Control of histone ubiquitylation during the cell cycle

项目总结 组蛋白的特定位点泛素化可以决定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动态平衡是必不可少的。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。 在间期，~1-2%的组蛋白H_2B是单一泛素化的(H_2Bub1)，与一些 其中最泛素化的是丰度。H_2Bub1已被证明通过 多种机制。引人注目的是，H2Bub1从中期染色体上消失，并重新积累为 细胞退出有丝分裂，但考虑到最近的报道，这些报道挑战了长期以来认为组蛋白起作用的观点 为了在体内将染色质浓缩成更高级的结构，为什么H_2B泛素化的状态需要 在每个细胞周期中的重置还没有完全被理解。因此，迫切需要阐明原因和原因。 H2Bub1是如何从有丝分裂染色体上剥离的。多种脱泛素酶(DUB)已被证明 催化从H_2Bub1中去除泛素，然而，它们如何合作仍有待观察 相互之间，如果还存在未识别的针对H_2Bub1的DUB，它们调控的基因组位置，以及何时 它们在细胞周期中发挥作用。我们的工作假说假设每个特定于H_2Bub1的Dub靶标 重叠但不同的基因组区域，以确保有丝分裂染色体上H2Bub1的快速清除。至 为了解决这一假设，我们将使用多学科方法，整合经典的生物化学方法 全球范围的测量。更具体地说，我们建议确定针对H2Bub1的关键复制片段，以 阐明他们冗余的程度，描述他们的行动机制，并检查他们是如何 影响整个细胞周期的基因表达。虽然这项工作的目的是揭示组蛋白的目的 在有丝分裂过程中的去泛素化，我们也希望对泛素的基本原理有新的见解- 依赖基因调控，包括时空调控、协同作用和相互作用机制 在双音之间，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的 分裂细胞如何维持转录记忆以确保其忠实繁殖的暗示 对子孙后代的细胞身份，这项研究将产生积极影响，为 了解泛素依赖性疾病，并可能揭示如何最好地制定治疗策略 与这些疾病作斗争。

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.