胞质分裂是细胞周期的最后一步，它把一个细胞在空间上一分为二。这个过程受细胞信号严格调控。有超过100个蛋白和多条信号通道参与了这个过程。然而，如何把这些蛋白和信号组织在一起的机理目前还不清楚。研究表明，脚手架蛋白Anillin是胞质分裂中的一个组织中心。一方面，Anillin与Actin和Myosin II相互作用。另一方面，Anillin与胞质分裂的关键信号蛋白RhoA相互作用。RhoA调控Actin和Myosin II，从而控制收缩环的组装。有趣的是，RhoA反过来受其他Anillin结合蛋白调控：GTP交换因子Ect2和GTP酶激活蛋白RacGAP。Anillin以一种使人疑惑的方式同时与RhoA和它的两个带有相反活性的调控蛋白相互作用，从而调控胞质分裂。在这个项目中，我们将用结构生物学和生物化学的手段，研究Anillin整合RhoA、Ect2和RacGAP相互作用的分子机理。

Cytokinesis physically separates one cell into two during the last step of cell division,which is powered by constriction of the contractile ring at the cleavage furrow. Cytokinesis is a fundamental biological process, and tightly regulated inside the cells. Failure in the control of cytokinesis often leads to chromosomal breakage and generation of polyploidy, resulting in severe human diseases, such as cancer. Over 100 proteins and multiple signaling pathways are involved in cytokinesis. Yet, the molecular machinery of how these proteins and signals are organized together is currently unclear. One of the key organization centers in cytokinesis is the scaffold protein Anillin. On one end, Anillin interacts with Actin and Myosin II, which are the core components of contractile ring. On the other end, Anillin interacts with the essential signaling molecule RhoA, which regulates Actin and Myosin II, and thus the assembly of the contractile ring. The activity of RhoA is in turn controlled by other molecules associated with Anillin. One of them is the GTP exchange factor (GEF) Ect2. Another one is GTPase activation protein (GAP) RacGAP. In a puzzling manner, Anillin organizes the action of RhoA and its two contradictory regulators: Ect2 and RacGAP. In this study, we will use the tools of structural biology, biochemistry and cell biology to dissect the mechanism of how Anillin coordinates the interactions among RhoA, Ect2 and RacGAP.