_1 (1 juin 2022) : i42. http://dx.doi.org/10.1093/neuonc/noac079.155.

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Abstract Ependymoma (EPN) is an aggressive pediatric tumor that occurs throughout the central nervous system. The two most aggressive molecular subgroups of EPN are the supratentorial ZFTA-fusion associated group (ST-EPN-ZFTA) and the posterior fossa group A (PF-EPN-A). Although the molecular characteristics underlying the tumorigenesis of these subgroups have been extensively studied, these tumors remain difficult to treat. Hence, innovative therapeutic approaches are urgently needed. Here, we used genome-wide chromosome conformation capture (Hi-C), complemented with CTCF (insulators) and H3K27ac (active enhancers) ChIP-seq, as well as gene expression and whole-genome DNA methylation profiling in primary and relapsed EPN tumors and cell lines, to identify chromosomal rearrangements and regulatory mechanisms underlying aberrant expression of genes that are essential for EPN tumorigenesis. By integrating these heterogenous data types, we have observed the formation of new topologically associated domains (‘neo-TADs’) caused by intra- and inter-chromosomal structural variants in both tumors. In addition, we observed 3D chromatin complexes of regulatory elements, and the replacement of CTCF insulators by DNA hyper-methylation in PF-EPN-A tumors. These tumor-specific 3D genome conformations can be associated with the transcriptional upregulation of nearby genes. Through inhibition experiments we validated that these newly identified genes, including RCOR2, ITGA6, LAMC1, and ARL4C, are highly essential for the survival of patient-derived EPN cell lines in a disease subgroup-specific manner. Thus, our study identifies novel potential therapeutic vulnerabilities in EPN and extends our ability to reveal tumor-dependency genes and pathways by oncogenic 3D genome conformations even in tumors that lack known genetic alterations.

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Garcia‐Lozano, Marleny, Purushothaman Natarajan, Amnon Levi, Ramesh Katam, Carlos Lopez‐Ortiz, Padma Nimmakayala et Umesh K. Reddy. « Altered chromatin conformation and transcriptional regulation in watermelon following genome doubling ». Plant Journal 106, n^o 3 (22 avril 2021) : 588–600. http://dx.doi.org/10.1111/tpj.15256.

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Sati, Satish, et Giacomo Cavalli. « Chromosome conformation capture technologies and their impact in understanding genome function ». Chromosoma 126, n^o 1 (30 avril 2016) : 33–44. http://dx.doi.org/10.1007/s00412-016-0593-6.

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Klocko, Andrew D., Tereza Ormsby, Jonathan M. Galazka, Neena A. Leggett, Miki Uesaka, Shinji Honda, Michael Freitag et Eric U. Selker. « Normal chromosome conformation depends on subtelomeric facultative heterochromatin in Neurospora crassa ». Proceedings of the National Academy of Sciences 113, n^o 52 (16 novembre 2016) : 15048–53. http://dx.doi.org/10.1073/pnas.1615546113.

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High-throughput chromosome conformation capture (Hi-C) analyses revealed that the 3D structure of the Neurospora crassa genome is dominated by intra- and interchromosomal links between regions of heterochromatin, especially constitutive heterochromatin. Elimination of trimethylation of lysine 9 on histone H3 (H3K9me3) or its binding partner Heterochromatin Protein 1 (HP1)—both prominent features of constitutive heterochromatin—have little effect on the Hi-C pattern. It remained possible that di- or trimethylation of lysine 27 on histone H3 (H3K27me2/3), which becomes localized in regions of constitutive heterochromatin when H3K9me3 or HP1 are lost, plays a critical role in the 3D structure of the genome. We found that H3K27me2/3, catalyzed by the Polycomb Repressive Complex 2 (PRC2) member SET-7 (SET domain protein-7), does indeed play a prominent role in the Hi-C pattern of WT, but that its presence in regions normally occupied by H3K9me3 is not responsible for maintenance of the genome architecture when H3K9me3 is lost. The Hi-C pattern of a mutant defective in the PRC2 member N. crassa p55 (NPF), which is predominantly required for subtelomeric H3K27me2/3, was equivalent to that of the set-7 deletion strain, suggesting that subtelomeric facultative heterochromatin is paramount for normal chromosome conformation. Both PRC2 mutants showed decreased heterochromatin–heterochromatin contacts and increased euchromatin–heterochromatin contacts. Cytological observations suggested elimination of H3K27me2/3 leads to partial displacement of telomere clusters from the nuclear periphery. Transcriptional profiling of Δdim-5, Δset-7, Δset-7; Δdim-5, and Δnpf strains detailed anticipated changes in gene expression but did not support the idea that global changes in genome architecture, per se, led to altered transcription.

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