Stalled transcription complexes promote DNA repair at a distance
Stalled transcription complexes promote DNA repair at a distance
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DOI：
10.1073/pnas.1322350111
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发表时间：
2014-03-18
影响因子：
11.1
通讯作者：
Savery, Nigel J.
中科院分区：
文献类型：
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作者：
Haines, Nia M.;Kim, Young-In T.;Savery, Nigel J.
转录偶联核苷酸切除修复（TCR）加速从活性基因的模板链去除非编码损伤，因此有助于基因组范围内突变频率的变化。目前的TCR模型假设，如果病变要成为加速修复的底物，它必须引起RNA聚合酶（RNAP）停止。我们已经研究了TCR使用的系统中，转录停滞和损伤的位置可以解耦的基板要求。我们表明，MFD依赖性TCR在细菌中涉及的损伤搜索复合物的形成，可以检测到病变的下游停滞RNAP，和链特异性的加速修复途径是独立的病变停滞RNAP的要求。我们还表明，一个OP（操纵子极性抑制）转录暂停网站，这会导致回溯RNAP，可以促进修复下游病变时，这些病变本身不会导致聚合酶停止。我们的研究结果表明，转录修复偶联因子Mfd，这是一个ATP依赖性超家族2解旋酶结合RNAP，继续易位沿着DNA RNAP后已被取代，直到在模板链中的病变被定位。暂停位点可以促进非停滞性损伤的修复，这一发现表明TCR途径在调节基因组不同部分的突变频率方面可能发挥着比以前怀疑的更广泛的作用。
Transcription-coupled nucleotide excision repair (TCR) accelerates the removal of noncoding lesions from the template strand of active genes, and hence contributes to genome-wide variations in mutation frequency. Current models for TCR suppose that a lesion must cause RNA polymerase (RNAP) to stall if it is to be a substrate for accelerated repair. We have examined the substrate requirements for TCR using a system in which transcription stalling and damage location can be uncoupled. We show that Mfd-dependent TCR in bacteria involves the formation of a damage search complex that can detect lesions downstream of a stalled RNAP, and that the strand specificity of the accelerated repair pathway is independent of the requirement for a lesion to stall RNAP. We also show that an ops (operon polarity suppressor) transcription pause site, which causes backtracking of RNAP, can promote the repair of downstream lesions when those lesions do not themselves cause the polymerase to stall. Our findings indicate that the transcription-repair coupling factor Mfd, which is an ATP-dependent superfamily 2 helicase that binds to RNAP, continues to translocate along DNA after RNAP has been displaced until a lesion in the template strand is located. The discovery that pause sites can promote the repair of nonstalling lesions suggests that TCR pathways may play a wider role in modulating mutation frequencies in different parts of the genome than has previously been suspected.