Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, USA.
Genetics. 2010 Dec;186(4):1161-73. doi: 10.1534/genetics.110.122663. Epub 2010 Sep 13.
Gross chromosomal rearrangements (GCRs) are large scale changes to chromosome structure and can lead to human disease. We previously showed in Saccharomyces cerevisiae that nearby inverted repeat sequences (∼20-200 bp of homology, separated by ∼1-5 kb) frequently fuse to form unstable dicentric and acentric chromosomes. Here we analyzed inverted repeat fusion in mutants of three sets of genes. First, we show that genes in the error-free postreplication repair (PRR) pathway prevent fusion of inverted repeats, while genes in the translesion branch have no detectable role. Second, we found that siz1 mutants, which are defective for Srs2 recruitment to replication forks, and srs2 mutants had opposite effects on instability. This may reflect separate roles for Srs2 in different phases of the cell cycle. Third, we provide evidence for a faulty template switch model by studying mutants of DNA polymerases; defects in DNA pol delta (lagging strand polymerase) and Mgs1 (a pol delta interacting protein) lead to a defect in fusion events as well as allelic recombination. Pol delta and Mgs1 may collaborate either in strand annealing and/or DNA replication involved in fusion and allelic recombination events. Fourth, by studying genes implicated in suppression of GCRs in other studies, we found that inverted repeat fusion has a profile of genetic regulation distinct from these other major forms of GCR formation.
染色体结构的大片段重排（GCRs）是染色体结构的大规模变化，可能导致人类疾病。我们之前在酿酒酵母中表明，附近的反向重复序列（约 20-200bp 的同源性，由约 1-5kb 隔开）经常融合形成不稳定的双中心和无着丝粒染色体。在这里，我们分析了三组基因的突变体中的反向重复融合。首先，我们表明，无差错复制后修复（PRR）途径中的基因可防止反向重复序列融合，而跨损伤分支中的基因则没有明显作用。其次，我们发现，siz1 突变体（其 Srs2 招募到复制叉的功能缺陷）和 srs2 突变体对不稳定性有相反的影响。这可能反映了 Srs2 在细胞周期不同阶段的不同作用。第三，我们通过研究 DNA 聚合酶的突变体为错误模板转换模型提供了证据；DNA 聚合酶 delta（滞后链聚合酶）和 Mgs1（聚合酶 delta 相互作用蛋白）的缺陷导致融合事件和等位基因重组的缺陷。聚合酶 delta 和 Mgs1 可能在融合和等位基因重组事件涉及的链退火和/或 DNA 复制中协同作用。第四，通过研究其他研究中涉及 GCR 抑制的基因，我们发现反向重复融合的遗传调控模式与其他主要形式的 GCR 形成不同。
