Bridges B A, Bates H
MRC Cell Mutation Unit, University of Sussex, Falmer, Brighton, UK.
Mutagenesis. 1990 Jan;5(1):35-8. doi: 10.1093/mutage/5.1.35.
UV light was unable to induce rifampicin-resistant mutations at 43 degrees C in Escherichia coli ER11 dnaE486. Although DnaE486 gene product is inactive at 43 degrees C, these bacteria contain the pcbA1 mutation which allows DNA replication provided DNA polymerase I is functional. The experiments were carried out under conditions where full expression of rifampicin-resistant mutations could occur so that the lack of induced mutations cannot be ascribed to an effect of incubation at 43 degrees C on mutation expression. UV-mutability at 43 degrees C was restored by the presence of the dnaE+ allele on a plasmid. It is concluded that functional DnaE protein is essential for UV mutagenesis. The dnaE486 mutation also blocked the induction at 43 degrees C of mutations induced by UV plus delayed photoreversal, a procedure that has been postulated to reflect an early misincorporation step in the UV mutagenic process.
紫外线无法在43摄氏度下诱导大肠杆菌ER11 dnaE486产生利福平抗性突变。尽管DnaE486基因产物在43摄氏度时无活性，但这些细菌含有pcbA1突变，只要DNA聚合酶I有功能，就允许DNA复制。实验是在能够充分表达利福平抗性突变的条件下进行的，因此诱导突变的缺乏不能归因于在43摄氏度下孵育对突变表达的影响。质粒上存在dnaE +等位基因可恢复43摄氏度时的紫外线诱变能力。得出的结论是，功能性DnaE蛋白对于紫外线诱变至关重要。dnaE486突变也阻断了在43摄氏度下由紫外线加延迟光逆转诱导的突变，这一过程被认为反映了紫外线诱变过程中的早期错配步骤。
