Cytokinesis and the Cytoskeleton in C. elegans Embryos

描述(申请人提供)：在过去的四年中，我们在特定目标上的进展导致我们发现了一类新的和保守的泛素E3连接酶，它在减数分裂完成后不久以被称为katanin的微管切断复合体的一个亚单位为靶标进行泛素介导的蛋白降解。Katanin是减数分裂所必需的；它的后续降解是有丝分裂纺锤体正确组装所必需的，也是细胞质分裂期间调节皮质微丝收缩能力所必需的。因此，除了影响细胞周期进程的调节外，我们还表明泛素介导的蛋白分解也影响细胞分裂机制本身。重要的是，我们发现的E3连接酶是一类新的基于cullin的E3连接酶的创始成员，由cullin3支架和一个庞大而保守的新接头蛋白家族组成。这一发现极大地扩展了我们对泛素E3靶标特异性的理解，也为E3连接酶的调控提供了新的见解。最后，从对有细胞分裂缺陷的条件突变的广泛筛选中，我们已经鉴定出(I)一个嗜铬细胞激动素和另外三个突变，它们影响中心纺锤体的组装或稳定性，以及细胞质分裂的完成，以及(Ii)大量减数分裂缺陷突变的集合。我们的新目标是通过对这些新突变体的分子遗传学研究来提高我们对细胞质分裂和减数分裂的理解。我们还将继续与瑞士苏黎世ETH的Matthias Peter博士合作，确定影响E3连接酶功能和katanin降解的因素。我们建议研究的过程和基因与重要的人类疾病相关，包括癌症和神经退行性疾病。

DESCRIPTION (provided by applicant): Progress on our specific aims over the past four years has led to our discovery of a novel and conserved class of ubiquitin E3 ligases that targets a subunit of the microtubule-severing complex called katanin for ubiquitin-mediated proteolytic degradation, shortly after the completion of meiosis. Katanin is required for meiosis; its subsequent degradation is required for the proper assembly of mitotic spindles, and for the regulation of cortical microfilament contractility during cytokinesis. Thus in addition to influencing regulators of cell cycle progression, we have shown that ubiquitin-mediated proteolysis also influences the cell division machinery itself. Importantly, the E3 ligase we discovered is the founding member of a new class of Cullin- based E3 ligases, composed of a Cullin3 scaffold and one of a large and conserved family of novel adaptor proteins. This finding greatly extends our understanding of the full range of ubiquitin E3 target specificity, and we also have provided new insights into the regulation of E3 ligases. Finally, from extensive screens for conditional mutants with cell division defects, we have identified (i) a chromokinesin, and three additional mutants, that influence central spindle assembly or stability, and the completion of cytokinesis, and (ii) a large collection of meiosis-defective mutants. Our new aims seek to improve our understanding of cytokinesis and meiosis through a molecular genetic investigation of these new mutants. We also will continue our efforts to identify factors that influence E3 ligase function and katanin degradation, in an ongoing collaboration with Dr. Matthias Peter at the ETH in Zurich, Switzerland. The processes and genes we propose to investigate are relevant to important human diseases, including cancer and neurodegenerative disease.