Hoerter J, Eisenstark A, Touati D
Division of Biological Sciences, University of Missouri, Columbia 65211.
Mutat Res. 1989 Dec;215(2):161-5. doi: 10.1016/0027-5107(89)90179-6.
In wild-type Escherichia coli, near-ultraviolet radiation (NUV) was only weakly mutagenic. However, in an allelic mutant strain (sodA sodB) that lacks both Mn- and Fe-superoxide dismutase (SOD) and assumed to have excess superoxide anion (O2-), NUV induced a 9-fold increase in mutation above the level that normally occurs in this double mutant. When a sodA sodB double mutant contained a plasmid carrying katG+ (excess HP-I catalase), mutation by NUV was reduced to wild-type (sodA+ sodB+) levels. Also, in the sodA sodB xthA triple mutant, which lacks exonuclease III (exoIII) in addition to SOD, the mutational frequency by NUV was reduced to wild-type levels. This synergistic action of NUV and O2- suggested that pre-mutational lesions occur, with exoIII converting these lesions to stable mutants. Exposure to H2O2 induced a 2.8-fold increase in mutations in sodA sodB double mutants, but was reduced to control levels when a plasmid carrying katG+ was introduced. These results suggest that NUV, in addition to its other effects on cells, increases mutations indirectly by increasing the flux of OH. radicals, possibly by generating excess H2O2.
在野生型大肠杆菌中，近紫外线辐射（NUV）的诱变作用较弱。然而，在一种等位基因突变株（sodA sodB）中，该菌株缺乏锰超氧化物歧化酶（Mn-SOD）和铁超氧化物歧化酶（Fe-SOD），并假定具有过量的超氧阴离子（O2-），NUV诱导的突变比该双突变体中正常发生的水平增加了9倍。当sodA sodB双突变体含有携带katG+（过量的HP-I过氧化氢酶）的质粒时，NUV诱导的突变降低到野生型（sodA+ sodB+）水平。此外，在sodA sodB xthA三突变体中，除了SOD外还缺乏核酸外切酶III（exoIII），NUV引起的突变频率降低到野生型水平。NUV和O2-的这种协同作用表明，在突变前损伤就已发生，exoIII将这些损伤转化为稳定的突变体。暴露于过氧化氢会使sodA sodB双突变体中的突变增加2.8倍，但当引入携带katG+的质粒时，突变率降低到对照水平。这些结果表明，NUV除了对细胞有其他影响外，还可能通过产生过量的过氧化氢来增加羟基自由基的通量，从而间接增加突变。
