Shuster Charles B, Burgess David R
Department of Biology, Boston College, Chestnut Hill, MA 02467, USA.
Curr Biol. 2002 May 14;12(10):854-8. doi: 10.1016/s0960-9822(02)00838-2.
Anaphase, mitotic exit, and cytokinesis proceed in rapid succession, and while mitotic exit is a requirement for cytokinesis in yeast, it may not be a direct requirement for furrow initiation in animal cells. In this report, we physically manipulated the proximity of the mitotic apparatus (MA) to the cell cortex in combination with microinjection of effectors of the spindle checkpoint and CDK1 activity to determine how the initiation of cytokinesis is coupled to the onset of anaphase and mitotic exit. Whereas precocious contact between the MA and the cell surface advanced the onset of cytokinesis into early anaphase A, furrowing could not be advanced prior to the metaphase-anaphase transition. Additionally, while cells arrested in anaphase could be induced to initiate cleavage furrows, cells arrested in metaphase could not. Finally, activation of the mitotic checkpoint in one spindle of a binucleate cell failed to arrest cytokinesis induced by the control spindle but did inhibit the formation of furrows between the arrested MA and the control, nonarrested MA. Our experiments suggest that the competence of the mitotic apparatus to initiate cytokinesis is not dependent on cyclin degradation but does require anaphase-promoting complex (APC) activity and, thus, inactivation of the mitotic checkpoint.
后期、有丝分裂退出和胞质分裂迅速相继发生，虽然在酵母中，有丝分裂退出是胞质分裂的必要条件，但在动物细胞中，它可能不是沟起始的直接必要条件。在本报告中，我们通过物理方式操纵有丝分裂器（MA）与细胞皮层的接近程度，并结合微注射纺锤体检查点效应器和CDK1活性，以确定胞质分裂的起始如何与后期和有丝分裂退出的开始相偶联。虽然MA与细胞表面的过早接触将胞质分裂的开始提前到了后期A早期，但在中期-后期转变之前，沟的形成无法提前。此外，虽然处于后期停滞的细胞可以被诱导开始形成分裂沟，但处于中期停滞的细胞则不能。最后，双核细胞的一个纺锤体中的有丝分裂检查点激活未能阻止由对照纺锤体诱导的胞质分裂，但确实抑制了停滞的MA和对照的、未停滞的MA之间沟的形成。我们的实验表明，有丝分裂器启动胞质分裂的能力不依赖于细胞周期蛋白降解，但确实需要后期促进复合物（APC）的活性，因此需要有丝分裂检查点的失活。
