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首页> 外文期刊>Biochemistry >Hierarchy of DNA Damage Recognition in Escherichia coli Nucleotide Excision Repair
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Hierarchy of DNA Damage Recognition in Escherichia coli Nucleotide Excision Repair

机译：大肠杆菌核苷酸​​切除修复中DNA损伤识别的层次结构

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摘要

DNA damage recognition plays a central role in nucleotide excision repair (NER). Here we present evidence that in Escherichia coli NER, DNA damage is recognized through at least two separate but successive steps, with the first focused on distortions from the normal structure of the DNA double helix (initial recognition) and the second specifically recognizing the type of DNA base modifications (second recognition), after an initial local separation of the DNA strands. DNA substrates containing stereoisomeric (+)- or (-)-trans- or (+)- or (-)-cis-BPDE-N2-dG lesions in DNA duplexes of known conformations were incised by UvrABC nuclease with efficiencies varying by up to 3-fold. However, these stereoisomeric adducts, when positioned in an opened, single-stranded DNA region, were all incised with similar efficiencies and with enhanced rates (by factors of 1.4-6). These bubble substrates were also equally and efficiently incised by UvrBC nuclease without UvrA. Furthermore, removal of the Watson- Crick partner cytosine residue (leaving an abasic site) in the complementary strand opposite a (+)-cis- BPDE-N2-dG lesion led to a significant reduction in both the binding of UvrA and the incision efficiency of UvrABC by a factor of 5. These data suggest that E. coli NER features adynamic two-stage recognition mechanism.
机译：DNA损伤识别在核苷酸切除修复（NER）中起着核心作用。在这里，我们提供的证据表明，在大肠杆菌NER中，DNA损伤是通过至少两个单独但连续的步骤来识别的，第一步骤着眼于DNA双螺旋正常结构的畸变（初始识别），第二步骤专门识别DNA双螺旋的类型。在最初局部分离DNA链后，对DNA碱基进行修饰（第二次识别）。通过UvrABC核酸酶切割在已知构型的DNA双链体中含有立体异构（+）-或（-）-反式-或（+）-或（-）-顺式-BPDE-N2-dG损伤的DNA底物，效率差异最大3倍。但是，这些立体异构体加合物，当置于开放的单链DNA区域中时，均以相似的效率和提高的速率（以1.4-6的倍数）切割。不使用UvrA的UvrBC核酸酶同样有效地切割了这些气泡底物。此外，去除与（+）-顺-BPDE-N2-dG病变相对的互补链中的Watson-Crick伙伴胞嘧啶残基（留下无碱基位点）导致UvrA的结合和切口效率均显着降低UvrABC的浓度是其5倍。这些数据表明E. coli NER具有动态的两阶段识别机制。

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