Overexpression of SETβ, a protein localizing to centromeres, causes precocious separation of chromatids during the first meiosis of mouse oocytes
Overexpression of SETβ, a protein localizing to centromeres, causes precocious separation of chromatids during the first meiosis of mouse oocytes
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DOI：
10.1242/jcs.116541
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发表时间：
2013-04-01
影响因子：
4
通讯作者：
Sun, Qing-Yuan
中科院分区：
文献类型：
--
作者：
Qi, Shu-Tao;Wang, Zhen-Bo;Sun, Qing-Yuan
哺乳动物卵母细胞减数分裂中的染色体分离是一个容易出错的过程，这个过程中的任何错误都可能导致非整倍体，这是导致不孕、流产和许多遗传疾病的主要原因。现在众所周知，shugoshin 和蛋白磷酸酶 2A (PP2A) 在第一次减数分裂期间保护着丝粒凝聚方面发挥着重要作用。 PP2A可以拮抗着丝粒处粘连蛋白复合体成员rec8的磷酸化，从而防止rec8裂解，从而维持染色单体的粘连。 SET beta 是一种与 shugoshin 发生物理相互作用并抑制 PP2A 活性的蛋白质。因此，我们假设 SET beta 可能在卵母细胞减数分裂成熟过程中调节凝聚保护和染色体分离。在此，我们首次报道了小鼠卵母细胞减数分裂过程中SET beta的表达、亚细胞定位和功能。免疫印迹分析显示，SETβ的表达水平从卵母细胞减数分裂的生泡期到MII期保持稳定。免疫荧光分析显示，SET beta在生发囊泡阶段在细胞核中积累，而从生发囊泡破裂到MI阶段，SET beta主要针对内部着丝粒区域，并且微弱地定位于染色单体轴。在 MII 阶段，SET beta 仍然定位于内部着丝粒区域，但可能会重新定位到着丝粒，这一过程可能取决于着丝粒上的张力。 SET beta 与 PP2A 在内着丝粒区域部分共定位。小鼠卵母细胞中 SET β 的过度表达导致姐妹染色单体过早分离，但通过 RNAi 消除 SET β 对减数分裂成熟过程几乎没有影响。综上所述，我们的结果表明，SET beta 尽管定位于着丝粒，但对于小鼠卵母细胞减数分裂成熟过程中的染色体分离可能不是必需的，尽管它的强制过度表达会导致染色单体过早分离。
Chromosome segregation in mammalian oocyte meiosis is an error-prone process, and any mistake in this process may result in aneuploidy, which is the main cause of infertility, abortion and many genetic diseases. It is now well known that shugoshin and protein phosphatase 2A (PP2A) play important roles in the protection of centromeric cohesion during the first meiosis. PP2A can antagonize the phosphorylation of rec8, a member of the cohesin complex, at the centromeres and thus prevent cleavage of rec8 and so maintain the cohesion of chromatids. SET beta is a protein that physically interacts with shugoshin and inhibits PP2A activity. We thus hypothesized that SET beta might regulate cohesion protection and chromosome segregation during oocyte meiotic maturation. Here we report for the first time the expression, subcellular localization and functions of SET beta during mouse oocyte meiosis. Immunoblotting analysis showed that the expression level of SET beta was stable from the germinal vesicle stage to the MII stage of oocyte meiosis. Immunofluorescence analysis showed SET beta accumulation in the nucleus at the germinal vesicle stage, whereas it was targeted mainly to the inner centromere area and faintly localized to the interchromatid axes from germinal vesicle breakdown to MI stages. At the MII stage, SET beta still localized to the inner centromere area, but could relocalize to kinetochores in a process perhaps dependent on the tension on the centromeres. SET beta partly colocalized with PP2A at the inner centromere area. Overexpression of SET beta in mouse oocytes caused precocious separation of sister chromatids, but depletion of SET beta by RNAi showed little effects on the meiotic maturation process. Taken together, our results suggest that SET beta, even though it localizes to centromeres, might not be essential for chromosome separation during mouse oocyte meiotic maturation, although its forced overexpression causes premature chromatid separation.