Schaaper R M, Glickman B W
Mol Gen Genet. 1982;185(3):404-7. doi: 10.1007/BF00334131.
The role of pyrimidine dimers in mutagenesis by ultraviolet light was examined by measuring the UV-induced reversion of six different bacteriophage M13 amber mutants for which the neighboring DNA sequences are known. The mutational response at amber (TAG) codons preceded by a guanine or adenine (where no pyrimidine dimer can be formed) were compared with those preceded by thymine or cytosine (where dimer formation is possible). Equivalent levels of UV-induced mutagenesis were observed at both kinds of sites. This observation demonstrates that there is no requirement for a pyrimidine dimer directly at the site of UV-induced mutation in this single-stranded DNA phage. UV irradiation of the phage was also performed in the presence of Ag+ ions, which specifically sensitize the DNA to dimer formation. The two methods of irradiation, when compared at equal survival levels (and presumably equal dimer frequencies), produced equivalent frequencies of reversion of the amber phage. We believe these results indicate that while the presence of pyrimidine dimers may be a prerequisite for UV mutagenesis, the actual mutagenic event can occur at a site some distance removed from a dimer.
通过测量六种不同的噬菌体M13琥珀突变体的紫外线诱导回复突变，研究了嘧啶二聚体在紫外线诱变中的作用，这些突变体的相邻DNA序列是已知的。将琥珀（TAG）密码子前为鸟嘌呤或腺嘌呤（无法形成嘧啶二聚体）时的突变反应与前为胸腺嘧啶或胞嘧啶（可能形成二聚体）时的突变反应进行了比较。在这两种位点均观察到了同等水平的紫外线诱导诱变。这一观察结果表明，在这种单链DNA噬菌体中，紫外线诱导突变的位点并不需要直接存在嘧啶二聚体。还在Ag+离子存在的情况下对噬菌体进行紫外线照射，Ag+离子可使DNA对二聚体形成产生特异性敏感。当在同等存活水平（推测二聚体频率也相同）下比较这两种照射方法时，琥珀噬菌体的回复突变频率相同。我们认为这些结果表明，虽然嘧啶二聚体的存在可能是紫外线诱变的先决条件，但实际的诱变事件可能发生在距二聚体有一定距离的位点。
