Proteolytic Regulation of Centrosome Assembly

项目主任/主要研究者（最后，第一，中间）：宋美惠 总结 中心体，作为主要的微管组织中心，建立双极纺锤体，确保精确的 将基因内容传递到两个子细胞中。为了保持基因组的完整性，中心体数目 必须通过每个细胞周期仅复制一次来严格调节。异常中心体与 人类疾病，包括癌症、小头畸形和其他发育缺陷。我们的长期目标是 利用早期C.线虫胚胎 作为体内模型。总体目标是研究泛素连接酶，后期促进 APC/C和辅激活因子FZR-1（人Cdh 1）参与中心体组装 通过中心体因子的蛋白酶体降解。FZR-1/Cdh 1（APC/C辅因子）赋予底物- 通过识别高度保守的降解决定子基序（KEN盒和D盒）结合。Cdh 1缺陷小鼠表现出 胚胎致死性、基因组不稳定性和对肿瘤发生和脑缺陷的更高易感性 发展中心体组分的丰度直接影响中心体数量： 中心体因子的降解引起额外的中心体，而耗尽抑制中心体复制。 虽然我们认识到APC/C复合物对调节中心体因子水平的巨大影响，但其底物 库和调节机制仍然难以捉摸。我们建议研究SAS-7作为潜在的底物 结果表明，SAS-7在APC/CFZR-1中的作用是在中心体组装的最上游，SAS-7蛋白含有保守的 多个位点的降解决定子基序。我们假设SAS-7是另一个中心体因子， 针对APC/CFZR-1。抑制APC/CFZR-1阻断SAS-7降解，导致SAS-7的超稳定 并补偿zyg-1突变体中ZYG-1功能的部分丧失。我们的理论是， 研究APC/CFZR-1在中心体组装中的作用将有助于揭示其调控机制 APC/CFZR-1是细胞分裂保真度所必需的。该项目的目的是（1）确定SAS-7水平是否 受APC/CFZR-1依赖性蛋白水解的影响，（2）鉴定SAS-7内的功能性降解决定子基序，介导 APC/CFZR-1靶向，以及（3）了解APC/CFZR-1依赖的SAS-7蛋白水解调节 有助于中心体的组装和功能。在模型系统C中使用基于体内的遗传学。 elegans将为理解人类系统奠定基础。拟议项目应有助于 人类中心体生物学的基本理解和治疗干预的进展 人类疾病和病症，如癌症和与异常中心体相关的小头畸形。

Program Director/Principal Investigator (Last, First, Middle): Song, Mi Hye Summary Centrosomes, as the primary microtubule-organizing center, establish bipolar spindles that ensure accurate transmission of genetic contents into two daughter cells. To maintain genomic integrity, centrosome number must be strictly regulated by duplicating only once per cell cycle. Abnormal centrosomes are associated with human disorders, including cancers, microcephaly and other developmental defects. Our long-term goal is to understand the genetic mechanisms of centrosome function and assembly using the early C. elegans embryo as an in vivo model. The overall objective is to investigate how the ubiquitin ligase, anaphase promoting complex/cyclosome (APC/C) and the coactivator FZR-1 (Cdh1 in human), contributes to centrosome assembly through proteasomal degradation of centrosome factors. FZR-1/Cdh1 (an APC/C cofactor) confers a substrate- binding through recognizing highly conserved degron motifs (KEN- and D-boxes). Cdh1-deficient mice exhibit embryonic lethality, genomic instability, and higher susceptibility to tumorigenesis and defective brain development. The abundance of centrosome components directly influences centrosome number: Blocking degradation of centrosome factors causes extra centrosomes, while depletion inhibits centrosome duplication. While we realize the great impact of the APC/C complex for regulating levels of centrosome factors, its substrate repertoire and regulatory mechanisms remain elusive. We propose to investigate SAS-7 as a potential substrate of APC/CFZR-1: SAS-7 functions most upstream in centrosome assembly and SAS-7 protein contains conserved degron motifs at multiple sites. We hypothesize that SAS-7 is another centrosome factor that is directly targeted APC/CFZR-1. Inhibiting APC/CFZR-1 blocks SAS-7 degradation, leading to hyper-stabilization of SAS-7 and compensating for a partial loss of ZYG-1 function in zyg-1 mutants. Our rationale is that its substrate repertoire of APC/CFZR-1 in centrosome assembly and defining their role will reveal the regulatory mechanisms of APC/CFZR-1 required for the fidelity of cell division. The aims of the project are to (1) determine if SAS-7 levels are affected by APC/CFZR-1-dependent proteolysis, (2) identify functional degron motifs within SAS-7, mediating APC/CFZR-1 targeting, and (3) understand how APC/CFZR-1-dependent proteolytic regulation of SAS-7 contributes to centrosome assembly and function. The use of in vivo-based genetics in a model system C. elegans will lay the groundwork for understanding human systems. The proposed project should contribute to advances in fundamental understandings of centrosome biology in humans and therapeutic interventions for human diseases and conditions such as cancers and microcephaly associated with abnormal centrosomes.