Control of histone ubiquitylation during the cell cycle

项目摘要 组蛋白的位点特异性泛素化可以决定一个基因是表达还是沉默，因此， 这种类型的修饰对于正常发育和细胞内稳态是必不可少的。相比之下， 组蛋白泛素化的错误调节可导致发育致死、神经变性和衰老。 ~1-2%的组蛋白H2 B在间期被单泛素化（H2 Bub 1），将该蛋白与一些 是最普遍化的。H2 Bub 1已被证明通过以下途径促进基因表达： 多重机制引人注目的是，H2 Bub 1从中期染色体上消失，并在细胞分裂时重新积累。 细胞退出有丝分裂，但考虑到最近的报告，这挑战了长期持有的观点，即组蛋白的功能 为了在体内将染色质浓缩成更高级的结构，为什么H2 B泛素化的状态需要 在每个细胞周期期间的重置不完全理解。因此，迫切需要阐明为什么， H2 Bub 1是如何从有丝分裂染色体上剥离的。多种去泛素化酶（DUB）已被证明 催化从H2 Bub 1中去除泛素，然而，它们如何与H2 Bub 1合作还有待观察。 彼此，如果有尚未确定的DUB特异性H2 Bub 1，基因组位点，他们调节，当 它们在细胞周期中发挥作用。我们的工作假设假定每个H2 Bub 1特异性DUB靶向 重叠但不同的基因组区域，以确保快速清除有丝分裂染色体上的H2 Bub 1。到 为了解决这一假设，我们将采用多学科方法，整合经典的生物化学方法， 全球测量。更具体地说，我们建议识别靶向H2 Bub 1的关键DUB， 阐明其冗余程度，描述其作用机制，并研究它们如何 影响整个细胞周期的基因表达。虽然这项工作旨在揭示组蛋白的作用， 在有丝分裂过程中去泛素化，我们也希望获得新的见解泛素的基本原则， 依赖性基因调控，包括时空控制、协同性和相互作用机制 DUB之间的干扰，以及与其他染色质修饰酶的串扰。最后，我们的工作将有重大意义。 在分裂细胞如何维持其转录记忆，以确保忠实的传播的影响， 细胞身份给后代，这项研究将产生积极的影响，提供一个新的背景下， 了解泛素依赖性疾病，并可能揭示如何最好地开发治疗策略， 对抗这些疾病。

PROJECT SUMMARY The site-specific ubiquitylation of histone proteins can dictate whether a gene gets expressed or silenced, thus, this type of modification is indispensable for normal development and cellular homeostasis. By contrast, the mis-regulation of histone ubiquitylation can result in developmental lethality, neurodegeneration, and aging. ~1–2% of histone H2B is mono-ubiquitylated (H2Bub1) during interphase, ranking this protein alongside some of the most ubiquitylated by abundance. H2Bub1 has been shown to promote gene expression through multiple mechanisms. Strikingly, H2Bub1 disappears from metaphase chromosomes and reaccumulates as cells exit from mitosis, but considering recent reports, which challenge the long-held view that histones function to condense chromatin into higher-order structures in vivo, why the state of H2B ubiquitylation needs to be reset during each cell cycle is incompletely understood. Thus, there is a pressing need to elucidate why and how H2Bub1 is stripped from mitotic chromosomes. Multiple deubiquitylases (DUBs) have been shown to catalyze the removal of ubiquitin from H2Bub1, nonetheless, it remains to be seen how they cooperate with one another, if there are yet unidentified DUBs specific for H2Bub1, the genomic sites they regulate, and when they function during the cell cycle. Our working hypothesis posits that each H2Bub1-specific DUB targets overlapping but distinct genomic regions to ensure the rapid clearance of H2Bub1 on mitotic chromosomes. To address this hypothesis, we will use a multidisciplinary approach, integrating classical biochemical approaches with global measurements. More specifically, we propose to identify the key DUBs that target H2Bub1, to elucidate the extent of their redundancy, to characterize their mechanisms of action, and to examine how they influence gene expression throughout the cell cycle. Though this work aims to uncover the purpose of histone deubiquitylation during mitosis, we also expect to gain new insights into the basic principles of ubiquitin- dependent gene regulation, including mechanisms of spatiotemporal control, cooperativity and interplay between DUBs, and crosstalk with other chromatin-modifying enzymes. Finally, our work will have major implications in how dividing cells maintain their transcriptional memory to ensure the faithful propagation of cellular identity to future generations, and this study will have a positive impact by providing a fresh context for understanding ubiquitin-dependent disorders and may reveal how best to develop therapeutic strategies to combat these diseases.