ESCRT and MIT Complexes in Cytokinesis

项目摘要/摘要 为了分裂，细胞必须忠实地分割它们复制的基因组(有丝分裂)，然后分离(胞质分裂)。决赛 胞质分裂的脱落步骤是由ESCRT机器催化的，它切断中体以分离新生细胞 子代细胞。这一步骤受到NoCut/脱落检查点的负调控，以响应有丝分裂错误，如 细胞间DNA桥或不完全的核孔形成，为细胞提供纠正错误或安装的时间 保护性反应。因此，NoCut失败会导致DNA损伤，并与几种癌症有关。 在中体内，ESCRT-III蛋白形成膜结合的细丝，与Vps4 ATPase合作收缩 然后切开薄膜。这些细丝也结合了其他MIT结构域的辅助因子，这些辅助因子参与NoCut和 离位。我们以前发现了三类具有重要细胞动力学功能的MIT酶：1)ULK3激酶， 它使ESCRT-III蛋白磷酸化并失活，2)VPS4和相关的减数分裂分支AAA ATPase，以及3) CAPN7半胱氨酸蛋白酶。我们现在将研究后两类MIT酶在细胞质分裂中如何发挥作用 重塑ESCRT-III细丝(VPS4)，切断纺锤体微管(SPASTIN和Katanin)，或维持NoCut信号 然后促进脱落(CAPN7和SPASTIN)。我们最近还发现了一种以前没有特征的 细胞质细胞器，脱落检查点小体(ACB)，对NoCut脱落延迟有贡献，显然是通过 隔离必需的ESCRT分离因子，如Alix，远离中体。我们现在将阐明ACBS是如何 形成并有助于调节离位时机。我们的最终目标是定义细胞如何维护NoCut信号以防止 过早脱落，然后切断中体，产生单独的子细胞。

PROJECT SUMMARY/ABSTRACT To divide, cells must faithfully partition their duplicated genomes (mitosis) and then separate (cytokinesis). The final abscission step of cytokinesis is catalyzed by the ESCRT machinery, which severs the midbody to separate the nascent daughter cells. This step is negatively regulated by the NoCut/abscission checkpoint in response to mitotic errors such as intercellular DNA bridges or incomplete nuclear pore formation, providing cells with time to correct errors or mount protective responses. NoCut failure therefore results in DNA damage and is linked to several types of cancer. Within the midbody, ESCRT-III proteins form membrane-bound filaments that collaborate with VPS4 ATPases to constrict and cut the membrane. These filaments also bind other MIT domain-containing cofactors that participate in NoCut and abscission. We previously identified three classes of MIT enzymes with important cytokinetic functions: 1) ULK3 kinase, which phosphorylates and inactivates ESCRT-III proteins, 2) VPS4s and related “meiotic clade” AAA ATPases, and 3) the CAPN7 cysteine protease. We will now study how the latter two classes of MIT enzymes function during cytokinesis to remodel ESCRT-III filaments (VPS4s), sever spindle microtubules (SPASTIN and KATANIN), or sustain NoCut signaling and then promote abscission (CAPN7 and SPASTIN). We have also recently discovered a previously uncharacterized cytoplasmic organelle, the Abscission Checkpoint Body (ACB), that contributes to NoCut abscission delay, apparently by sequestering essential ESCRT abscission factors like ALIX away from the midbody. We will now elucidate how ACBs form and help to regulate abscission timing. Our ultimate goal is to define how cells maintain NoCut signaling to prevent premature abscission, and then sever the midbody to create separate daughter cells.