Hamant Olivier, Golubovskaya Inna, Meeley Robert, Fiume Elisa, Timofejeva Ljuda, Schleiffer Alexander, Nasmyth Kim, Cande W Zacheus
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720, USA.
Curr Biol. 2005 May 24;15(10):948-54. doi: 10.1016/j.cub.2005.04.049.
During meiosis, sequential release of sister chromatid cohesion (SSC) during two successive nuclear divisions allows the production of haploid gametes from diploid progenitor cells. Release of SSC along chromosome arms allows first a reductional segregation of homologs, and, subsequently, release of centromeric cohesion at anaphase II allows the segregation of chromatids. The Shugoshin (SGO) protein family plays a major role in the protection of centromeric cohesion in Drosophila and yeast. We have isolated a maize mutant that displays premature loss of centromeric cohesion at anaphase I. We showed that this phenotype is due to the absence of ZmSGO1 protein, a maize shugoshin homolog. We also show that ZmSGO1 is localized to the centromeres. The ZmSGO1 protein is not found on mitotic chromosomes and has no obvious mitotic function. On the basis of these results, we propose that ZmSGO1 specifically maintains centromeric cohesion during meiosis I and therefore suggest that SGO1 core functions during meiosis are conserved across kingdoms and in large-genome species. However, in contrast to other Shugoshins, we observed an early and REC8-dependent recruitment of ZmSGO1 in maize, suggesting that control of SGO1 recruitment to chromosomes is different in plants than in other model organisms.
在减数分裂过程中，姐妹染色单体黏连（SSC）在连续两次核分裂期间的顺序释放，使得二倍体祖细胞能够产生单倍体配子。沿染色体臂的SSC释放首先允许同源染色体进行减数分离，随后，后期II着丝粒黏连的释放允许染色单体分离。守护蛋白（SGO）家族在果蝇和酵母中着丝粒黏连的保护中起主要作用。我们分离出了一个玉米突变体，该突变体在后期I表现出着丝粒黏连的过早丧失。我们表明，这种表型是由于缺少玉米守护蛋白同源物ZmSGO1蛋白所致。我们还表明，ZmSGO1定位于着丝粒。在有丝分裂染色体上未发现ZmSGO1蛋白，并且它没有明显的有丝分裂功能。基于这些结果，我们提出ZmSGO1在减数分裂I期间特异性地维持着丝粒黏连，因此表明SGO1在减数分裂期间的核心功能在不同生物界以及大基因组物种中是保守的。然而，与其他守护蛋白不同，我们在玉米中观察到ZmSGO1的早期且依赖REC8的募集，这表明植物中SGO1募集到染色体上的调控与其他模式生物不同。
