Lawrence C W, Borden A, Banerjee S K, LeClerc J E
Department of Biophysics, University of Rochester School of Medicine, NY 14642.
Nucleic Acids Res. 1990 Apr 25;18(8):2153-7. doi: 10.1093/nar/18.8.2153.
We have investigated the mutagenic properties of an abasic site in DNA by transfecting SOS-induced and uninduced cells of E. coli with a single-stranded M13mp7-based vector that carries a single example of this lesion at one or other of two unique and adjacent sites. Random samples of progeny phage were sequenced to determine the nature of the replication events that occurred at and around these locations. 5% to 7% of the vectors could be replicated in SOS-induced cells, but only 0.1% to 0.7% of them gave plaques in the absence of SOS induction. In SOS-induced cells, 93% and 96% of the phage replicated resulted from the insertion of a nucleotide opposite the abasic site, while the remainder resulted from a targeted omission of a single nucleotide. At one of the sites, nucleotide insertions were 54% dAMP, 25% dTMP, 20% dGMP and 1% dCMP. At the other site they were 80% dAMP, 4% dTMP, 15% dGMP and 1% dCMP. The sequence variation in all but two of the 204 sequences analyzed was restricted to the abasic site itself. In the remaining two, a change at the abasic site was accompanied by a mutation at an immediately flanking nucleotide.
我们通过用基于单链M13mp7的载体转染大肠杆菌的SOS诱导细胞和未诱导细胞，研究了DNA中无碱基位点的诱变特性。该载体在两个独特且相邻位点中的一个或另一个位点携带该损伤的单个实例。对后代噬菌体的随机样本进行测序，以确定在这些位置及其周围发生的复制事件的性质。5%至7%的载体可以在SOS诱导的细胞中复制，但在没有SOS诱导的情况下，只有0.1%至0.7%的载体能形成噬菌斑。在SOS诱导的细胞中，93%和96%的复制噬菌体是由于在无碱基位点对面插入了一个核苷酸，其余的则是由于有针对性地缺失了一个核苷酸。在其中一个位点，核苷酸插入的情况是54%为dAMP，25%为dTMP，20%为dGMP，1%为dCMP。在另一个位点，它们分别为80% dAMP、4% dTMP、15% dGMP和1% dCMP。在分析的204个序列中，除了两个序列外，所有序列的变异都局限于无碱基位点本身。在其余两个序列中，无碱基位点的变化伴随着紧邻核苷酸的突变。
