Mob1 Localization and Function During Mitosis

在细胞分裂过程中维持染色体倍性需要染色体的精确协调 分离和胞质分裂，使得收缩环不会在所有复制姐妹之前组装 染色单体正确地附着在有丝分裂纺锤体上，纺锤体组装检查点得到满足。在……里面 发芽和分裂的酵母，这个过程是由一个称为有丝分裂出口的信号级联来促进的 协调有丝分裂退出和胞质分裂的网络/间隔起始网络位于纺锤体极 在启动肌动蛋白环的收缩中起着积极的作用。到目前为止，很少有功能同系物 在动物细胞中具有特征，但在末端组件(Mob1和Dbf2/Sid2)的情况下，有 在两个基因家族中都有扩增。虽然肿瘤抑制功能被归因于 哺乳动物和果蝇的Mob1和Dbf2/Sid2的同源基因在G1/S期间，人们对这些基因是如何表达的知之甚少 分子参与动物细胞的有丝分裂和胞质分裂。培养细胞中Mob1亚型的初步研究 人类细胞表明，定位动力学反映了在酵母中观察到的情况，Mob1在 有丝分裂早期的动点和纺锤体极，胞质分裂的纺锤体中区和中体。 此外，我们已经确定Mob1和染色体乘客复合体相互依赖于 在有丝分裂早期，彼此的动粒定位。最后，我们鉴定了大肿瘤抑制因子2(Lats2)是一种 Mob1a特异性结合蛋白和Dbf2/Sid2激酶可能的功能同源物。使用这些初步的 作为研究的基础，这一应用程序寻求结合分子、生化和活细胞分析来测试 Mob1蛋白在维持染色体倍性方面起调节作用的假说 有丝分裂和间期。形成具体目标的实验路线将：1)确定 Mob1定位于着丝粒的分子决定因素；2)剖析Mob1如何影响极光B 以及3)评估Mob1在Lats2-P53反应中的参与 细胞骨架破坏。这些研究将对动物细胞中出现的一个基因家族提供新的见解 作为细胞增殖的负调节因子(其功能丧失与肿瘤有关 形成)，但在酵母中完成细胞分裂是必不可少的。预计这些研究将有助于我们 协调Mob1如何能够参与CELL的这两个非常不同但绝对关键的功能 周期调节。

Maintenance of chromosomal ploidy during cell division requires a precise coordination of chromosome segregation and cytokinesis such that the contractile ring does not assemble before all replicated sister chromatids are correctly attached to the mitotic spindle and the spindle assembly checkpoint is satisfied. In budding and fission yeast, this process is facilitated by a signaling cascade termed the Mitotic Exit Network/Septation Initiation Network that coordinates mitotic exit and cytokinesis, is based at the spindle pole bodies, and plays an active role in initiating constriction of the actin ring. To date, few functional homologues have been characterized in animal cells, but in the case of the terminal components (Mob1 and Dbf2/Sid2), there have been expansions in both gene families. And while tumor suppressor functions have been ascribed to the mammalian and Drosophila orthologs of Mob1 and Dbf2/Sid2 during G1/S, little is known about how these molecules participate in mitosis and cytokinesis in animal cells. Preliminary studies of Mob1 isoforms in cultured human cells indicate that the localization dynamics mirror that observed in yeast, with Mob1 enriched at the kinetochores and spindle poles early in mitosis, and the spindle midzone and midbody during cytokinesis. Moreover, we have determined that Mob1 and the chromosomal passenger complex are mutually dependent on each other kinetochore localization early in mitosis. Lastly, we identified Large Tumor Supressor 2 (Lats2) as a Mob1A-specific binding protein and possible functional homolog of the Dbf2/Sid2 kinase. Using these preliminary studies as a foundation, this application seeks to combine molecular, biochemical and live cell analyses to test the hypothesis that Mob1 proteins perform roles in regulating in maintaining chromosomal ploidy during both mitosis and interphase. The lines of experimentation that form the Specific Aims will: 1) Determine the molecular determinants of Mob1 localization to the kinetochore; 2) Dissect how Mob1 affects Aurora B function at the kinetochore; and 3) Assess the involvement of Mob1 in the Lats2-p53 response to cytoskeletal disruption. These studies will shed novel insights into a gene family that in animal cells appears to act as a negative regulator of cell proliferation (and whose loss of function is associated with tumor formation), yet is essential for completing cell division in yeast. It is anticipated that these studies will help us reconcile how Mob1 is capable of participating in both of these very different but absolutely critical features of cell cycle regulation.