Regulation of chromosome segregation by SMC complexes and Top2 in S. pombe

粟酒裂殖酵母中 SMC 复合物和 Top2 对染色体分离的调节

• 批准号: 8403401
• 负责人: MATTHEW J O'CONNELL
• 金额: $ 32.59万
• 依托单位: ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8403401
• 关键词: ATP phosphohydrolase; Acetyltransferase; Address; Affect; Aging; Anaphase; Aneuploidy; Biochemical; Biological; Cancer Biology; Cell Cycle; Cell Survival; Cells; Chromosome Arm; Chromosome Condensation; Chromosome Segregation; Chromosome Structures; Chromosomes; Chromosomes, Human, Pair 12; Collection; Complex; DNA; DNA Damage; DNA Repair; DNA Repair Gene; DNA biosynthesis; Data; Defect; Development; Elements; Ensure; Excision; Fission Yeast; Functional disorder; Genes; Genetic; Genome; Genotoxic Stress; Head; Homologous Gene; Human; Interphase; Interphase Chromosome; Investigation; Link; Maintenance; Malignant Neoplasms; Mediating; Mitosis; Mitotic; Mitotic Chromosome; Mutation; Peptide Hydrolases; Phenotype; Physical condensation; Prophase; Protein Family; Proteins; RNA Interference; Radiation; Regulation; Repair Complex; Role; Saccharomyces cerevisiae; Saccharomycetales; Secondary to; Shapes; Sister Chromatid; Staging; Structure; Superhelical DNA; Tail; Topoisomerase II; Work; cohesin; cohesion; condensin; dimer; homologous recombination; member; mutant; prevent; protein complex; public health relevance; repaired; scaffold; segregation; separase; spatiotemporal

DESCRIPTION (provided by applicant): Three multi-protein complexes scaffolded by members of the Structural Maintenance of Chromosomes (SMC) family of protein are key regulators of chromosome dynamics: cohesin (Smc1/3), condensin (Smc2/4) and the Smc5/6 complex. Cohesin is a key determinant of sister chromatid cohesion, where it is proposed to form a ring-shaped structure that encircles sister chromatids. Condensin is critical for mitotic chromosome condensation, at least in part by generating supercoiled DNA. However, there are also data to link cohesin to chromosome condensation, and condensin to sister chromatid cohesion. Further, both complexes are required for DNA repair, which is thought to be a secondary effect of their role in chromosome organization. Moreover, Topoisomerase II (Top2) functions in cohesion and condensation, in addition to its well-defined roles in chromosome decatenation and scaffolding of mitotic chromosomes. Thus, there is much cross talk between these complexes as cells progress through the cell cycle. The third SMC complex, Smc5/6, has been implicated in a late stage of DNA repair by homologous recombination. However, is a role in DNA repair a direct effect, or an indirect consequence of Smc5/6 function in regulating chromosome structure? Its description as a DNA repair complex is primarily historic, as it was first defined by rad18-X (now smc6-X), a radiation sensitive mutant in Schizosaccharomyces pombe. Moreover, the same collection of rad mutants includes the cohesin gene rad21. Further, Smc5/6 is essential for cell viability, but DNA repair genes are not. Thus the central question we wish to address is why is Smc5/6 essential? The data thus far suggest that Smc5/6 function is essential for accurate chromosome segregation. We have previously shown that Smc5/6 mutants show high levels of aneuploidy, and show failed mitoses following DNA damage or Top2 dysfunction. Further, Smc5/6 null mutants have a terminal phenotype of failed mitoses without extrinsic DNA damage. We propose that all three SMC complexes and Top2 functionally interact to guide chromosomes through DNA replication and mitosis. While most studies on Smc5/6 have been in the context of DNA repair, this proposal focuses specifically on the essential role of Smc5/6 in chromosome segregation, and how Smc5/6 functionally interacts with Cohesin and Topoisomerase II to ensure chromosome segregation. To this end, working in S. pombe, we pursue three specific aims that take cell biological, genetic, and biochemical approaches. First, we build on a significant body of preliminary data that links the mitotic defects of smc6 mutants following DNA damage to a defect in pre-anaphase cohesin removal. Here, we address cause versus consequence and the spatiotemporal regulation of cohesin dynamics. Secondly, we address the functional interaction between Smc5/6 and Top2, which we believe is critical for the segregation of undamaged chromosomes. Finally, we address the function of the acetyltransferase Eso1, a cohesin regulator that mechanistically links cohesin and Smc5/6 function.

描述（由申请人提供）：由染色体结构维持（SMC）蛋白家族成员支撑的三种多蛋白复合物是染色体动力学的关键调节因子：黏结蛋白（Smc1/3），凝聚蛋白（Smc2/4）和Smc5/6复合物。内聚蛋白是姐妹染色单体内聚的关键决定因素，它被提出形成环绕姐妹染色单体的环状结构。凝聚蛋白对有丝分裂的染色体凝聚至关重要，至少部分是通过产生超卷曲的DNA。然而，也有数据表明，凝聚蛋白与染色体凝聚有关，凝聚蛋白与姐妹染色单体凝聚有关。此外，这两种复合物都是DNA修复所必需的，这被认为是它们在染色体组织中的次要作用。此外，拓扑异构酶II （Top2）除了在染色体脱链和有丝分裂染色体的支架中有明确的作用外，还具有内聚和凝聚的功能。因此，当细胞在细胞周期中前进时，这些复合物之间有很多的串扰。第三个SMC复合体Smc5/6参与了DNA同源重组修复的后期阶段。然而，在DNA修复中的作用是Smc5/6调节染色体结构的直接影响，还是间接后果？它作为DNA修复复合体的描述主要是历史性的，因为它首先是由rad18-X（现在的smc6-X）定义的，rad18-X是裂糖菌中的一种辐射敏感突变体。此外，同一组rad突变体包括内聚蛋白基因rad21。此外，Smc5/6对细胞活力至关重要，但DNA修复基因却不是。因此，我们希望解决的中心问题是为什么Smc5/6是必不可少的？迄今为止的数据表明Smc5/6的功能对于准确的染色体分离是必不可少的。我们之前已经证明Smc5/6突变体表现出高水平的非整倍性，并且在DNA损伤或Top2功能障碍后表现出有丝分裂失败。此外，Smc5/6零突变体具有无外部DNA损伤的有丝分裂失败的终端表型。我们认为这三种SMC复合体和Top2在功能上相互作用，引导染色体进行DNA复制和有丝分裂。虽然大多数关于Smc5/6的研究都是在DNA修复的背景下进行的，但本研究特别关注Smc5/6在染色体分离中的重要作用，以及Smc5/6如何与内聚蛋白和拓扑异构酶II相互作用以确保染色体分离。为此，在S. pombe工作，我们追求三个特定的目标，采取细胞生物学，遗传学和生化方法。首先，我们建立了一个重要的初步数据体，将DNA损伤后smc6突变体的有丝分裂缺陷与后期前内聚蛋白去除缺陷联系起来。在这里，我们解决的原因与后果和内聚动力学的时空调节。其次，我们研究了Smc5/6和Top2之间的功能相互作用，我们认为这对未受损染色体的分离至关重要。最后，我们讨论了乙酰转移酶Eso1的功能，Eso1是一种内聚蛋白调节因子，它将内聚蛋白和Smc5/6功能机械地联系起来。