Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai-400076, India.
Mol Biol Cell. 2023 Oct 1;34(11):ar107. doi: 10.1091/mbc.E22-12-0569. Epub 2023 Aug 9.
During mitosis, the budding yeast, kinetochores remain attached to microtubules, except for a brief period during S phase. Sister-kinetochores separate into two clusters (bilobed organization) upon stable end-on attachment to microtubules emanating from opposite spindle poles. However, in meiosis, the outer kinetochore protein (Ndc80) reassembles at the centromeres much later after prophase I, establishing new kinetochore-microtubule attachments. Perhaps due to this, despite homolog bi-orientation, we observed that the Ndc80 are linearly dispersed between spindle poles during metaphase I of meiosis. The presence of end-on attachment marker Dam1 as a cluster near each pole suggests one of the other possibilities that the pole-proximal and pole-distal kinetochores are attached end-on and laterally to the microtubules, respectively. Colocalization studies of kinetochores and kinesin motors suggest that budding yeast kinesin 5, Cin8, and Kip1 perhaps localize to the end-on attached kinetochores while kinesin 8 and Kip3 resides at all the kinetochores. Our findings, including kinesin 5 and Ndc80 coappearance after prophase I and reduced Ndc80 levels in null mutant, suggest that kinesin motors are crucial for kinetochore reassembly and stability during early meiosis. Thus, this work reports yet another meiosis specific function of kinesin motors.
在有丝分裂过程中，芽殖酵母的动粒与微管保持附着，除了 S 期的短暂时间。姐妹动粒在稳定的端到端附着到来自纺锤体两极的微管上后，分离成两个簇（双叶组织）。然而，在减数分裂中，外动粒蛋白（Ndc80）在前期 I 之后很久才重新组装在着丝粒上，建立新的动粒-微管附着。也许由于这个原因，尽管同源体双定向，我们观察到在减数分裂中期 I 期间，Ndc80 在线性分散在纺锤体两极之间。端到端附着标记物 Dam1 作为每个极附近的簇的存在表明另一种可能性，即极近端和极远端动粒分别以端到端和侧向附着到微管上。动粒和驱动蛋白马达的共定位研究表明，芽殖酵母驱动蛋白 5、Cin8 和 Kip1 可能定位于端到端附着的动粒上，而驱动蛋白 8 和 Kip3 存在于所有的动粒上。我们的发现，包括前期 I 后动粒 5 和 Ndc80 的共出现以及在 null 突变体中 Ndc80 水平降低，表明驱动蛋白对于动粒的重新组装和早期减数分裂的稳定性至关重要。因此，这项工作报告了驱动蛋白在减数分裂中的另一个特定功能。
