Elevated dNTP levels suppress hyper-recombination in Saccharomyces cerevisiae S-phase checkpoint mutants
Elevated dNTP levels suppress hyper-recombination in Saccharomyces cerevisiae S-phase checkpoint mutants
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DOI：
10.1093/nar/gkp1064
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发表时间：
2010-03-01
影响因子：
14.9
通讯作者：
Chabes, Andrei
中科院分区：
文献类型：
--
作者：
Fasullo, Michael;Tsaponina, Olga;Chabes, Andrei
MEC 1是人类ATR/ATM基因的基本酵母同源物，控制S期检查点并防止DNA复制缓慢区的复制叉崩溃。在同源重组缺陷的rad 52突变体中，亚型mec 1 -21的生存能力降低，表明复制产生重组损伤。我们以前观察到自发姐妹染色单体交换（SCE），异等位基因重组和易位，分别在mec 1 -21突变体的6倍，10倍和30倍高的速率相比，野生型。在这里，我们报告说，超重组表型与较低的脱氧核糖核苷三磷酸（dNTP）水平，相比野生型。通过引入dun 1突变，从而消除了mec 1 -21中核糖核苷酸还原酶的诱导表达，自发SCE率比野生型增加了15倍。所有的超重组表型减少SML 1缺失，增加dNTP水平。dNTP池的测量表明，与野生型相比，mec 1 -21、dun 1和mec 1 -21 dun 1中的dNTP水平显著降低，而mec 1 -21 sml 1、mec 1 -21 dun 1 sml 1和sml 1突变体的dNTP水平相似，高出2倍。有趣的是，与mec 1 - 21 dun 1相比，mec 1 -21 dun 1 sml 1中较高的dNTP水平与类似于2倍的自发诱变率相关。我们认为，特定检查点突变体中较高的dNTP水平抑制了重组损伤的形成。
MEC1, the essential yeast homolog of the human ATR/ATM genes, controls the S-phase checkpoint and prevents replication fork collapse at slow zones of DNA replication. The viability of hypomorphic mec1-21 is reduced in the rad52 mutant, defective in homologous recombination, suggesting that replication generates recombinogenic lesions. We previously observed a 6-, 10- and 30-fold higher rate of spontaneous sister chromatid exchange (SCE), heteroallelic recombination and translocations, respectively, in mec1-21 mutants compared to wild-type. Here we report that the hyper-recombination phenotype correlates with lower deoxyribonucleoside triphosphate (dNTP) levels, compared to wild-type. By introducing a dun1 mutation, thus eliminating inducible expression of ribonucleotide reductase in mec1-21, rates of spontaneous SCE increased 15-fold above wild-type. All the hyper-recombination phenotypes were reduced by SML1 deletions, which increase dNTP levels. Measurements of dNTP pools indicated that, compared to wild-type, there was a significant decrease in dNTP levels in mec1-21, dun1 and mec1-21 dun1, while the dNTP levels of mec1-21 sml1, mec1-21 dun1 sml1 and sml1 mutants were similar to 2-fold higher. Interestingly, higher dNTP levels in mec1-21 dun1 sml1 correlate with similar to 2-fold higher rate of spontaneous mutagenesis, compared to mec1-21 dun1. We suggest that higher dNTP levels in specific checkpoint mutants suppress the formation of recombinogenic lesions.