Institute of Cell Biology, University of Bern, Switzerland.
PLoS Genet. 2009 Nov;5(11):e1000722. doi: 10.1371/journal.pgen.1000722. Epub 2009 Nov 13.
DNA double-strand breaks (DSBs) are formed during meiosis by the action of the topoisomerase-like Spo11/Rec12 protein, which remains covalently bound to the 5' ends of the broken DNA. Spo11/Rec12 removal is required for resection and initiation of strand invasion for DSB repair. It was previously shown that budding yeast Spo11, the homolog of fission yeast Rec12, is removed from DNA by endonucleolytic cleavage. The release of two Spo11 bound oligonucleotide classes, heterogeneous in length, led to the conjecture of asymmetric cleavage. In fission yeast, we found only one class of oligonucleotides bound to Rec12 ranging in length from 17 to 27 nucleotides. Ctp1, Rad50, and the nuclease activity of Rad32, the fission yeast homolog of Mre11, are required for endonucleolytic Rec12 removal. Further, we detected no Rec12 removal in a rad50S mutant. However, strains with additional loss of components localizing to the linear elements, Hop1 or Mek1, showed some Rec12 removal, a restoration depending on Ctp1 and Rad32 nuclease activity. But, deletion of hop1 or mek1 did not suppress the phenotypes of ctp1Delta and the nuclease dead mutant (rad32-D65N). We discuss what consequences for subsequent repair a single class of Rec12-oligonucleotides may have during meiotic recombination in fission yeast in comparison to two classes of Spo11-oligonucleotides in budding yeast. Furthermore, we hypothesize on the participation of Hop1 and Mek1 in Rec12 removal.
DNA 双链断裂 (DSB) 在减数分裂过程中由拓扑异构酶样 Spo11/Rec12 蛋白的作用形成,该蛋白与断裂 DNA 的 5' 端共价结合。Spo11/Rec12 的去除对于 DSB 修复的切口和链入侵的起始是必需的。先前的研究表明,芽殖酵母 Spo11,裂殖酵母 Rec12 的同源物,通过核酸内切酶切割从 DNA 上释放。两种 Spo11 结合的寡核苷酸类别的释放,长度不同,导致了不对称切割的推测。在裂殖酵母中,我们只发现了一种长度为 17 到 27 个核苷酸的 Rec12 结合寡核苷酸。Ctp1、Rad50 和 Rad32 的核酸酶活性,裂殖酵母 Mre11 的同源物,对于 Rec12 的核酸内切酶去除是必需的。此外,我们在 rad50S 突变体中没有检测到 Rec12 的去除。然而,在额外缺失定位于线性元件 Hop1 或 Mek1 的组分的菌株中,观察到一些 Rec12 的去除,这种恢复依赖于 Ctp1 和 Rad32 的核酸酶活性。但是,hop1 或 mek1 的缺失并没有抑制 ctp1Delta 和核酸酶失活突变体 (rad32-D65N) 的表型。我们讨论了在裂殖酵母减数分裂重组过程中,与芽殖酵母中的两种 Spo11 寡核苷酸相比,单一类型的 Rec12-寡核苷酸可能对随后的修复产生的影响。此外,我们假设 Hop1 和 Mek1 参与 Rec12 的去除。