Calvente A, Viera A, Parra M T, de la Fuente R, Suja J A, Page J, Santos J L, de la Vega C García, Barbero J L, Rufas J S
Departamento de Biología, Facultad de Ciencias, Edificio de Biológicas, Universidad Autónoma de Madrid, 28049 Madrid, Spain.
Chromosoma. 2013 Mar;122(1-2):77-91. doi: 10.1007/s00412-012-0393-6. Epub 2013 Jan 4.
The cohesin complex plays a key role for the maintenance of sister chromatid cohesion and faithful chromosome segregation in both mitosis and meiosis. This complex is formed by two structural maintenance of chromosomes protein family (SMC) subunits and two non-SMC subunits: an α-kleisin subunit SCC1/RAD21/REC8 and an SCC3-like protein. Several studies carried out in different species have revealed that the distribution of the cohesin subunits along the chromosomes during meiotic prophase I is not regular and that some subunits are distinctly incorporated at different cell stages. However, the accurate distribution of the different cohesin subunits in condensed meiotic chromosomes is still controversial. Here, we describe the dynamics of the cohesin subunits SMC1α, SMC3, RAD21 and SA1 during both meiotic divisions in grasshoppers. Although these subunits show a similar patched labelling at the interchromatid domain of metaphase I bivalents, SMCs and non-SMCs subunits do not always colocalise. Indeed, SA1 is the only cohesin subunit accumulated at the centromeric region of all metaphase I chromosomes. Additionally, non-SMC subunits do not appear at the interchromatid domain in either single X or B chromosomes. These data suggest the existence of several cohesin complexes during metaphase I. The cohesin subunits analysed are released from chromosomes at the beginning of anaphase I, with the exception of SA1 which can be detected at the centromeres until telophase II. These observations indicate that the cohesin components may be differentially loaded and released from meiotic chromosomes during the first and second meiotic divisions. The roles of these cohesin complexes for the maintenance of chromosome structure and their involvement in homologous segregation at first meiotic division are proposed and discussed.
黏连蛋白复合体在有丝分裂和减数分裂过程中对于维持姐妹染色单体黏连以及确保染色体准确分离起着关键作用。该复合体由两个染色体结构维持蛋白家族（SMC）亚基和两个非SMC亚基组成：一个α-kleisin亚基SCC1/RAD21/REC8和一个类SCC3蛋白。在不同物种中进行的多项研究表明，在减数分裂前期I期间，黏连蛋白亚基沿染色体的分布并不规则，并且一些亚基在不同细胞阶段有明显的掺入。然而，不同黏连蛋白亚基在浓缩的减数分裂染色体中的准确分布仍存在争议。在此，我们描述了蝗虫减数分裂两个阶段中黏连蛋白亚基SMC1α、SMC3、RAD21和SA1的动态变化。尽管这些亚基在中期I二价体的染色单体间区域显示出相似的斑点状标记，但SMC亚基和非SMC亚基并不总是共定位。实际上，SA1是唯一在所有中期I染色体着丝粒区域积累的黏连蛋白亚基。此外，非SMC亚基在单个X染色体或B染色体的染色单体间区域均未出现。这些数据表明在中期I存在几种黏连蛋白复合体。除了SA1在末期II之前都能在着丝粒处检测到外，所分析的黏连蛋白亚基在后期I开始时从染色体上释放。这些观察结果表明，黏连蛋白组分在第一次和第二次减数分裂期间可能以不同方式加载和从减数分裂染色体上释放。我们提出并讨论了这些黏连蛋白复合体在维持染色体结构中的作用及其在第一次减数分裂中参与同源染色体分离的情况。
