Guo Zhihao, Batiha Osamah, Bourouh Mohammed, Fifield Eric, Swan Andrew
Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada N9B 2P1.
Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada N9B 2P1
J Cell Sci. 2016 Feb 1;129(3):531-42. doi: 10.1242/jcs.179358. Epub 2015 Dec 16.
Chromosome segregation in meiosis is controlled by a conserved pathway that culminates in Separase-mediated cleavage of the α-kleisin Rec8, leading to dissolution of cohesin rings. Drosophila has no gene encoding Rec8, and the absence of a known Separase target raises the question of whether Separase and its regulator Securin (Pim in Drosophila) are important in Drosophila meiosis. Here, we investigate the role of Securin, Separase and the cohesin complex in female meiosis using fluorescence in situ hybridization against centromeric and arm-specific sequences to monitor cohesion. We show that Securin destruction and Separase activity are required for timely release of arm cohesion in anaphase I and centromere-proximal cohesion in anaphase II. They are also required for release of arm cohesion on polar body chromosomes. Cohesion on polar body chromosomes depends on the cohesin components SMC3 and the mitotic α-kleisin Rad21 (also called Vtd in Drosophila). We provide cytological evidence that SMC3 is required for arm cohesion in female meiosis, whereas Rad21, in agreement with recent findings, is not. We conclude that in Drosophila meiosis, cohesion is regulated by a conserved Securin-Separase pathway that targets a diverged Separase target, possibly within the cohesin complex.
减数分裂中的染色体分离由一条保守途径控制，该途径最终导致Separase介导的α- kleisin Rec8的切割，从而导致黏连蛋白环的解体。果蝇没有编码Rec8的基因，并且缺乏已知的Separase作用靶点，这就引发了一个问题，即Separase及其调节因子Securin（果蝇中的Pim）在果蝇减数分裂中是否重要。在这里，我们使用针对着丝粒和臂特异性序列的荧光原位杂交来监测黏连，研究了Securin、Separase和黏连蛋白复合体在雌性减数分裂中的作用。我们发现，Securin的降解和Separase的活性对于后期I中臂黏连的及时释放以及后期II中着丝粒近端黏连的释放是必需的。它们对于极体染色体上臂黏连的释放也是必需的。极体染色体上的黏连取决于黏连蛋白成分SMC3和有丝分裂α- kleisin Rad21（在果蝇中也称为Vtd）。我们提供了细胞学证据，表明SMC3是雌性减数分裂中臂黏连所必需的，而Rad21，与最近的研究结果一致，并非必需。我们得出结论，在果蝇减数分裂中，黏连由一条保守的Securin - Separase途径调控，该途径作用于一个可能位于黏连蛋白复合体内的不同的Separase作用靶点。
