Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0032, Japan.
Nat Cell Biol. 2013 Jul;15(7):786-96. doi: 10.1038/ncb2782. Epub 2013 Jun 16.
Tethering kinetochores at spindle poles facilitates their efficient capture and segregation by microtubules at mitotic onset in yeast. During meiotic prophase of fission yeast, however, kinetochores are detached from the poles, which facilitates meiotic recombination but may cause a risk of chromosome mis-segregation during meiosis. How cells circumvent this dilemma remains unclear. Here we show that an extensive microtubule array assembles from the poles at meiosis I onset and retrieves scattered kinetochores towards the poles to prevent chromosome drift. Moreover, the microtubule-associated protein complex Alp7-Alp14 (the fission yeast orthologues of mammalian TACC-TOG) is phosphorylated by Polo kinase, which promotes its meiosis-specific association to the outer kinetochore complex Nuf2-Ndc80 of scattered kinetochores, thereby assisting in capturing remote kinetochores. Although TOG was recently characterized as a microtubule polymerase, Dis1 (the other TOG orthologue in fission yeast), together with the Dam1 complex, plays a role in microtubule shortening to pull kinetochores polewards. Thus, microtubules and their binding proteins uniquely reconstitute chromosome configuration during meiosis.
在酵母有丝分裂起始时，将动粒系在纺锤体两极上，有助于微管有效地捕获和分离动粒。然而，在裂殖酵母的减数分裂前期，动粒从两极上脱离，这有利于减数分裂重组，但可能在减数分裂过程中导致染色体错误分离的风险。细胞如何规避这个困境尚不清楚。在这里，我们表明，在减数分裂 I 起始时，一个广泛的微管阵列从两极组装，并将分散的动粒向两极拉回，以防止染色体漂移。此外，微管相关蛋白复合物 Alp7-Alp14（裂殖酵母的哺乳动物 TACC-TOG 的同源物）被 Polo 激酶磷酸化，这促进了其减数分裂特异性与分散动粒的外动粒复合物 Nuf2-Ndc80 的结合，从而有助于捕获远程动粒。尽管 TOG 最近被描述为微管聚合酶，但 Dis1（裂殖酵母中的另一个 TOG 同源物）与 Dam1 复合物一起，在微管缩短过程中发挥作用，将动粒拉向两极。因此，微管及其结合蛋白在减数分裂过程中独特地重建了染色体构型。
