Mechanisms of Sister Chromatid Pairing

描述（由申请方提供）：为了产生有活力的后代，细胞必须将染色体复制的产物鉴定为S期的姐妹染色单体，直至染色体分离。姐妹染色单体身份是通过以下复合物的组合实现的：1）随时间推移维持配对的粘着蛋白系链，2）将粘着蛋白加载到姐妹染色单体上的沉积因子，以及3）将染色质相关粘着蛋白转化为配对或系链状态的建立因子。所有这些内聚途径都是必不可少的，使得任何一个（维持、沉积和建立）中的突变导致大量染色体错误分离和细胞死亡。在内聚力丧失突变体中观察到的许多表型（非整倍性、基因组不稳定性、DNA修复缺陷、超重组和染色体易位）是早熟姐妹分离和修复模板丧失的直接后果-所有这些都是癌细胞的标志。最近的发现揭示了凝聚力缺陷和发育异常之间的惊人联系，包括科尔内利亚德兰格综合征和罗伯茨综合征/SC短肢畸形。 在分子水平上，文献中提出的第一个建立模型表明，与每个姐妹相关的粘着蛋白复合物通过与DNA复制叉密切偶联的主动过程被拴在一起。来自几个实验室的发现证实了建立因子（Ctf 7/Eco 1）和许多DNA复制成分（包括PCNA，RFC因子和DNA解旋酶）之间的联系。此外，最近的报告提供了重要的线索，Ctf 7/Eco 1乙酰化依赖的转换的cohesins配对主管状态和早熟转换（配对）是如何被阻止的反建立的因素。 这个R15 AREA提案的具体目标是通过关注内聚乙酰化反应中支持和反对建立DNA复制因子的作用来测试建立的新模型。此外，我们测试了关于染色质募集和基本建立因子Ctf 7/Eco 1激活的模型。 公共卫生相关性：染色体包含细胞和生物体生长和发育的指导手册。为了在胚胎发育期间生长，为了应对创伤或在恶劣环境（胃肠道）中更换细胞，细胞必须复制它们的染色体，然后分裂，以便每个子细胞获得相同的拷贝。这项提议探索了关于这些复制的染色体在细胞分裂过程中如何正确分离的新模型。

DESCRIPTION (provided by applicant): To produce viable progeny, cells must identify the products of chromosome replication as sister chromatids from S-phase until chromosome segregation. Sister chromatid identity is achieved by a combination of complexes: 1) cohesin tethers that maintain pairing over time, 2) deposition factors that load cohesins onto sister chromatids and 3) establishment factors that convert chromatin-associated cohesins into a paired or tethered state. All of these cohesion pathways are essential such that mutation in any one (maintenance, deposition and establishment) results in massive chromosome mis-segregation and cell death. Many of the phenotypes observed in cohesion loss mutants (aneuploidy, genome instability, defects in DNA repair, hyper- recombination and chromosomal translocations) are direct consequences of precocious sister separation and loss of a repair template - all hallmarks of cancer cells. More recent findings reveal a surprising link between cohesion defects and developmental abnormalities that include Cornelia de Lange Syndrome and Roberts Syndrome/SC Phocomelia. At the molecular level, the first establishment model posited in the literature suggested that cohesin complexes associated with each sister become tethered together through an active process that is intimately coupled to the DNA replication fork. Findings from several labs confirm the link between the establishment factor (Ctf7/Eco1) and numerous DNA replication components that include PCNA, RFC factors, and DNA helicases. Moreover, recent reports provide important clues regarding Ctf7/Eco1 acetylation-dependent conversion of cohesins to a pairing competent state and how precocious conversion (pairing) is blocked by anti-establishment factors. The Specific Aims of this R15 AREA proposal test new models of establishment by focusing on the role of both pro- and anti- establishment DNA replication factors in cohesion acetylation reactions. In addition, we test models regarding chromatin recruitment and activation of the essential establishment factor Ctf7/Eco1.) PUBLIC HEALTH RELEVANCE: Chromosomes contain the instruction manual for cells and organisms to grow and develop. For growth during embryonic development, in response to trauma or to replace cells in a harsh environment (gastro-intestinal tracts), cells must replicate their chromosomes and then divide such that each daughter cell gets an identical copy. This proposal explores new models regarding how these replicated chromosomes are properly segregated during cell division.