Wells Jennifer L, Pryce David W, McFarlane Ramsay J
North West Cancer Research Fund Institute, University of Wales Bangor, Memorial Building, Bangor, Gwynedd, L57 2UW, UK.
Yeast. 2006 Oct 15;23(13):977-89. doi: 10.1002/yea.1403.
Homologous chromosome pairing is a central feature of meiosis I, contributing to the correct segregation of chromosomes during meiosis. The fission yeast, Schizosaccharomyces pombe, has been widely used to study meiotic chromosome dynamics, partly because studies in this yeast are simplified due to the lack of post-pairing synaptic structures. Chromosome pairing in Sz. pombe occurs differentially throughout the genome. Telomeres cluster at the spindle pole body (SPB) at the onset of meiosis, imposing a spatial restriction on pairing events. Subsequently, centromeres dissociate from the SPB and pair in a recombination- and heterochromatin (Swi6)-independent fashion. Pairing of telomere distal regions occurs during meiotic prophase, concomitant with a dynamic association/dissociation of homologous regions, with interhomologue associations becoming increasingly stable. The stabilization of paired regions is enhanced by factors required for the initiation of meiotic recombination, suggesting that recombination stabilizes paired regions. However, substantial pairing is initiated in the absence of recombination; this is dependent upon another factor, the conserved Meu13 protein, demonstrating that recombination is not required for initial pairing interactions. During meiotic prophase Sz. pombe exhibits a pronounced dynein-dependent nuclear oscillation, which drives the pairing of centromeric and interstitial regions. Dynein is also required for the significant levels of achiasmate reductional segregation observed in Sz. pombe, possibly implicating the centromere-associated pairing with achiasmate homologue segregation. Whilst Sz. pombe does not form discernable synaptic structures continuously along the meiotic chromosomes, it does form proteinacious, meiosis-specific, linear structures (linear elements). However, the role, if any, of these structures in mediating homologue pairing is unknown.
同源染色体配对是减数分裂I的核心特征，有助于减数分裂过程中染色体的正确分离。裂殖酵母粟酒裂殖酵母已被广泛用于研究减数分裂染色体动力学，部分原因是由于缺乏配对后突触结构，该酵母中的研究得以简化。粟酒裂殖酵母中的染色体配对在整个基因组中差异发生。减数分裂开始时，端粒聚集在纺锤体极体（SPB）上，对配对事件施加空间限制。随后，着丝粒与SPB解离并以不依赖重组和异染色质（Swi6）的方式配对。端粒远端区域的配对发生在减数分裂前期，伴随着同源区域的动态关联/解离，同源物之间的关联变得越来越稳定。减数分裂重组起始所需的因子增强了配对区域的稳定性，这表明重组稳定了配对区域。然而，在没有重组的情况下也会启动大量配对；这依赖于另一个因子，即保守的Meu13蛋白，这表明初始配对相互作用不需要重组。在减数分裂前期，粟酒裂殖酵母表现出明显的动力蛋白依赖性核振荡，这驱动着丝粒和中间区域的配对。动力蛋白对于粟酒裂殖酵母中观察到的大量无交叉减数分裂分离也是必需的，这可能意味着着丝粒相关配对与无交叉同源物分离有关。虽然粟酒裂殖酵母不会沿着减数分裂染色体连续形成可辨别的突触结构，但它确实会形成蛋白质性的、减数分裂特异性的线性结构（线性元件）。然而，这些结构在介导同源物配对中的作用（如果有）尚不清楚。
