Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
PLoS One. 2012;7(12):e51540. doi: 10.1371/journal.pone.0051540. Epub 2012 Dec 20.
The Smc5-Smc6 complex in Saccharomyces cerevisiae is both essential for growth and important for coping with genotoxic stress. While it facilitates damage tolerance throughout the genome under genotoxin treatment, its function during unperturbed growth is mainly documented for repetitive DNA sequence maintenance. Here we provide physical and genetic evidence showing that the Smc5-Smc6 complex regulates recombination at non-repetitive loci such as centromeres in the absence of DNA damaging agents. Mutating Smc6 results in the accumulation of recombination intermediates at centromeres and other unique sequences as assayed by 2D gel analysis. In addition, smc6 mutant cells exhibit increased levels of Rad52 foci that co-localize with centromere markers. A rad52 mutation that decreases centromeric, but not overall, levels of Rad52 foci in smc6 mutants suppresses the nocodazole sensitivity of these cells, suggesting that the Smc6-mediated regulation of recombination at centromeric regions impacts centromere-related functions. In addition to influencing recombination, the SUMO ligase subunit of the Smc5-Smc6 complex promotes the sumoylation of two kinetochore proteins and affects mitotic spindles. These results suggest that the Smc5-Smc6 complex regulates both recombination and kinetochore sumoylation to facilitate chromosomal maintenance during growth.
酿酒酵母中的 Smc5-Smc6 复合物对于生长是必需的,对于应对遗传毒性应激也很重要。虽然它在遗传毒物处理下有助于基因组中的损伤容忍,但在未受干扰的生长过程中,其功能主要是为重复 DNA 序列维持提供证明。在这里,我们提供物理和遗传证据表明,Smc5-Smc6 复合物在没有 DNA 损伤剂的情况下调节着着丝粒等非重复基因座的重组。通过二维凝胶分析,Smc6 的突变导致着丝粒和其他独特序列处的重组中间体积累。此外,smc6 突变体细胞表现出 Rad52 焦点水平升高,这些焦点与着丝粒标记物共定位。降低 smc6 突变体细胞中着丝粒而非整体 Rad52 焦点水平的 rad52 突变抑制了这些细胞对诺考达唑的敏感性,表明 Smc6 介导的着丝粒区域重组调控影响着丝粒相关功能。除了影响重组外,Smc5-Smc6 复合物的 SUMO 连接酶亚基还促进了两个着丝粒蛋白的 SUMO 化,并影响了有丝分裂纺锤体。这些结果表明,Smc5-Smc6 复合物调节重组和着丝粒 SUMO 化,以促进生长过程中的染色体维持。