Mechanisms of Sister Chromatid Pairing

描述(申请人提供)：为了产生可存活的后代，细胞必须将染色体复制的产物鉴定为从S期到染色体分离的姊妹染色单体。姐妹染色单体的一致性是通过复合体的组合来实现的：1)随着时间的推移保持配对的粘连蛋白系链，2)将粘连蛋白加载到姐妹染色单体上的沉积因子，以及3)将染色质相关的粘连蛋白转化为配对或拴系状态的建立因子。所有这些凝聚途径都是必不可少的，因此任何一条途径的突变(维持、沉积和建立)都会导致大量的染色体错误分离和细胞死亡。在凝聚力丧失突变体中观察到的许多表型(非整倍体、基因组不稳定、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丢失的直接后果--所有这些都是癌细胞的特征。更新的发现揭示了凝聚力缺陷和发育异常之间令人惊讶的联系，这些发育异常包括科妮莉亚·德朗格综合征和罗伯茨综合征/SC眼畸形。在分子水平上，文献中第一个建立的模型认为，与每个姐妹相关的粘附素复合体通过与DNA复制叉紧密耦合的活跃过程而连接在一起。几个实验室的发现证实了建立因子(Ctf7/Eco1)和许多DNA复制成分之间的联系，其中包括增殖细胞核抗原、RFC因子和DNA解旋酶。此外，最近的报告提供了重要的线索，关于Ctf7/Eco1乙酰化依赖的粘附素到配对的能力状态的转换，以及早熟转换(配对)是如何被反建立因子阻止的。这个R15区域提案的具体目标是测试新的建立模式，重点是支持和反对建立DNA复制因子在凝聚力乙酰化反应中的作用。此外，我们还测试了有关染色质招募和基本建立因子Ctf7/Eco1激活的模型。) 与公共卫生相关：染色体包含细胞和有机体生长和发育的说明手册。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)中替换细胞，细胞必须复制它们的染色体，然后进行分裂，使每个子细胞获得相同的副本。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.