Protection of Centromeric Cohesion by Bub1 and Sgo1

生物体的遗传稳定性取决于姐妹染色单体是否准确划分为两个子体。 细胞在有丝分裂期间，这反过来需要维持姐妹之间的物理联系(凝聚力) 染色单体直到它们的两极附着在有丝分裂纺锤体上。去除粘附素(蛋白质复合体 维持姐妹染色单体的凝聚力)，然后导致姐妹染色单体分离。在……里面 对于脊椎动物细胞，粘附素的去除分两步进行。在前期，大多数粘附素沿着 染色体臂通过Polo-like Kinase(Plk1)/Aurora B依赖的磷酸化被移除 粘附素。在中期，残留的着丝粒粘附素池被分离酶切割，以允许姐妹 染色单体分离。我的实验室的长期目标是了解 哺乳动物细胞中的染色体分离。在这项提案中，我们将解决一个有趣的谜题 区域：着丝粒粘附素是如何被Plk1/Aurora B在早期阶段的作用屏蔽的？我们有 最近提供的证据表明，纺锤体检查点激酶Bub1靶标和Sgo1 着丝粒蛋白和蛋白磷酸酶2A(PP2A)到着丝粒，在那里它们抵消 Plk1和其他有丝分裂酶对粘附素的磷酸化作用。在具体目标1和2中，我们将进一步 描述Bub1、Sgo1和PP2A合作保护着丝粒凝聚力的机制。在……上面 另一方面，我们的结果也表明Sgo1的作用不依赖于PP2A。事实上，我们已经制作了两部小说 以及过去一年的相关发现。Sgo1直接与一种名为 ILF2-ILF3(白细胞介素2和3)。在体外，Sgo1本身可以与RNA结合。实验是 在目标3和4中计划，以确定这些发现的体内相关性。着丝粒过早丢失 姐妹染色单体凝聚导致染色体错误分离和染色体数目异常 子代细胞(非整倍体)，导致癌症形成和出生缺陷。拟议的研究 将阐明染色体分离的机制，并可能反过来导致更好的理解 以及预防人类癌症和出生缺陷的染色体不稳定性和非整倍体，如唐氏综合症 综合症。

The genetic stability of an organism depends on the accurate partition of sister chromatids into two daughter cells during mitosis, which in turn requires the maintenance of the physical linkage (cohesion) between sister chromatids until their bipolar attachment to the mitotic spindle. Removal of cohesin (theprotein complex that maintains sister chromatid cohesion) from chromosomes then leads to sister chromatid separation. In vertebrate cells, removal of cohesin occurs in two steps. At prophase, most of cohesin along the chromosome arms is removed through Polo-like kinase (Plk1)/Aurora B-dependent phosphorylation of cohesin. At metaphase, the residual centromeric pool of cohesin is cleaved by separase to allow sister chromatid separation. The long-term goal of my lab is to understand the molecular mechanism of chromosome segregation in mammalian cells. In this proposal, we will address an interesting puzzle in this area: how is the centromeric cohesin shielded from the actions of Plk1 /Aurora B in prophase? We have recently provided evidence to suggest that the spindle checkpoint kinase Bub1 targets and the Sgo1 centromeric protein and protein phosphatase 2A (PP2A) to centromeres where they counteract the phosphorylation of cohesin by Plk1and other mitotic kinases. In Specific Aims 1 and 2, we will further delineate the mechanisms by which Bub1, Sgo1, and PP2A collaborate to protect centromeric cohesion. On the other hand, our results also point to a PP2A-independent role of Sgo1. Indeed, we have made two novel and related findings in the past year. Sgo1 directly interacts with an RNA-binding protein complex called ILF2-ILF3 (interleukin enhancer binding factors 2 and 3). Sgo1 itself binds to RNA in vitro. Experiments are planned in Aims 3 and 4 to establish the in vivo relevance of these findings. Premature loss of centromeric sister chromatid cohesion leads to chromosome missegregation and abnormal numbers of chromosomes in daughter cells (aneuploidy), which contributes to cancer formation and birth defects. The proposed research will shed light on the mechanism of chromosome segregation and may in turn lead to better understanding and prevention of chromosomal instability and aneuploidy in human cancers and birth defects, such as Down Syndrome.