Histone chaperones and epigenetic silencing

组蛋白伴侣和表观遗传沉默

• 批准号: 8526470
• 负责人: Zhiguo Zhang
• 金额: $ 29.22万
• 依托单位: MAYO CLINIC ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-20 至 2015-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8526470
• 关键词: Address; Aging; Aging-Related Process; Animal Model; Binding; Boxing; Cells; Chromatin; Chromatin Modeling; Chromatin Structure; Complex; Coupled; DNA; DNA biosynthesis; DNA replication fork; Defect; Deposition; Development; Dimerization; Epigenetic Process; Eukaryotic Cell; Exhibits; F Box Domain; Foxes; Gene Expression; Genes; Genetic; Genetic Screening; Genetic Transcription; Genome; Genome Stability; Genomic Instability; Goals; Grant; Heterochromatin; Higher Order Chromatin Structure; Histone H3; Histones; Human; In Vitro; Inherited; Laboratories; Link; Lysine; Maintenance; Malignant Neoplasms; Mammalian Cell; Molecular; Molecular Chaperones; Mutation; Nucleosomes; Play; Process; Proteins; RNA; Recruitment Activity; Regulation; Role; S Phase; Saccharomyces cerevisiae; Saccharomycetales; Surface; Testing; Yeasts; cancer cell; carcinogenesis; dimer; insight; novel; prevent; protein function; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): In eukaryotic cells, DNA is packaged into chromatin that governs gene expression and genome integrity. In order for DNA replication machinery to access DNA, chromatin structure in front of replication forks must temporarily be disassembled. Following DNA replication, parental and newly synthesized histones are deposited onto DNA strands to form nucleosomes, the basic unit of chromatin, and then higher order chromatin structures. This DNA replication-coupled nucleosome assembly process plays an important role in maintenance of genome stability and inheritance of chromatin structures including heterochromatin. Uncoupling of DNA synthesis and chromatin assembly results in genome instability, one of the hallmarks of cancer cells. Moreover, several factors involved in this process have been linked to carcinogenesis and aging. Therefore, it is important to understand how the DNA replication-coupled nucleosome assembly is regulated and how this regulation contributes to transcriptional silencing. Histone chaperones CAF-1, Asf1 and Rtt106 function together to promote nucleosome assembly during S phase of the cell cycle. These factors are also required for transcriptional silencing in budding yeast. Genetic studies indicate that the role of Asf1 and Rtt106 in transcriptional silencing is linked to their ability to bind histones and thereby promote nucleosome assembly. However, it is not known how Rtt106 is recruited to DNA replication forks to promote nucleosome formation during S phase of the cell cycle. Moreover, how histone (H3-H4)2 tetramers are formed through the action of Asf1 remains elusive because Asf1 binds to histone H3 through the same surface involved in (H3-H4)2 tetramer formation. Lastly, through a genetic screen, we have found that Dia2, an F-box containing protein and a component of the SCF E3 ubiquitin ligase, functions in parallel with Rtt106 in transcriptional silencing. However, it is not known how Dia2 impacts transcriptional silencing. In this proposal, we will determine how Rtt106 is recruited to replicating DNA to promote nucleosome assembly; determine the molecular mechanisms by which (H3-H4)2 tetramers are formed from H3-H4 dimers in the Asf1-H3- H4 complex; and elucidate the Dia2's role in transcriptional silencing. These studies will provide novel insight into the molecular mechanism of DNA replication-coupled nucleosome assembly, an important but poorly understood process, that when gone awry, contributes to the development of cancer and aging in humans.

描述（由申请人提供）：在真核细胞中，将DNA包装到控制基因表达和基因组完整性的染色质中。为了使DNA复制机制访问DNA，必须暂时拆卸复制叉前的染色质结构。 DNA复制后，将亲本和新合成的组蛋白沉积到DNA链上，形成核小体，染色质的基本单位，然后形成高阶染色质结构。该DNA复制耦合核小体组装过程在维持基因组稳定性和包括异染色质在内的染色质结构的遗传性中起着重要作用。 DNA合成和染色质组装的解偶联导致基因组不稳定性，这是癌细胞的标志之一。此外，此过程中涉及的几个因素与癌变和衰老有关。因此，重要的是要了解如何调节DNA复制耦合的核小体组装以及该调节如何有助于转录沉默。组蛋白伴侣CAF-1，ASF1和RTT106在细胞周期的S相期间共同促进核小体组装。这些因素也是萌芽酵母中的转录沉默所必需的。遗传研究表明，ASF1和RTT106在转录沉默中的作用与它们结合组蛋白的能力有关，从而促进核小体组装。然而，尚不清楚如何募集RTT106在DNA复制叉中以促进细胞周期阶段的核小体形成。此外，如何通过ASF1的作用形成组蛋白（H3-H4）2四聚体仍然难以捉摸，因为ASF1通过（H3-H4）2四聚体形成与组蛋白H3结合。最后，通过遗传筛选，我们发现DIA2是一个含有蛋白质的F-box和SCF E3泛素连接酶的成分，与转录沉默中的RTT106并行起作用。但是，尚不清楚DIA2如何影响转录沉默。在此提案中，我们将确定如何募集RTT106来复制DNA以促进核小体组装；确定（H3-H4）2四聚体由ASF1-H3-H4复合物中的H3-H4二聚体形成的分子机制；并阐明了DIA2在转录沉默中的作用。这些研究将为DNA复制耦合核小体组装的分子机制提供新的见解，这是一个重要但知之甚少的过程，即出现问题时，会导致人类癌症和衰老的发展。