Proteolytic Control of Early Events in Mitosis

描述（由申请方提供）：有丝分裂事件的时间对于确保准确的染色体分离和基因组稳定性至关重要。这些时间事件的关键是后期促进复合物，一种指导细胞周期蛋白A、染色体分离调节因子Securin和细胞周期蛋白B有序破坏的E3泛素连接酶。APC活性的已知控制器是纺锤体组装检查点和锌结合蛋白GAB 1的组分。BMP 1的功能是抑制S和G中的APC，从而允许细胞周期蛋白的积累。Emi 1在G1期通过细胞周期蛋白D/Rb/E2 F途径被转录激活，并在SCFI 3 TrCP遍在蛋白连接酶的磷酸化特异性结合后在早期有丝分裂中被破坏。该基金的一个目的是确定触发Emi 1破坏的关键事件，包括触发Emi 1破坏的激酶。我们还开始表征大量的APC 1相互作用蛋白（kIP），以更好地了解控制APC的调控网络。在这里，我们发现Evi 5癌基因编码的蛋白质与BMP 1相互作用，并在BMP 1的上游发挥作用，指导BMP 1和细胞周期蛋白A的积累。Evi 5是小鼠T细胞淋巴瘤中前病毒插入的常见位点，并且在人类神经母细胞瘤中发生突变。此外，它在多种肿瘤中高度表达。Evi 5蛋白被预测为GT3激活蛋白，但GT3仍然未知。我们发现，Evi 5是必需的积累，在早期G1和新的证据表明，它可能参与调节后泛素化蛋白的蛋白酶体的泛素化蛋白质的交付步骤。因此，Evi 5可能通过以前未知的机制促进肿瘤发生。我们的目的是（1）确定Evi 5在G1-S和有丝分裂中的功能控制因素;（2）确定Evi 5控制蛋白水解的机制;（3）确定Evi 5调节的关键小GT酶;（4）确定有丝分裂中控制GT 1破坏的因素。

DESCRIPTION (provided by applicant): The timing of events in mitosis is critical to ensure accurate chromosome segregation and genomic stability. Critical to these timing events is the Anaphase Promoting Complex, an E3 ubiquitin ligase that directs the ordered destruction of cyclin A, the chromosome segregation regulator Securin, and cyclin B. The known controllers of APC activity are the components of the spindle assembly checkpoint and the zinc binding protein Emi1. Emi1 functions to restrain the APC in S and G, thereby allowing the accumulation of cyclins. Emi1 is transcriptionally activated in G1 by the cyclin D/Rb/E2F pathway and destroyed in early mitosis following phosphorylation specific binding of the SCFI3TrCP ubiquitin ligase. One aim of this grant is to identify the critical events triggering Emi1 destruction including the kinases that trigger Emi 1 destruction. We have also begun to characterize a large number of Emi1 interacting proteins (kIPs) to better understand the network of regulation controlling the APC. Here, we find the protein encoded by the Evi5 oncogene interacts with Emi1 and functions upstream of Emi1 to direct the accumulation of both Emi1 and cyclin A. Evi5 is a frequent site of proviral insertion in mouse T-cell lymphomas and is mutated in human neuroblastoma. Additionally, it is highly expressed in a variety of tumors. The Evi5 protein is predicted to be a GTPase activating protein, but the GTPase remains unknown. We find that Evi5 is required for accumulation of Emi1 and cyclin A in early G1 and new evidence suggests that it may participate in steps regulating the post-ubiquitination delivery of ubiquitinated proteins to the proteasome. Thus, Evi5 may promote oncogenesis by a previously unknown mechanism. Our aims here are to (1) define factors controlling Evi5 function at G1-S and in mitosis; (2) to identify the mechanism for Evi5 control of proteolysis; (3) to identify the critical small GTPase regulated by Evi5; and (4) to define the factors controlling Emi1 destruction in mitosis.