Stimulation of Chromosomal Rearrangements by Ribonucleotides
Stimulation of Chromosomal Rearrangements by Ribonucleotides
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DOI：
10.1534/genetics.115.181149
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发表时间：
2015-11-01
期刊：
影响因子：
3.3
通讯作者：
Argueso, Juan Lucas
中科院分区：
文献类型：
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作者：
Conover, Hailey N.;Lujan, Scott A.;Argueso, Juan Lucas
我们通过全基因组序列分析表明，在含有pol2-M644G等位基因的酵母二倍体菌株中，RNase H2活性的丧失会增加杂合性（LOH）的丧失，该等位基因编码DNA聚合酶epsilon的突变版本，从而增加核糖核苷酸的结合。因此，我们分析了编码RNase H2亚基（rnh201 Delta、rnh202 Delta和rnh203 Delta）、拓扑异构酶1 （TOP1 Delta）和/或携带DNA聚合酶e、a和Delta突变等位基因缺失的突变二倍体菌株中RNase H2缺失对LOH和非等位基因同源重组（NAHR）的影响。我们观察到编码野生型DNA聚合酶的RNase H2突变体的LOH率升高了7倍。携带pol2-M644G等位基因的菌株的LOH率提高了7倍，与rnh201 Delta联合作用时LOH率提高了23倍。相比之下，携带减少核糖核苷酸掺入的pol2-M644L突变的菌株表现出较低的LOH率。携带pol1-L868M或pol3-L612M等位基因的菌株，在聚合酶a和d合成DNA时，LOH率没有升高，这导致核糖核苷酸的掺入增加。在NAHR分析中也观察到类似的趋势，尽管表型差异较小。核糖核苷酸介导的LOH和NAHR率的增加强烈依赖于TOP1。这些数据增加了最近关于核糖核苷酸的不对称诱变性的报道，这种诱变性是由DNA复制过程中核糖核苷酸的拓扑异构酶1加工引起的。
We show by whole genome sequence analysis that loss of RNase H2 activity increases loss of heterozygosity (LOH) in Saccharomyces cerevisiae diploid strains harboring the pol2-M644G allele encoding a mutant version of DNA polymerase epsilon that increases ribonucleotide incorporation. This led us to analyze the effects of loss of RNase H2 on LOH and on nonallelic homologous recombination (NAHR) in mutant diploid strains with deletions of genes encoding RNase H2 subunits (rnh201 Delta, rnh202 Delta, and rnh203 Delta), topoisomerase 1 (TOP1 Delta), and/or carrying mutant alleles of DNA polymerases e, a, and delta. We observed an similar to 7-fold elevation of the LOH rate in RNase H2 mutants encoding wild-type DNA polymerases. Strains carrying the pol2-M644G allele displayed a 7-fold elevation in the LOH rate, and synergistic 23-fold elevation in combination with rnh201 Delta. In comparison, strains carrying the pol2-M644L mutation that decreases ribonucleotide incorporation displayed lower LOH rates. The LOH rate was not elevated in strains carrying the pol1-L868M or pol3-L612M alleles that result in increased incorporation of ribonucleotides during DNA synthesis by polymerases a and d, respectively. A similar trend was observed in an NAHR assay, albeit with smaller phenotypic differentials. The ribonucleotide-mediated increases in the LOH and NAHR rates were strongly dependent on TOP1. These data add to recent reports on the asymmetric mutagenicity of ribonucleotides caused by topoisomerase 1 processing of ribonucleotides incorporated during DNA replication.