Fused sister kinetochores initiate the reductional division in meiosis I
Fused sister kinetochores initiate the reductional division in meiosis I
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DOI：
10.1038/ncb1923
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发表时间：
2009-09-01
影响因子：
21.3
通讯作者：
Dawe, R. Kelly
中科院分区：
文献类型：
--
作者：
Li, Xuexian;Dawe, R. Kelly
在减数分裂 I 期间，基因组通过协调的减数分裂事件减少到单倍体含量。同源染色体排列、重组和分离，而姐妹染色单体共同定向并移动到同一极(1,2)。一些数据表明姐妹着丝粒在中期 I 早期共同定向，并且姐妹染色单体内聚力（需要 Rec8 和 Shugoshin）支持单极定向。然而，目前尚不清楚姐妹动粒在此期间如何作为单一单位发挥作用。在酿酒酵母中鉴定出具有共同定向作用的基因 (monopolin)(3)；然而，它在裂殖酵母中不具有相同的功能(4)，并且在其他物种中没有发现类似的基因。在这里，我们使用核心动粒蛋白 MIS12（微型染色体不稳定性 12）的敲低突变体来解决这个问题。 MIS12 与 NDC80 复合体的碱基结合，而 NDC80 复合体又直接与微管结合 (5-7)。在 MIS12 水平系统性降低的玉米植株中，减数分裂 I 姐妹着丝粒之间可见的 MIS12-NDC80 桥被破坏。动粒在中期 1 分离并随机定向，导致染色体由于染色单体之间正常的凝聚力（以 Shugoshin 为标志）而在后期停滞。数据表明，减数分裂 I 中的姐妹动粒通过共享的微管结合面融合，并且这种直接连接是减数分裂所必需的。
During meiosis I the genome is reduced to the haploid content by a coordinated reductional division event. Homologous chromosomes align, recombine and segregate while the sister chromatids co-orient and move to the same pole(1,2). Several data suggest that sister kinetochores co-orient early in metaphase I and that sister chromatid cohesion (which requires Rec8 and Shugoshin) supports monopolar orientation. Nevertheless, it is unclear how the sister kinetochores function as single unit during this period. A gene (monopolin)(3) with a co-orienting role was identified in Saccharomyces cerevisiae; however, it does not have the same function in fission yeast(4) and no similar genes have been found in other species. Here we pursue this issue using knockdown mutants of the core kinetochore protein MIS12 (minichromosome instability 12). MIS12 binds to base of the NDC80 complex, which in turn binds directly to microtubuies(5-7). In maize plants with systemically reduced levels of MIS12, a visible MIS12-NDC80 bridge between sister kinetochores at meiosis I is broken. Kinetochores separate and orient randomly in metaphase 1, causing chromosomes to stall in anaphase due to normal cohesion, marked by Shugoshin, between the chromatids. The data establish that sister kinetochores in meiosis I are fused by a shared microtubule-binding face and that this direct linkage is required for reductional division.