美国佐治亚大学的科学家发现了一种对细胞分裂中姐妹染色单体分离起重要作用的蛋白。研究人员发现，使这种蛋白沉默会导致染色体非整倍性或数目异常。
Kelly Dawe及其同事的研究表明，在减数分裂的第一个阶段，决定生殖细胞或配子形成的细胞分裂过程是由着丝粒控制的。着丝粒是染色体中的一种蛋白结构，纺锤丝在细胞分裂期间与之结合，从而使染色体分离。研究人员进一步说明了抑制着丝粒蛋白MIS12如何导致染色体分离失败，并最终使减数分裂的第一个阶段终止的。
这些发现可能会在医药和农业方面具有重要意义。着丝粒非常容易退化和突变。Dawe说这些发现或许能解释“为什么年长的女性生育时要比较年轻女性更容易出现染色体异常的问题。”这些发现还能为从事人工植物染色体研究的科学家提供帮助。Dawe还指出，由于MIS12的原因，早期的人造染色体均在减数分裂过程中以几乎同样的方式失败。对诸如MIS12等蛋白进行修复或许能修正这些作用。（生物谷Bioon.com）
生物谷推荐原始出处：
Nature Cell Biology 11, 1103 - 1108 (2009) 16 August 2009 | doi:10.1038/ncb1923
Fused sister kinetochores initiate the reductional division in meiosis I
Xuexian Li1 & R. Kelly Dawe1,2
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 pole1, 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 yeast4 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 microtubules5, 6, 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 I, 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.
1 Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
2 Department of Genetics, University of Georgia, Athens, GA 30602, USA.
