Ling Hong, Boudsocq François, Woodgate Roger, Yang Wei
Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Mol Cell. 2004 Mar 12;13(5):751-62. doi: 10.1016/s1097-2765(04)00101-7.
Dpo4 from S. Solfataricus, a DinB-like Y family polymerase, efficiently replicates DNA past an abasic lesion. We have determined crystal structures of Dpo4 complexed with five different abasic site-containing DNA substrates and find that translesion synthesis is template directed with the abasic site looped out and the incoming nucleotide is opposite the base 5' to the lesion. The ensuing DNA synthesis generates a -1 frameshift when the abasic site remains extrahelical. Template realignment during primer extension is also observed, resulting in base substitutions or even +1 frameshifts. In the case of a +1 frameshift, the extra nucleotide is accommodated in the solvent-exposed minor groove. In addition, the structure of an unproductive Dpo4 ternary complex suggests that the flexible little finger domain facilitates DNA orientation and translocation during translesion synthesis.
来自嗜热栖热菌的Dpo4是一种DinB样Y家族聚合酶，能有效地越过无碱基损伤进行DNA复制。我们已经确定了Dpo4与五种不同的含无碱基位点的DNA底物形成的复合物的晶体结构，发现跨损伤合成是由模板引导的，无碱基位点形成环状，进入的核苷酸与损伤位点5'端的碱基相对。当无碱基位点保持在螺旋外时，随后的DNA合成会产生-1移码突变。在引物延伸过程中也观察到模板重排，导致碱基替换甚至+1移码突变。在+1移码突变的情况下，额外的核苷酸容纳在溶剂暴露的小沟中。此外，无活性的Dpo4三元复合物的结构表明，灵活的小拇指结构域在跨损伤合成过程中促进了DNA的定向和易位。
