Rabkin S D, Moore P D, Strauss B S
Proc Natl Acad Sci U S A. 1983 Mar;80(6):1541-5. doi: 10.1073/pnas.80.6.1541.
A variety of DNA polymerases, synthesizing in vitro on an UV-irradiated phi X174 DNA template, terminate synthesis one nucleotide before the 3' pyrimidines of putative dimers on the template. We have devised a system using Escherichia coli DNA polymerase I (Klenow fragment) that can synthesize past at least some of these dimers. The bypass is carried out in a multistep process--first, the incorporation of nucleotides opposite the pyrimidines in the dimer and, then, the addition of nucleotides complementary to the bases distal to the dimer. The insertion of a nucleotide opposite the first (3') pyrimidine of a putative dimer in the presence of Mn2+ occurs in a concentration-dependent fashion with a 3- to 4-fold preference for purine nucleotides over pyrimidine nucleotides. In the presence of Mg2+, insertion is less frequent. Correlation of these results with in vivo mutation data suggests a role for the polymerase in determining the spectrum of base substitution mutagenesis in SOS induced cells.
多种DNA聚合酶在紫外线照射的φX174 DNA模板上进行体外合成时，会在模板上假定二聚体的3'嘧啶前一个核苷酸处终止合成。我们设计了一种使用大肠杆菌DNA聚合酶I（克列诺片段）的系统，该系统能够越过至少一些此类二聚体进行合成。越过过程分多步进行——首先，在二聚体中的嘧啶相对位置掺入核苷酸，然后，添加与二聚体远端碱基互补的核苷酸。在Mn2+存在的情况下，在假定二聚体的第一个（3'）嘧啶相对位置插入核苷酸以浓度依赖方式发生，对嘌呤核苷酸的偏好比对嘧啶核苷酸高3至4倍。在Mg2+存在的情况下，插入频率较低。这些结果与体内突变数据的相关性表明，该聚合酶在确定SOS诱导细胞中碱基取代诱变谱方面发挥作用。
