Articles de revues : « End-tethering »

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Solinger, Jachen A., et Anne Spang. « Loss of the Sec1/Munc18-family proteins VPS-33.2 and VPS-33.1 bypasses a block in endosome maturation in Caenorhabditis elegans ». Molecular Biology of the Cell 25, n^o 24 (décembre 2014) : 3909–25. http://dx.doi.org/10.1091/mbc.e13-12-0710.

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The end of the life of a transport vesicle requires a complex series of tethering, docking, and fusion events. Tethering complexes play a crucial role in the recognition of membrane entities and bringing them into close opposition, thereby coordinating and controlling cellular trafficking events. Here we provide a comprehensive RNA interference analysis of the CORVET and HOPS tethering complexes in metazoans. Knockdown of CORVET components promoted RAB-7 recruitment to subapical membranes, whereas in HOPS knockdowns, RAB-5 was found also on membrane structures close to the cell center, indicating the RAB conversion might be impaired in the absence of these tethering complexes. Unlike in yeast, metazoans have two VPS33 homologues, which are Sec1/Munc18 (SM)-family proteins involved in the regulation of membrane fusion. We assume that in wild type, each tethering complex contains a specific SM protein but that they may be able to substitute for each other in case of absence of the other. Of importance, knockdown of both SM proteins allowed bypass of the endosome maturation block in sand-1 mutants. We propose a model in which the SM proteins in tethering complexes are required for coordinated flux of material through the endosomal system.

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Huang, H., L. S. Penn, R. P. Quirk et T. H. Cheong. « Effect of Segmental Adsorption on the Tethering of End-Functionalized Polymer Chains ». Macromolecules 37, n^o 2 (janvier 2004) : 516–23. http://dx.doi.org/10.1021/ma030333r.

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Pausch, Jonas, Tatiana Sequeira Gross, Hermann Reichenspurner et Evaldas Girdauskas. « Left ventricular reverse remodeling after successful subannular mitral valve repair in end-stage heart failure : a case report ». European Heart Journal - Case Reports 4, n^o 3 (27 avril 2020) : 1–5. http://dx.doi.org/10.1093/ehjcr/ytaa087.

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Abstract Background Due to ongoing left ventricular (LV) remodeling and consecutive geometric displacement of both papillary muscles, end-stage heart failure is frequently associated with relevant functional mitral regurgitation (FMR) Type IIIb. Treatment strategies of FMR and their prognostic impact are still controversial. Case summary We present a case of an 80-year-old patient who suffered from recurrent symptoms of congestive heart failure due to dilated cardiomyopathy and concomitant severe FMR. To specifically address severe tethering of both mitral leaflets heart team decision was to perform minimally invasive mitral valve repair (MVR) including a subannular LV remodeling procedure, instead of an interventional edge-to-edge repair (MitraClip® procedure). In addition to mitral valve ring annuloplasty, standardized relocation of both papillary muscles was performed successfully, leading to a complete resolution of mitral leaflet tethering. There were no procedural complications and the patient was discharged with an excellent functional result without residual mitral regurgitation. Furthermore, after 12 and 24 months, he reported an increase of his functional exercise capacity and a remarkable reverse LV remodeling could be demonstrated. Discussion Novel subannular repair techniques, especially the relocation of both papillary muscles, specifically address severe leaflet tethering in FMR and have an obvious potential to improve long-term competence of MVR. Therefore, they could be considered as a viable therapeutic option even in elderly patients presenting with end-stage cardiomyopathy and severe leaflet tenting.

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Deshpande, Rajashree A., Gareth J. Williams, Oliver Limbo, R. Scott Williams, Jeff Kuhnlein, Ji‐Hoon Lee, Scott Classen et al. « ATP ‐driven Rad50 conformations regulate DNA tethering, end resection, and ATM checkpoint signaling ». EMBO Journal 35, n^o 7 (avril 2016) : 791. http://dx.doi.org/10.15252/embj.201694047.

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Jain, Suvi, Neal Sugawara et James E. Haber. « Role of Double-Strand Break End-Tethering during Gene Conversion in Saccharomyces cerevisiae ». PLOS Genetics 12, n^o 4 (13 avril 2016) : e1005976. http://dx.doi.org/10.1371/journal.pgen.1005976.

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Deshpande, R. A., G. J. Williams, O. Limbo, R. S. Williams, J. Kuhnlein, J. H. Lee, S. Classen et al. « ATP-driven Rad50 conformations regulate DNA tethering, end resection, and ATM checkpoint signaling ». EMBO Journal 33, n^o 5 (3 février 2014) : 482–500. http://dx.doi.org/10.1002/embj.201386100.

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Splinter, Daniël, David S. Razafsky, Max A. Schlager, Andrea Serra-Marques, Ilya Grigoriev, Jeroen Demmers, Nanda Keijzer et al. « BICD2, dynactin, and LIS1 cooperate in regulating dynein recruitment to cellular structures ». Molecular Biology of the Cell 23, n^o 21 (novembre 2012) : 4226–41. http://dx.doi.org/10.1091/mbc.e12-03-0210.

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Cytoplasmic dynein is the major microtubule minus-end–directed cellular motor. Most dynein activities require dynactin, but the mechanisms regulating cargo-dependent dynein–dynactin interaction are poorly understood. In this study, we focus on dynein–dynactin recruitment to cargo by the conserved motor adaptor Bicaudal D2 (BICD2). We show that dynein and dynactin depend on each other for BICD2-mediated targeting to cargo and that BICD2 N-terminus (BICD2-N) strongly promotes stable interaction between dynein and dynactin both in vitro and in vivo. Direct visualization of dynein in live cells indicates that by itself the triple BICD2-N–dynein–dynactin complex is unable to interact with either cargo or microtubules. However, tethering of BICD2-N to different membranes promotes their microtubule minus-end–directed motility. We further show that LIS1 is required for dynein-mediated transport induced by membrane tethering of BICD2-N and that LIS1 contributes to dynein accumulation at microtubule plus ends and BICD2-positive cellular structures. Our results demonstrate that dynein recruitment to cargo requires concerted action of multiple dynein cofactors.

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Novick, P., M. Medkova, G. Dong, A. Hutagalung, K. Reinisch et B. Grosshans. « Interactions between Rabs, tethers, SNAREs and their regulators in exocytosis ». Biochemical Society Transactions 34, n^o 5 (1 octobre 2006) : 683–86. http://dx.doi.org/10.1042/bst0340683.

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Sec2p is the exchange factor that activates Sec4p, the Rab GTPase controlling the final stage of the yeast exocytic pathway. Sec2p is recruited to secretory vesicles by Ypt32-GTP, a Rab controlling exit from the Golgi. Sec15p, a subunit of the octameric exocyst tethering complex and an effector of Sec4p, binds to Sec2p on secretory vesicles, displacing Ypt32p. Sec2p mutants defective in the region 450–508 amino acids bind to Sec15p more tightly. In these mutants, Sec2p accumulates in the cytosol in a complex with the exocyst and is not recruited to vesicles by Ypt32p. Thus the region 450–508 amino acids negatively regulates the association of Sec2p with the exocyst, allowing it to recycle on to new vesicles. The structures of one nearly full-length exocyst subunit and three partial subunits have been determined and, despite very low sequence identity, all form rod-like structures built of helical bundles stacked end to end. These rods may bind to each other along their sides to form the assembled complex. While Sec15p binds Sec4-GTP on the vesicle, other subunits bind Rho GTPases on the plasma membrane, thus tethering vesicles to exocytic sites. Sec4-GTP also binds Sro7p, a yeast homologue of the Drosophila lgl (lethal giant larvae) tumour suppressor. Sro7 also binds to Sec9p, a SNAP25 (25 kDa synaptosome-associated protein)-like t-SNARE [target-membrane-associated SNARE (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor)], and can form a Sec4p–Sro7p–Sec9p ternary complex. Overexpression of Sec4p, Sro7p or Sec1p (another SNARE regulator) can bypass deletions of three different exocyst subunits. Thus promoting SNARE function can compensate for tethering defects.

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Brown, Robert H., et Wayne Mitzner. « Airway closure with high PEEP in vivo ». Journal of Applied Physiology 89, n^o 3 (1 septembre 2000) : 956–60. http://dx.doi.org/10.1152/jappl.2000.89.3.956.

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When airway smooth muscle is contracted in vitro, the airway lumen continues to narrow with increasing concentrations of agonist until complete airway closure occurs. Although there remains some controversy regarding whether airways can close in vivo, recent work has clearly demonstrated that, if the airway is sufficiently stimulated with contractile agonists, complete closure of even large cartilaginous conducting airways can readily occur with the lung at functional residual capacity (Brown RH and Mitzner W. J Appl Physiol 85: 2012–2017, 1998). This result suggests that the tethering of airways in situ by parenchymal attachments is small at functional residual capacity. However, at lung volumes above functional residual capacity, the outward tethering of airways should increase, because both the parenchymal shear modulus and tethering forces increase in proportion to the transpulmonary pressure. In the present study, we tested whether we could prevent airway closure in vivo by increasing lung volume with positive end-expiratory pressure (PEEP). Airway smooth muscle was stimulated with increasing methacholine doses delivered directly to airway smooth muscle at three levels of PEEP (0, 6, and 10 cmH2O). Our results show that increased lung volume shifted the airway methacholine dose-response curve to the right, but, in many airways in most animals, airway closure still occurred even at the highest levels of PEEP.

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Blaustein, Robert O. « Kinetics of Tethering Quaternary Ammonium Compounds to K+ Channels ». Journal of General Physiology 120, n^o 2 (30 juillet 2002) : 203–16. http://dx.doi.org/10.1085/jgp.20028613.

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Polymeric maleimido–quaternary ammonium (QA) compounds have been shown to function as molecular tape measures when covalently tethered to external cysteine residues of a Shaker K+ channel (Blaustein R.O., P.A. Cole, C. Williams, and C. Miller. 2000. Nat. Struct. Biol. 7:309–311). For sufficiently long compounds, the cysteine–maleimide tethering reaction creates a high concentration, at the channel's pore, of a TEA-like moiety that irreversibly blocks current. This paper investigates a striking feature of the maleimide–cysteine tethering kinetics. Strong blockers—those that induce substantial levels (>80%) of irreversible inhibition of current—react with channel cysteines much more rapidly than weak blockers and, when delivered to channels with four cysteine targets, react with multiexponential kinetics. This behavior is shown to arise from the ability of a strong blocker to concentrate its maleimide end near a channel's cysteine target by exploiting the reversible pore-blocking affinity of its QA headgroup.

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McHugh, Toni, Agata A. Gluszek et Julie P. I. Welburn. « Microtubule end tethering of a processive kinesin-8 motor Kif18b is required for spindle positioning ». Journal of Cell Biology 217, n^o 7 (16 avril 2018) : 2403–16. http://dx.doi.org/10.1083/jcb.201705209.

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Mitotic spindle positioning specifies the plane of cell division during anaphase. Spindle orientation and positioning are therefore critical to ensure symmetric division in mitosis and asymmetric division during development. The control of astral microtubule length plays an essential role in positioning the spindle. In this study, using gene knockout, we show that the kinesin-8 Kif18b controls microtubule length to center the mitotic spindle at metaphase. Using in vitro reconstitution, we reveal that Kif18b is a highly processive plus end–directed motor that uses a C-terminal nonmotor microtubule-binding region to accumulate at growing microtubule plus ends. This region is regulated by phosphorylation to spatially control Kif18b accumulation at plus ends and is essential for Kif18b-dependent spindle positioning and regulation of microtubule length. Finally, we demonstrate that Kif18b shortens microtubules by increasing the catastrophe rate of dynamic microtubules. Overall, our work reveals that Kif18b uses its motile properties to reach microtubule ends, where it regulates astral microtubule length to ensure spindle centering.

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Cassani, Corinne, Elisa Gobbini, Jacopo Vertemara, Weibin Wang, Antonio Marsella, Patrick Sung, Renata Tisi, Giuseppe Zampella et Maria Pia Longhese. « Structurally distinct Mre11 domains mediate MRX functions in resection, end-tethering and DNA damage resistance ». Nucleic Acids Research 46, n^o 6 (6 février 2018) : 2990–3008. http://dx.doi.org/10.1093/nar/gky086.

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Tardy, Blaise L., Joseph J. Richardson, Vichida Nithipipat, Kristian Kempe, Junling Guo, Kwun Lun Cho, Md Arifur Rahim, Hirotaka Ejima et Frank Caruso. « Protein Adsorption and Coordination-Based End-Tethering of Functional Polymers on Metal–Phenolic Network Films ». Biomacromolecules 20, n^o 3 (22 février 2019) : 1421–28. http://dx.doi.org/10.1021/acs.biomac.9b00006.

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Niu, Xiaojia, Fan Zheng et Chuanhai Fu. « The concerted actions of Tip1/CLIP-170, Klp5/Kinesin-8, and Alp14/XMAP215 regulate microtubule catastrophe at the cell end ». Journal of Molecular Cell Biology 11, n^o 11 (9 mai 2019) : 956–66. http://dx.doi.org/10.1093/jmcb/mjz039.

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Abstract Spatial regulation of microtubule catastrophe is important for controlling microtubule length and consequently contributes to the proper establishment of cell polarity and cell growth. The +TIP proteins including Tip1/CLIP-170, Klp5/Kinesin-8, and Alp14/XMAP215 reside at microtubule plus ends to regulate microtubule dynamics. In the fission yeast Schizosaccharomyces pombe, Tip1 and Alp14 serve as microtubule-stabilizing factors, while Klp5 functions oppositely as a catastrophe-promoting factor. Despite that Tip1 has been shown to play a key role in restricting microtubule catastrophe to the cell end, how Tip1 fulfills the role remains to be determined. Employing live-cell microscopy, we showed that the absence of Tip1 impairs the localization of both Klp5 and Alp14 at microtubule plus ends, but the absence of Klp5 prolongs the residence time of Tip1 at microtubule plus ends. We further revealed that Klp5 accumulates behind Tip1 at microtubule plus ends in a Tip1-dependent manner. In addition, artificially tethering Klp5 to microtubule plus ends promotes premature microtubule catastrophe, while tethering Alp14 to microtubule plus ends in the cells lacking Tip1 rescues the phenotype of short microtubules. These findings establish that Tip1 restricts microtubule catastrophe to the cell end likely by spatially restricting the microtubule catastrophe activity of Klp5 and stabilizing Alp14 at microtubule plus ends. Thus, the work demonstrates the orchestration of Tip1, Alp14, and Klp5 in ensuring microtubule catastrophe at the cell end.

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Waithaka, Albina, Olena Maiakovska, Dirk Grimm, Larissa Melo do Nascimento et Christine Clayton. « Sequences and proteins that influence mRNA processing in Trypanosoma brucei : Evolutionary conservation of SR-domain and PTB protein functions ». PLOS Neglected Tropical Diseases 16, n^o 10 (26 octobre 2022) : e0010876. http://dx.doi.org/10.1371/journal.pntd.0010876.

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Background Spliced leader trans splicing is the addition of a short, capped sequence to the 5’ end of mRNAs. It is widespread in eukaryotic evolution, but factors that influence trans splicing acceptor site choice have been little investigated. In Kinetoplastids, all protein-coding mRNAs are 5’ trans spliced. A polypyrimidine tract is usually found upstream of the AG splice acceptor, but there is no branch point consensus; moreover, splicing dictates polyadenylation of the preceding mRNA, which is a validated drug target. Methodology and principal findings We here describe a trans splicing reporter system that can be used for studies and screens concerning the roles of sequences and proteins in processing site choice and efficiency. Splicing was poor with poly(U) tracts less than 9 nt long, and was influenced by an intergenic region secondary structure. A screen for signals resulted in selection of sequences that were on average 45% U and 35% C. Tethering of either the splicing factor SF1, or the cleavage and polyadenylation factor CPSF3 within the intron stimulated processing in the correct positions, while tethering of two possible homologues of Opisthokont PTB inhibited processing. In contrast, tethering of SR-domain proteins RBSR1, RBSR2, or TSR1 or its interaction partner TSR1IP, promoted use of alternative signals upstream of the tethering sites. RBSR1 interacts predominantly with proteins implicated in splicing, whereas the interactome of RBSR2 is more diverse. Conclusions Our selectable constructs are suitable for screens of both sequences, and proteins that affect mRNA processing in T. brucei. Our results suggest that the functions of PTB and SR-domain proteins in splice site definition may already have been present in the last eukaryotic common ancestor tract binding protein, SR-domain protein.

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Wei, Wei-Li, Qiushui Chen, Haifang Li et Jin-Ming Lin. « Self-Assemblies of Single-Walled Carbon Nanotubes through Tunable Tethering of Pyrenes by Dextrin for Rapidly Chiral Sensing ». International Journal of Analytical Chemistry 2011 (2011) : 1–10. http://dx.doi.org/10.1155/2011/862692.

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Pyrene-modified dextrin (Py-Dex) was synthesized via the Schiff base reaction between reducing end of dextrins and 1-aminopyrene, and then self-assemblies of single-walled carbon nanotubes (SWNTs) were fabricated through the tunable tethering of pyrene to SWNTs by dextrin chains. The Py-Dex-SWNTs assemblies were found to be significantly water-soluble because of the synergistic effect of dextrin chains and pyrene moieties. Py-Dex and Py-Dex-SWNTs were adequately characterized by NMR, UV-vis, fluorescence spectroscopy, Raman spectroscopy, matrix-assisted laser desorption/ionization-time of flight mass spectroscopy, and transmission electron microscopy. The tethering effect of dextrin toward pyrene moieties was clearly revealed and was found to be tunable by adjusting the length of dextrin chains. The fluorescence of pyrene moieties was sufficiently quenched by SWNTs with the support of dextrin chains. Furthermore, the Py-Dex-SWNTs assemblies were used for chiral selective sensing by introducing cyclodextrins as chiral binding sites. The rapid chiral sensing was successfully tested for different enantiomers.

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Cassani, Corinne, Elisa Gobbini, Weibin Wang, Hengyao Niu, Michela Clerici, Patrick Sung et Maria Pia Longhese. « Tel1 and Rif2 Regulate MRX Functions in End-Tethering and Repair of DNA Double-Strand Breaks ». PLOS Biology 14, n^o 2 (22 février 2016) : e1002387. http://dx.doi.org/10.1371/journal.pbio.1002387.

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Tamura, Naoka, et Viji M. Draviam. « Microtubule plus-ends within a mitotic cell are ‘moving platforms’ with anchoring, signalling and force-coupling roles ». Open Biology 2, n^o 11 (novembre 2012) : 120132. http://dx.doi.org/10.1098/rsob.120132.

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The microtubule polymer grows and shrinks predominantly from one of its ends called the ‘plus-end’. Plus-end regulation during interphase is well understood. However, mitotic regulation of plus-ends is only beginning to be understood in mammalian cells. During mitosis, the plus-ends are tethered to specialized microtubule capture sites. At these sites, plus-end-binding proteins are loaded and unloaded in a regulated fashion. Proper tethering of plus-ends to specialized sites is important so that the microtubule is able to translate its growth and shrinkage into pushing and pulling forces that move bulky subcellular structures. We discuss recent advances on how mitotic plus-ends are tethered to distinct subcellular sites and how plus-end-bound proteins can modulate the forces that move subcellular structures. Using end binding 1 (EB1) as a prototype plus-end-binding protein, we highlight the complex network of plus-end-binding proteins and their regulation through phosphorylation. Finally, we develop a speculative ‘moving platform’ model that illustrates the plus-end's role in distinguishing correct versus incorrect microtubule interactions.

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Stumpff, Jason, Yaqing Du, Chauca A. English, Zoltan Maliga, Michael Wagenbach, Charles L. Asbury, Linda Wordeman et Ryoma Ohi. « A Tethering Mechanism Controls the Processivity and Kinetochore-Microtubule Plus-End Enrichment of the Kinesin-8 Kif18A ». Molecular Cell 43, n^o 5 (septembre 2011) : 764–75. http://dx.doi.org/10.1016/j.molcel.2011.07.022.

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Uchiyama, Keiji, Eija Jokitalo, Mervi Lindman, Mark Jackman, Fumi Kano, Masayuki Murata, Xiaodong Zhang et Hisao Kondo. « The localization and phosphorylation of p47 are important for Golgi disassembly–assembly during the cell cycle ». Journal of Cell Biology 161, n^o 6 (16 juin 2003) : 1067–79. http://dx.doi.org/10.1083/jcb.200303048.

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In mammalian cells, the Golgi apparatus is disassembled at the onset of mitosis and reassembled at the end of mitosis. This disassembly–reassembly is generally believed to be essential for the equal partitioning of Golgi into two daughter cells. For Golgi disassembly, membrane fusion, which is mediated by NSF and p97, needs to be blocked. For the NSF pathway, the tethering of p115-GM130 is disrupted by the mitotic phosphorylation of GM130, resulting in the inhibition of NSF-mediated fusion. In contrast, the p97/p47 pathway does not require p115-GM130 tethering, and its mitotic inhibitory mechanism has been unclear. Now, we have found that p47, which mainly localizes to the nucleus during interphase, is phosphorylated on Serine-140 by Cdc2 at mitosis. The phosphorylated p47 does not bind to Golgi membranes. An in vitro assay shows that this phosphorylation is required for Golgi disassembly. Microinjection of p47(S140A), which is unable to be phosphorylated, allows the cell to keep Golgi stacks during mitosis and has no effect on the equal partitioning of Golgi into two daughter cells, suggesting that Golgi fragmentation-dispersion may not be obligatory for equal partitioning even in mammalian cells.

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Mizuno, Hiroaki, Kotaro Tanaka, Sawako Yamashiro, Akihiro Narita et Naoki Watanabe. « Helical rotation of the diaphanous-related formin mDia1 generates actin filaments resistant to cofilin ». Proceedings of the National Academy of Sciences 115, n^o 22 (14 mai 2018) : E5000—E5007. http://dx.doi.org/10.1073/pnas.1803415115.

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The complex interplay between actin regulatory proteins facilitates the formation of diverse cellular actin structures. Formin homology proteins (formins) play an essential role in the formation of actin stress fibers and yeast actin cables, to which the major actin depolymerizing factor cofilin barely associates. In vitro, F-actin decorated with cofilin exhibits a marked increase in the filament twist. On the other hand, a mammalian formin mDia1 rotates along the long-pitch actin helix during processive actin elongation (helical rotation). Helical rotation may impose torsional force on F-actin in the opposite direction of the cofilin-induced twisting. Here, we show that helical rotation of mDia1 converts F-actin resistant to cofilin both in vivo and in vitro. F-actin assembled by mDia1 without rotational freedom became more resistant to the severing and binding activities of cofilin than freely rotatable F-actin. Electron micrographic analysis revealed untwisting of the long-pitch helix of F-actin elongating from mDia1 on tethering of both mDia1 and the pointed end side of the filament. In cells, single molecules of mDia1ΔC63, an activated mutant containing N-terminal regulatory domains, showed tethering to cell structures more frequently than autoinhibited wild-type mDia1 and mDia1 devoid of N-terminal domains. Overexpression of mDia1ΔC63 induced the formation of F-actin, which has prolonged lifetime and accelerates dissociation of cofilin. Helical rotation of formins may thus serve as an F-actin stabilizing mechanism by which a barbed end-bound molecule can enhance the stability of a filament over a long range.

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Coursey, Tami L., et Alison A. McBride. « Hitchhiking of Viral Genomes on Cellular Chromosomes ». Annual Review of Virology 6, n^o 1 (29 septembre 2019) : 275–96. http://dx.doi.org/10.1146/annurev-virology-092818-015716.

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Persistent viral infections require a host cell reservoir that maintains functional copies of the viral genome. To this end, several DNA viruses maintain their genomes as extrachromosomal DNA minichromosomes in actively dividing cells. These viruses typically encode a viral protein that binds specifically to viral DNA genomes and tethers them to host mitotic chromosomes, thus enabling the viral genomes to hitchhike or piggyback into daughter cells. Viruses that use this tethering mechanism include papillomaviruses and the gammaherpesviruses Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus. This review describes the advantages and consequences of persistent extrachromosomal viral genome replication.

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McCartney, Sharon L., Bradley S. Taylor et Alina Nicoara. « Functional Tricuspid Regurgitation in Mitral Valve Disease ». Seminars in Cardiothoracic and Vascular Anesthesia 23, n^o 1 (1 novembre 2018) : 108–22. http://dx.doi.org/10.1177/1089253218807922.

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Functional tricuspid regurgitation is a common finding in patients with left-sided heart disease. If left untreated, it may reduce survival, limit functional capacity and cause end-organ dysfunction. Annulus dilation and leaflet tethering due to right ventricle remodeling are 2 major pathophysiologic mechanisms in functional tricuspid regurgitation. Even if surgical treatment remains the gold standard, indication and timing of surgical interventions remain the object of debate in the medical community. More recently, numerous transcatheter therapies have been developed in order to offer less invasive options to patients who otherwise would have a high risk of mortality and morbidity with surgical interventions.

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Wang, Li, Alexey J. Merz, Kevin M. Collins et William Wickner. « Hierarchy of protein assembly at the vertex ring domain for yeast vacuole docking and fusion ». Journal of Cell Biology 160, n^o 3 (3 février 2003) : 365–74. http://dx.doi.org/10.1083/jcb.200209095.

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Vacuole tethering, docking, and fusion proteins assemble into a “vertex ring” around the apposed membranes of tethered vacuoles before catalyzing fusion. Inhibitors of the fusion reaction selectively interrupt protein assembly into the vertex ring, establishing a causal assembly hierarchy: (a) The Rab GTPase Ypt7p mediates vacuole tethering and forms the initial vertex ring, independent of t-SNAREs or actin; (b) F-actin disassembly and GTP-bound Ypt7p direct the localization of other fusion factors; (c) The t-SNAREs Vam3p and Vam7p regulate each other's vertex enrichment, but do not affect Ypt7p localization. The v-SNARE Vti1p is enriched at vertices by a distinct pathway that is independent of the t-SNAREs, whereas both t-SNAREs will localize to vertices when trans-pairing of SNAREs is blocked. Thus, trans-SNARE pairing is not required for SNARE vertex enrichment; and (d) The t-SNAREs regulate the vertex enrichment of both G-actin and the Ypt7p effector complex for homotypic fusion and vacuole protein sorting (HOPS). In accord with this hierarchy concept, the HOPS complex, at the end of the vertex assembly hierarchy, is most enriched at those vertices with abundant Ypt7p, which is at the start of the hierarchy. Our findings provide a unique view of the functional relationships between GTPases, SNAREs, and actin in membrane fusion.

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Farjami, Elaheh, Rui Campos et Elena E. Ferapontova. « Effect of the DNA End of Tethering to Electrodes on Electron Transfer in Methylene Blue-Labeled DNA Duplexes ». Langmuir 28, n^o 46 (7 novembre 2012) : 16218–26. http://dx.doi.org/10.1021/la3032336.

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Tsuboi, Tatsuhisa, et Toshifumi Inada. « Tethering of Poly(A)-binding Protein Interferes with Non-translated mRNA Decay from the 5′ End in Yeast ». Journal of Biological Chemistry 285, n^o 44 (23 août 2010) : 33589–601. http://dx.doi.org/10.1074/jbc.m110.117150.

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Frock, Richard L., Cheyenne Sadeghi, Jodie Meng et Jing L. Wang. « DNA End Joining : G0-ing to the Core ». Biomolecules 11, n^o 10 (9 octobre 2021) : 1487. http://dx.doi.org/10.3390/biom11101487.

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Humans have evolved a series of DNA double-strand break (DSB) repair pathways to efficiently and accurately rejoin nascently formed pairs of double-stranded DNA ends (DSEs). In G0/G1-phase cells, non-homologous end joining (NHEJ) and alternative end joining (A-EJ) operate to support covalent rejoining of DSEs. While NHEJ is predominantly utilized and collaborates extensively with the DNA damage response (DDR) to support pairing of DSEs, much less is known about A-EJ collaboration with DDR factors when NHEJ is absent. Non-cycling lymphocyte progenitor cells use NHEJ to complete V(D)J recombination of antigen receptor genes, initiated by the RAG1/2 endonuclease which holds its pair of targeted DSBs in a synapse until each specified pair of DSEs is handed off to the NHEJ DSB sensor complex, Ku. Similar to designer endonuclease DSBs, the absence of Ku allows for A-EJ to access RAG1/2 DSEs but with random pairing to complete their repair. Here, we describe recent insights into the major phases of DSB end joining, with an emphasis on synapsis and tethering mechanisms, and bring together new and old concepts of NHEJ vs. A-EJ and on RAG2-mediated repair pathway choice.

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Utsunomiya, Hiroto, Yu Harada, Hitoshi Susawa, Yusuke Ueda, Kanako Izumi, Kiho Itakura, Takayuki Hidaka, Takahiro Shiota, Yukiko Nakano et Yasuki Kihara. « Tricuspid valve geometry and right heart remodelling : insights into the mechanism of atrial functional tricuspid regurgitation ». European Heart Journal - Cardiovascular Imaging 21, n^o 10 (5 août 2020) : 1068–78. http://dx.doi.org/10.1093/ehjci/jeaa194.

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Abstract Aims We sought to investigate tricuspid valve (TV) geometry and right heart remodelling in atrial functional tricuspid regurgitation (AF-TR) as compared with ventricular functional TR with sinus rhythm (VF-TR). Methods and results Transoesophageal 3D echocardiography datasets of the TV and right ventricle were acquired in 51 symptomatic patients with severe TR (AF-TR, n = 23; VF-TR, n = 28). Three-dimensional right ventricular (RV) endocardial surfaces were reconstructed throughout the cardiac cycle and then postprocessed using semiautomated integration and segmentation software to calculate position of papillary muscle (PM) tips. Compared with VF-TR, AF-TR had more dilated and posteriorly displaced annulus and less leaflet tethering angles with more prominent right atrium and smaller RV end-systolic volume. On the XY (annular) plane, the centre of annulus was getting closer towards the anterior and posterior PM tips and was going away from the medial PM tip caused by prominent annular dilatation in AF-TR. On the Z-axis, the position of each PM tip in AF-TR was not so much displaced apically as that in VF-TR. Multiple linear regression analyses revealed that right atrial volume and right atrial/RV end-systolic volume ratio were determinants of annular area and orientation in AF-TR, respectively (both P < 0.001). Additionally, the posteromedial-directed component of posterior PM tip position and the apically directed component of the position of all three PM tips were independently associated with TV tethering angles of each leaflet in AF-TR (all P < 0.02). Conclusion Right heart remodelling and its association with 3D TV geometry differ entirely between AF-TR and VF-TR, which may offer distinctive therapeutic implication.

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Yoneguchi, Yuki, Hiroaki Kikuchi, Shintaro Nakagawa, Hironori Marubayashi, Takashi Ishizone, Shuichi Nojima et Kazuo Yamaguchi. « Combined effects of confinement size and chain-end tethering on the crystallization of poly(ε-caprolactone) chains in nanolamellae ». Polymer 160 (janvier 2019) : 73–81. http://dx.doi.org/10.1016/j.polymer.2018.11.030.

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Bai, Rui, Ruixue Wan, Chuangye Yan, Qi Jia, Jianlin Lei et Yigong Shi. « Mechanism of spliceosome remodeling by the ATPase/helicase Prp2 and its coactivator Spp2 ». Science 371, n^o 6525 (26 novembre 2020) : eabe8863. http://dx.doi.org/10.1126/science.abe8863.

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Spliceosome remodeling, executed by conserved adenosine triphosphatase (ATPase)/helicases including Prp2, enables precursor messenger RNA (pre-mRNA) splicing. However, the structural basis for the function of the ATPase/helicases remains poorly understood. Here, we report atomic structures of Prp2 in isolation, Prp2 complexed with its coactivator Spp2, and Prp2-loaded activated spliceosome and the results of structure-guided biochemical analysis. Prp2 weakly associates with the spliceosome and cannot function without Spp2, which stably associates with Prp2 and anchors on the spliceosome, thus tethering Prp2 to the activated spliceosome and allowing Prp2 to function. Pre-mRNA is loaded into a featured channel between the N and C halves of Prp2, where Leu536 from the N half and Arg844 from the C half prevent backward sliding of pre-mRNA toward its 5′-end. Adenosine 5′-triphosphate binding and hydrolysis trigger interdomain movement in Prp2, which drives unidirectional stepwise translocation of pre-mRNA toward its 3′-end. These conserved mechanisms explain the coupling of spliceosome remodeling to pre-mRNA splicing.

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Aversano, T., et P. N. Marino. « Effect of ischemic zone size on nonischemic zone function ». American Journal of Physiology-Heart and Circulatory Physiology 258, n^o 6 (1 juin 1990) : H1786—H1795. http://dx.doi.org/10.1152/ajpheart.1990.258.6.h1786.

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To study the influence of ischemic zone size on function in nonischemic regions, wall thickening and the end-systolic pressure-thickness (ESPTR) relationship were measured before and during a 90-s coronary occlusion, which produced either a small or large (24 or 35% of left ventricular mass) area of ischemia. With both size ischemic areas, nonischemic zone isovolumic and ejection phase wall thickening increased during occlusion, primarily because of increased preload and, to a lesser extent, a reduced pressure component of afterload. The nonischemic region ESPTR was unchanged from preocclusion control with small ischemic mass. With larger ischemic mass, the nonischemic region ESPTR was shifted downward and to the left, indicating reduced end-systolic performance. The decline in the nonischemic zone ESPTR with large ischemic zone size was not due to reduced blood flow, shortening deactivation, reflex effects, or "tethering" but rather to the associated decline in coronary perfusion pressure. Thus the increase of nonischemic region wall thickening during acute ischemia is due to a change in ventricular loading conditions and not augmentation of contractile performance. Larger ischemic zone size can impair function in nonischemic myocardium by reducing the erectile component of end-systolic performance.

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Farjami, Elaheh, Rui Campos et Elena E. Ferapontova. « Correction to “Effect of the DNA End of Tethering to Electrodes on Electron Transfer in Methylene Blue-Labeled DNA Duplexes” ». Langmuir 32, n^o 3 (12 janvier 2016) : 928. http://dx.doi.org/10.1021/acs.langmuir.5b03487.

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Iyengar, Revathi, Maria Faure-Betancourt, Saleh Talukdar, Jinting Ye et Abel Navarro. « Optimizing Spacer Length for Positioning Functional Groups in Bio-Waste ». Environments 5, n^o 9 (2 septembre 2018) : 100. http://dx.doi.org/10.3390/environments5090100.

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The goal of this study was to determine the optimal chain length needed for tethering functional groups on bio-wastes. The purpose of modifying the surface of bio-waste is to improve their affinity for phenols. To this end, four different aminated green tea leaves, with the amine group located at the end of 6, 8, 10, and 12 carbons were synthesized. Green approaches to functionalization lead to fewer reactive sites. Optimizing spacer length is one way to ameliorate this. The aminated tea leaves were prepared by a tosylation reaction followed by displacement with a diamine used in excess. The tea leaves with the amine at the end of six carbons proved to have the best ability to remove 2-chlorophenol (2-CP) from its aqueous solution. It was at least 3–4 times better than native spent tea leaves. The mechanism by which the phenol was removed proved to be primarily an acid–base reaction followed by H-bonding and dipole–dipole interactions. Because of the acid–base interactions, the relatively low-boiling 2-CP did not volatilize off the aminated tea leaves enabling recycling. On the other hand, with activated charcoal, the adsorbed 2-CP volatilized almost completely under ambient conditions.

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Ferrari, Matteo, Diego Dibitetto, Giuseppe De Gregorio, Vinay V. Eapen, Chetan C. Rawal, Federico Lazzaro, Michael Tsabar, Federica Marini, James E. Haber et Achille Pellicioli. « Functional Interplay between the 53BP1-Ortholog Rad9 and the Mre11 Complex Regulates Resection, End-Tethering and Repair of a Double-Strand Break ». PLoS Genetics 11, n^o 1 (8 janvier 2015) : e1004928. http://dx.doi.org/10.1371/journal.pgen.1004928.

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Matveevsky, Sergey, Oxana Kolomiets, Aleksey Bogdanov, Elena Alpeeva et Irina Bakloushinskaya. « Meiotic Chromosome Contacts as a Plausible Prelude for Robertsonian Translocations ». Genes 11, n^o 4 (2 avril 2020) : 386. http://dx.doi.org/10.3390/genes11040386.

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Robertsonian translocations are common chromosomal alterations. Chromosome variability affects human health and natural evolution. Despite the significance of such mutations, no mechanisms explaining the emergence of such translocations have yet been demonstrated. Several models have explored possible changes in interphase nuclei. Evidence for non-homologous chromosomes end joining in meiosis is scarce, and is often limited to uncovering mechanisms in damaged cells only. This study presents a primarily qualitative analysis of contacts of non-homologous chromosomes by short arms, during meiotic prophase I in the mole vole, Ellobius alaicus, a species with a variable karyotype, due to Robertsonian translocations. Immunocytochemical staining of spermatocytes demonstrated the presence of four contact types for non-homologous chromosomes in meiotic prophase I: (1) proximity, (2) touching, (3) anchoring/tethering, and (4) fusion. Our results suggest distinct mechanisms for chromosomal interactions in meiosis. Thus, we propose to change the translocation mechanism model from ‘contact first’ to ‘contact first in meiosis’.

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Röder, Ira V., Kyeong-Rock Choi, Markus Reischl, Yvonne Petersen, Markus E. Diefenbacher, Manuela Zaccolo, Tullio Pozzan et Rüdiger Rudolf. « Myosin Va cooperates with PKA RIα to mediate maintenance of the endplate in vivo ». Proceedings of the National Academy of Sciences 107, n^o 5 (19 janvier 2010) : 2031–36. http://dx.doi.org/10.1073/pnas.0914087107.

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Myosin V motor proteins facilitate recycling of synaptic receptors, including AMPA and acetylcholine receptors, in central and peripheral synapses, respectively. To shed light on the regulation of receptor recycling, we employed in vivo imaging of mouse neuromuscular synapses. We found that myosin Va cooperates with PKA on the postsynapse to maintain size and integrity of the synapse; this cooperation also regulated the lifetime of acetylcholine receptors. Myosin Va and PKA colocalized in subsynaptic enrichments. These accumulations were crucial for synaptic integrity and proper cAMP signaling, and were dependent on AKAP function, myosin Va, and an intact actin cytoskeleton. The neuropeptide and cAMP agonist, calcitonin-gene related peptide, rescued fragmentation of synapses upon denervation. We hypothesize that neuronal ligands trigger local activation of PKA, which in turn controls synaptic integrity and turnover of receptors. To this end, myosin Va mediates correct positioning of PKA in a postsynaptic microdomain, presumably by tethering PKA to the actin cytoskeleton.

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Lalande, Viviane, Isabelle Villemure, Manuel Vonthron, Stefan Parent et Carl-Éric Aubin. « Cyclically controlled vertebral body tethering for scoliosis : an in vivo verification in a pig model of the pressure exerted on vertebral end plates ». Spine Deformity 8, n^o 1 (24 janvier 2020) : 39–44. http://dx.doi.org/10.1007/s43390-019-00021-3.

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HAZARI, A., et D. ELLIOT. « Treatment of End-Neuromas, Neuromas-in-Continuity and Scarred Nerves of the Digits by Proximal Relocation ». Journal of Hand Surgery 29, n^o 4 (août 2004) : 338–50. http://dx.doi.org/10.1016/j.jhsb.2004.01.005.

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This paper reports the results of treatment by proximal relocation of 104 painful nerves in 57 digits in 48 patients. These included 86 digital nerves and 18 terminal branches of the superficial radial nerve and the dorsal branch of the ulnar nerve. Eighty-three were end-neuromas and 14 were neuromas-in-continuity, of which nine followed nerve repair and five occurred following a closed crush injury. Seven were painful as a result of tethering in scarred tissue. Eighty nerves (77%) required a single relocation and 24 (23%) required more than one operation. Ninety-eight per cent of nerve relocations achieved complete pain relief at the primary site. One patient had mild pain on pressure at the primary site after relocation of two nerves from this site. Over 90% of the nerves had no spontaneous pain, pain on movement or hypersensitivity of the overlying skin at the final site of relocation. However, the incidence of mild or no pain on direct pressure at the site of nerve relocation was lower at 83% as relocated nerves, although traumatized less often at the sites chosen for relocation, can still be painful on direct pressure.

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Jakeway, S. C., et U. J. Krull. « Consideration of end effects of DNA hybridization in selection of fluorescent dyes for development of optical biosensors ». Canadian Journal of Chemistry 77, n^o 12 (5 décembre 1999) : 2083–87. http://dx.doi.org/10.1139/v99-200.

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Intercalating fluorescent dyes are in widespread use to detect the presence of double-stranded DNA. Applications include the development of biosensors that rely on the attachment ("tethering") of a dye molecule by a short hydrocarbon chain to the terminus of a strand of DNA so that dye is continuously available and the biosensor is fully reversible. Double strands of DNA have end effects that limit the stability of hybridization and dye intercalation near the termini of the duplexes. Therefore, the selection of the dye must be based on consideration of spectroscopic properties and also issues associated with tether length and the stoichiometry of the binding of the dye with double- and single-stranded DNA. Ethidium bromide (EB) has been used extensively to detect hybridization of DNA in applications such as electrophoresis, gene chips, and biosensors. A number of dyes with greater quantum efficiency than EB for detection of hybridization have been reported. Furthermore, other practical spectroscopic advantages can be gained in terms of improved S/N by use of dyes that have excitation that is red shifted relative to EB. Pyrilium iodide has been disclosed as an intercalator of high quantum efficiency and long excitation wavelength. This work investigates pyrilium iodide in comparison to EB as a candidate for preparation of a tethered dye for detection of hybridization of DNA 20-mers.Key words: biosensors, DNA, hybridization, fluorescence, end effects.

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Bain, Allison C., David I. Shreiber et David F. Meaney. « Modeling of Microstructural Kinematics During Simple Elongation of Central Nervous System Tissue ». Journal of Biomechanical Engineering 125, n^o 6 (1 décembre 2003) : 798–804. http://dx.doi.org/10.1115/1.1632627.

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Damage to axons and glial cells in the central nervous system (CNS) white matter is a nearly universal feature of traumatic brain injury, yet it is not clear how the tissue mechanical deformations are transferred to the cellular components of the CNS. Defining how cellular deformations relate to the applied tissue deformation field can both highlight cellular populations at risk for mechanical injury, and define the fraction of cells in a specific population that will exhibit damage. In this investigation, microstructurally based models of CNS white matter were developed and tested against measured transformations of the CNS tissue microstructure under simple elongation. Results show that axons in the unstretched optic nerves were significantly wavy or undulated, where the measured axonal path length was greater than the end-to-end distance of the axon. The average undulation parameter—defined as the true axonal length divided by the end-to-end length—was 1.13. In stretched nerves, mean axonal undulations decreased with increasing applied stretch ratio (λ)—the mean undulation values decreased to 1.06 at λ=1.06, 1.04 at λ=1.12, and 1.02 at λ=1.25. A model describing the gradual coupling, or tethering, of the axons to the surrounding glial cells best fit the experimental data. These modeling efforts indicate the fraction of the axonal and glial populations experiencing deformation increases with applied elongation, consistent with the observation that both axonal and glial cell injury increases at higher levels of white matter injury. Ultimately, these results can be used in conjunction with computational simulations of traumatic brain injury to aid in establishing the relative risk of cellular structures in the CNS white matter to mechanical injury.

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Liu, Chenyu, Kai K. Ewert, Emily Wonder, Phillip Kohl, Youli Li, Weihong Qiao et Cyrus R. Safinya. « Reversible Control of Spacing in Charged Lamellar Membrane Hydrogels by Hydrophobically Mediated Tethering with Symmetric and Asymmetric Double-End-Anchored Poly(ethylene glycol)s ». ACS Applied Materials & ; Interfaces 10, n^o 50 (21 novembre 2018) : 44152–62. http://dx.doi.org/10.1021/acsami.8b16456.

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Custódio, Noélia, Maria Vivo, Michael Antoniou et Maria Carmo-Fonseca. « Splicing- and cleavage-independent requirement of RNA polymerase II CTD for mRNA release from the transcription site ». Journal of Cell Biology 179, n^o 2 (15 octobre 2007) : 199–207. http://dx.doi.org/10.1083/jcb.200612109.

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Eukaryotic cells have a surveillance mechanism that identifies aberrantly processed pre-mRNAs and prevents their flow to the cytoplasm by tethering them near the site of transcription. Here we provide evidence that mRNA release from the transcription site requires the heptad repeat structure of the C-terminal domain (CTD) of RNA polymerase II. The mammalian CTD, which is essential for normal co-transcriptional maturation of mRNA precursors, comprises 52 heptad repeats. We show that a truncated CTD containing 31 repeats (heptads 1–23, 36–38, and 48–52) is sufficient to support transcription, splicing, cleavage, and polyadenylation. Yet, the resulting mRNAs are mostly retained in the vicinity of the gene after transcriptional shutoff. The retained mRNAs maintain the ability to recruit components of the exon junction complex and the nuclear exosome subunit Rrp6p, suggesting that binding of these proteins is not sufficient for RNA release. We propose that the missing heptads in the truncated CTD mutant are required for binding of proteins implicated in a final co-transcriptional maturation of spliced and 3′ end cleaved and polyadenylated mRNAs into export-competent ribonucleoprotein particles.

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Otomo, Takanori, Saikat Chowdhury et Gabriel C. Lander. « The Rod-Shaped ATG2A-WIPI4 Complex Tethers Membranes In Vitro ». Contact 1 (janvier 2018) : 251525641881993. http://dx.doi.org/10.1177/2515256418819936.

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The autophagosome precursor membrane, termed the isolation membrane or phagophore, emerges adjacent to a phosphatidylinositol 3-phosphate (PI3P)-enriched transient subdomain of the endoplasmic reticulum called the omegasome, thereafter expanding to engulf cytoplasmic content. Uncovering the molecular events that occur in the vicinity of the omegasome during phagophore biogenesis is imperative for understanding the mechanisms involved in this critical step of the autophagy pathway. We recently characterized the ATG2A-WIPI4 complex, one of the factors that localize to the omegasome and play a critical role in mediating phagophore expansion. Our structural and biochemical studies revealed that ATG2A is a rod-shaped protein with membrane-interacting properties at each end, endowing ATG2A with membrane-tethering capability. Association of the PI3P-binding protein WIPI4 at one of the ATG2A tips enables the ATG2A-WIPI4 complex to specifically tether PI3P-containing membranes to non-PI3P-containing membranes. We proposed models for the ATG2A-WIPI4 complex-mediated membrane associations between the omegasome and surrounding membranes, including the phagophore edge, the endoplasmic reticulum, ATG9 vesicles, and COPII vesicles.

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Wu, Shaowen, et Ekaterina L. Grishchuk. « Structural view of the yeast Dam1 complex, a ring-shaped molecular coupler for the dynamic microtubule end ». Essays in Biochemistry 64, n^o 2 (24 juin 2020) : 359–70. http://dx.doi.org/10.1042/ebc20190079.

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Abstract In a dividing eukaryotic cell, proper chromosome segregation requires the dynamic yet persistent attachment of kinetochores to spindle microtubules. In the budding yeast Saccharomyces cerevisiae, this function is especially crucial because each kinetochore is attached to a single microtubule; consequently, loss of attachment could lead to unrecoverable chromosome loss. The highly specialized heterodecameric Dam1 protein complex achieves this coupling by assembling into a microtubule-encircling ring that glides near the end of the dynamic microtubule to mediate chromosome motion. In recent years, we have learned a great deal about the structural properties of the Dam1 heterodecamer, its mechanism of self-assembly into rings, and its tethering to the kinetochore by the elongated Ndc80 complex. The most remarkable progress has resulted from defining the fine structures of helical bundles within Dam1 heterodecamer. In this review, we critically analyze structural observations collected by diverse approaches with the goal of obtaining a unified view of Dam1 ring architecture. A considerable consistency between different studies supports a coherent model of the circular core of the Dam1 ring. However, there are persistent uncertainties about the composition of ring protrusions and flexible extensions, as well as their roles in mediating ring core assembly and interactions with the Ndc80 complex and microtubule.

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OU-YANG, DAVID, MARK MOLDAVSKY, NOLAN WESSELL, DAINA M. BROOKS, MARIANO TITANTI, ERIKA A. MATHEIS, BRANDON S. BUCKLEN et VIKAS PATEL. « Evaluation of Spinous Process Tethering at the Proximal End of Rigid Constructs : In Vitro Range of Motion and Intradiscal Pressure at Instrumented and Adjacent Levels ». International Journal of Spine Surgery 14, n^o 4 (31 juillet 2020) : 571–79. http://dx.doi.org/10.14444/7076.

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Travis, Sophie M., Kevin DAmico, I.-Mei Yu, Conor McMahon, Safraz Hamid, Gabriel Ramirez-Arellano, Philip D. Jeffrey et Frederick M. Hughson. « Structural basis for the binding of SNAREs to the multisubunit tethering complex Dsl1 ». Journal of Biological Chemistry 295, n^o 30 (14 mai 2020) : 10125–35. http://dx.doi.org/10.1074/jbc.ra120.013654.

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Multisubunit-tethering complexes (MTCs) are large (250 to >750 kDa), conserved macromolecular machines that are essential for soluble N-ethylmaleimide–sensitive factor attachment protein receptor (SNARE)–mediated membrane fusion in all eukaryotes. MTCs are thought to organize membrane trafficking by mediating the initial long-range interaction between a vesicle and its target membrane and promoting the formation of membrane-bridging SNARE complexes. Previously, we reported the structure of the yeast Dsl1 complex, the simplest known MTC, which is essential for coat protein I (COPI) mediated transport from the Golgi to the endoplasmic reticulum (ER). This structure suggests how the Dsl1 complex might tether a vesicle to its target membrane by binding at one end to the COPI coat and at the other to ER-associated SNAREs. Here, we used X-ray crystallography to investigate these Dsl1–SNARE interactions in greater detail. The Dsl1 complex comprises three subunits that together form a two-legged structure with a central hinge. We found that distal regions of each leg bind N-terminal Habc domains of the ER SNAREs Sec20 (a Qb-SNARE) and Use1 (a Qc-SNARE). The observed binding modes appear to anchor the Dsl1 complex to the ER target membrane while simultaneously ensuring that both SNAREs are in open conformations, with their SNARE motifs available for assembly. The proximity of the two SNARE motifs, and therefore their ability to enter the same SNARE complex, will depend on the relative orientation of the two Dsl1 legs. These results underscore the critical roles of SNARE N-terminal domains in mediating interactions with other elements of the vesicle docking and fusion machinery.

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Lowe, Martin, Nicholas K. Gonatas et Graham Warren. « The Mitotic Phosphorylation Cycle of the Cis-Golgi Matrix Protein Gm130 ». Journal of Cell Biology 149, n^o 2 (17 avril 2000) : 341–56. http://dx.doi.org/10.1083/jcb.149.2.341.

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The cis-Golgi matrix protein GM130 is phosphorylated in mitosis on serine 25. Phosphorylation inhibits binding to p115, a vesicle-tethering protein, and has been implicated as an important step in the mitotic Golgi fragmentation process. We have generated an antibody that specifically recognizes GM130 phosphorylated on serine 25, and used this antibody to study the temporal regulation of phosphorylation in vivo. GM130 is phosphorylated in prophase as the Golgi complex starts to break down, and remains phosphorylated during further breakdown and partitioning of the Golgi fragments in metaphase and anaphase. In telophase, GM130 is dephosphorylated as the Golgi fragments start to reassemble. The timing of phosphorylation and dephosphorylation correlates with the dissociation and reassociation of p115 with Golgi membranes. GM130 phosphorylation and p115 dissociation appear specific to mitosis, since they are not induced by several drugs that trigger nonmitotic Golgi fragmentation. The phosphatase responsible for dephosphorylation of mitotic GM130 was identified as PP2A. The active species was identified as heterotrimeric phosphatase containing the Bα regulatory subunit, suggesting a role for this isoform in the reassembly of mitotic Golgi membranes at the end of mitosis.

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Pausch, Jonas, Eva Harmel, Christoph Sinning, Hermann Reichenspurner et Evaldas Girdauskas. « Standardized subannular repair for type IIIb functional mitral regurgitation in a minimally invasive mitral valve surgery setting† ». European Journal of Cardio-Thoracic Surgery 56, n^o 5 (21 avril 2019) : 968–75. http://dx.doi.org/10.1093/ejcts/ezz114.

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Abstract OBJECTIVES Subannular repair techniques in addition to undersized ring annuloplasty have been developed to address high mitral regurgitation (MR) recurrence rates after mitral valve repair in type IIIb MR. We compared the results of annuloplasty with simultaneous standardized subannular repair versus isolated annuloplasty, focusing on the periprocedural outcomes of minimally invasive procedures. METHODS A consecutive series of 108 patients with type IIIb functional MR with severe signs of bileaflet tethering underwent an annuloplasty + subannular repair (group A; n = 60) versus isolated annuloplasty (group B; n = 48). The primary end point of this prospective, parallel cohort study was death or recurrent MR >2, 1 year postoperatively. The secondary end points were survival and clinical outcomes, with special regard for the minimally invasively treated subgroups. RESULTS Duration of surgery, cardiopulmonary bypass time and aortic cross-clamp time were comparable between both study groups. Procedural outcomes as well as echocardiographic outcome parameters were similar and independent of access (fully endoscopic versus full sternotomy). At the 12-month follow-up, death or MR >2 occurred in 3.3% (2/60) of patients in group A vs in 20.8% (10/48) of patients in group B (P = 0.037). The overall mortality rate during the follow-up period was 1.7% (1/60) in group A vs 12.5% (6/48) in group B (P = 0.041). CONCLUSIONS Standardized realignment of papillary muscles is feasible and reproducible via a minimally invasive approach, resulting in excellent periprocedural outcomes, and has a clear potential to significantly decrease MR recurrence and improve 1-year outcomes compared to isolated annuloplasty.

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Collins, Scott P., William Rostain, Chunyu Liao et Chase L. Beisel. « Sequence-independent RNA sensing and DNA targeting by a split domain CRISPR–Cas12a gRNA switch ». Nucleic Acids Research 49, n^o 5 (22 février 2021) : 2985–99. http://dx.doi.org/10.1093/nar/gkab100.

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Abstract CRISPR technologies increasingly require spatiotemporal and dosage control of nuclease activity. One promising strategy involves linking nuclease activity to a cell's transcriptional state by engineering guide RNAs (gRNAs) to function only after complexing with a ‘trigger’ RNA. However, standard gRNA switch designs do not allow independent selection of trigger and guide sequences, limiting gRNA switch application. Here, we demonstrate the modular design of Cas12a gRNA switches that decouples selection of these sequences. The 5′ end of the Cas12a gRNA is fused to two distinct and non-overlapping domains: one base pairs with the gRNA repeat, blocking formation of a hairpin required for Cas12a recognition; the other hybridizes to the RNA trigger, stimulating refolding of the gRNA repeat and subsequent gRNA-dependent Cas12a activity. Using a cell-free transcription-translation system and Escherichia coli, we show that designed gRNA switches can respond to different triggers and target different DNA sequences. Modulating the length and composition of the sensory domain altered gRNA switch performance. Finally, gRNA switches could be designed to sense endogenous RNAs expressed only under specific growth conditions, rendering Cas12a targeting activity dependent on cellular metabolism and stress. Our design framework thus further enables tethering of CRISPR activities to cellular states.

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Dumych, Tetiana, Clarisse Bridot, Sébastien Gouin, Marc Lensink, Solomiya Paryzhak, Sabine Szunerits, Ralf Blossey, Rostyslav Bilyy, Julie Bouckaert et Eva-Maria Krammer. « A Novel Integrated Way for Deciphering the Glycan Code for the FimH Lectin ». Molecules 23, n^o 11 (28 octobre 2018) : 2794. http://dx.doi.org/10.3390/molecules23112794.

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The fimbrial lectin FimH from uro- and enteropathogenic Escherichia coli binds with nanomolar affinity to oligomannose glycans exposing Manα1,3Man dimannosides at their non-reducing end, but only with micromolar affinities to Manα1,2Man dimannosides. These two dimannoses play a significantly distinct role in infection by E. coli. Manα1,2Man has been described early on as shielding the (Manα1,3Man) glycan that is more relevant to strong bacterial adhesion and invasion. We quantified the binding of the two dimannoses (Manα1,2Man and Manα1,3Man to FimH using ELLSA and isothermal microcalorimetry and calculated probabilities of binding modes using molecular dynamics simulations. Our experimentally and computationally determined binding energies confirm a higher affinity of FimH towards the dimannose Manα1,3Man. Manα1,2Man displays a much lower binding enthalpy combined with a high entropic gain. Most remarkably, our molecular dynamics simulations indicate that Manα1,2Man cannot easily take its major conformer from water into the FimH binding site and that FimH is interacting with two very different conformers of Manα1,2Man that occupy 42% and 28% respectively of conformational space. The finding that Manα1,2Man binding to FimH is unstable agrees with the earlier suggestion that E. coli may use the Manα1,2Man epitope for transient tethering along cell surfaces in order to enhance dispersion of the infection.

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