减数分裂中的第二次细胞分裂

佚名

生物谷报道：本周Nature揭示了减数分裂中的一个关键环节的机理，减数分裂指的是将生殖细胞中的染色体数量从双倍体减少为单倍体的细胞分裂过程，涉及一个DNA复制周期和两次细胞分裂。在第二次细胞分裂过程（减数分裂-II）中，姐妹染色单体分离，每个子细胞将每个染色体各接受一份，形成一个单倍体合子。在减数分裂-I中，姐妹染色单体需要一起连接在它们的端粒上，但保护这种端粒连接、使其不致分离的因素却难以确定。现在，Kitajima等人发现了一种蛋白。名为Shugoshin，它在裂殖酵母的减数分裂-I期间保护端粒连接。具有类似序列的蛋白也存在于果蝇和哺乳动物中，说明该蛋白被广泛保留了下来，一种“有丝分裂”版本存在于酵母中。人类的Shugoshin类蛋白最近被发现是一种抗原，在多数乳腺癌患者中该蛋白水平升高，说明它可能是有丝分裂染色体分离所需的一种致癌蛋白。

The conserved kinetochore protein shugoshin protects centromeric cohesion during meiosis

Nature 427, 510 - 517 (05 February 2004）

Meiosis comprises a pair of specialized nuclear divisions that produce haploid germ cells. To accomplish this, sister chromatids must segregate together during the first meiotic division (meiosis I), which requires that sister chromatid cohesion persists at centromeres. The factors that protect centromeric cohesion during meiosis I have remained elusive. Here we identify Sgo1 (shugoshin), a protector of the centromeric cohesin Rec8 in fission yeast. We also identify a homologue of Sgo1 in budding yeast. We provide evidence that shugoshin is widely conserved among eukaryotes. Moreover, we identify Sgo2, a paralogue of shugoshin in fission yeast, which is required for faithful mitotic chromosome segregation. Localization of Sgo1 and Sgo2 at centromeres requires the kinase Bub1, identifying shugoshin as a crucial target for the kinetochore function of Bub1. These findings provide insights into the evolution of meiosis and kinetochore regulation during mitosis and meiosis.