Tang M, Pham P, Shen X, Taylor J S, O'Donnell M, Woodgate R, Goodman M F
Department of Biological Sciences and Chemistry, University of Southern California, University Park, Los Angeles 90089-1340, USA.
Nature. 2000 Apr 27;404(6781):1014-8. doi: 10.1038/35010020.
The expression of the Escherichia coli DNA polymerases pol V (UmuD'2C complex) and pol IV (DinB) increases in response to DNA damage. The induction of pol V is accompanied by a substantial increase in mutations targeted at DNA template lesions in a process called SOS-induced error-prone repair. Here we show that the common DNA template lesions, TT (6-4) photoproducts, TT cis-syn photodimers and abasic sites, are efficiently bypassed within 30 seconds by pol V in the presence of activated RecA protein (RecA*), single-stranded binding protein (SSB) and pol III's processivity beta,gamma-complex. There is no detectable bypass by either pol IV or pol III on this time scale. A mutagenic 'signature' for pol V is its incorporation of guanine opposite the 3'-thymine of a TT (6-4) photoproduct, in agreement with mutational spectra. In contrast, pol III and pol IV incorporate adenine almost exclusively. When copying undamaged DNA, pol V exhibits low fidelity with error rates of around 10(-3) to 10(-4), with pol IV being 5- to 10-fold more accurate. The effects of RecA protein on pol V, and beta,gamma-complex on pol IV, cause a 15,000- and 3,000-fold increase in DNA synthesis efficiency, respectively. However, both polymerases exhibit low processivity, adding 6 to 8 nucleotides before dissociating. Lesion bypass by pol V does not require beta,gamma-complex in the presence of non-hydrolysable ATPgammaS, indicating that an intact RecA filament may be required for translesion synthesis.
大肠杆菌DNA聚合酶pol V（UmuD'2C复合物）和pol IV（DinB）的表达会因DNA损伤而增加。pol V的诱导伴随着在一个称为SOS诱导易错修复的过程中，针对DNA模板损伤的突变大量增加。在这里，我们表明，在存在活化的RecA蛋白（RecA*）、单链结合蛋白（SSB）和pol III的持续性β,γ复合物的情况下，pol V能在30秒内有效地绕过常见的DNA模板损伤，即TT（6-4）光产物、TT顺式-反式光二聚体和无碱基位点。在此时间范围内，pol IV或pol III均未检测到绕过现象。pol V的诱变“特征”是其在TT（6-4）光产物的3'-胸腺嘧啶对面掺入鸟嘌呤，这与突变谱一致。相比之下，pol III和pol IV几乎只掺入腺嘌呤。当复制未受损的DNA时，pol V表现出低保真性，错误率约为10^(-3)至10^(-4)，而pol IV的准确性要高5至10倍。RecA蛋白对pol V的作用以及β,γ复合物对pol IV的作用，分别使DNA合成效率提高了15000倍和3000倍。然而，这两种聚合酶的持续性都很低，在解离前只能添加6至8个核苷酸。在存在不可水解的ATPγS的情况下，pol V绕过损伤不需要β,γ复合物，这表明跨损伤合成可能需要完整的RecA丝。
