Roles for the transcription elongation factor NusA in both DNA repair and damage tolerance pathways in Escherichia coli
Roles for the transcription elongation factor NusA in both DNA repair and damage tolerance pathways in Escherichia coli
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DOI：
10.1073/pnas.1005203107
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发表时间：
2010-08-31
影响因子：
11.1
通讯作者：
Walker, Graham C.
中科院分区：
文献类型：
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作者：
Cohen, Susan E.;Lewis, Cindi A.;Walker, Graham C.
我们报告的观察结果表明，转录延伸因子NusA促进了一种以前未被识别的转录偶联修复（TCR），除了它之前提出的在转录过程中招募翻译合成（TLS） DNA聚合酶的作用。此前，我们报道了NusA在物理和遗传上与TLS DNA聚合酶DinB （DNA pol IV）相互作用。我们发现，在允许的温度下，大肠杆菌nusA11（ts）突变株对硝基呋喃酮（NFZ）和4-硝基喹诺酮-1-氧化物高度敏感，但对紫外线辐射不敏感。基因表达谱表明，这种敏感性不太可能是由于影响已知DNA修复或损伤耐受途径的基因表达的间接影响。我们证明了n -2-糠酰- dg （N-2-f-dG）损伤，NFZ产生的主要损伤的结构类似物，当存在于转录链时，阻断大肠杆菌RNA聚合酶（RNAP）的转录，而不存在于非转录链时。我们的遗传分析表明，NusA参与核苷酸切除修复（NER）依赖的过程，以促进NFZ抗性。我们提供的证据表明，转录在NFZ诱导的损伤的修复中发挥作用，通过分离RNAP突变体，显示出在NFZ暴露下生存能力的改变。我们提出，NusA参与了另一类TCR，涉及识别和去除一类病变，如N-2-f-dG病变，除了在RNAP遇到的间隙处招募DinB用于TLS之外，还可以准确有效地绕过DinB。
We report observations suggesting that the transcription elongation factor NusA promotes a previously unrecognized class of transcription-coupled repair (TCR) in addition to its previously proposed role in recruiting translesion synthesis (TLS) DNA polymerases to gaps encountered during transcription. Earlier, we reported that NusA physically and genetically interacts with the TLS DNA polymerase DinB (DNA pol IV). We find that Escherichia coli nusA11(ts) mutant strains, at the permissive temperature, are highly sensitive to nitrofurazone (NFZ) and 4-nitroquinolone-1-oxide but not to UV radiation. Gene expression profiling suggests that this sensitivity is unlikely to be due to an indirect effect on gene expression affecting a known DNA repair or damage tolerance pathway. We demonstrate that an N-2-furfuryl-dG (N-2-f-dG) lesion, a structural analog of the principal lesion generated by NFZ, blocks transcription by E. coli RNA polymerase (RNAP) when present in the transcribed strand, but not when present in the nontranscribed strand. Our genetic analysis suggests that NusA participates in a nucleotide excision repair (NER)-dependent process to promote NFZ resistance. We provide evidence that transcription plays a role in the repair of NFZ-induced lesions through the isolation of RNAP mutants that display altered ability to survive NFZ exposure. We propose that NusA participates in an alternative class of TCR involved in the identification and removal of a class of lesion, such as the N-2-f-dG lesion, which are accurately and efficiently bypassed by DinB in addition to recruiting DinB for TLS at gaps encountered by RNAP.