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umuC-Mediated misrepair mutagenesis in Escherichia coli: extent and specificity of SOS mutagenesis

1983; Elsevier BV; Volume: 111; Issue: 1 Linguagem: Inglês

10.1016/0027-5107(83)90007-6

1873-135X

Yukiko Shinoura, Tuneo Ise, Takesi Kato, Barry W. Glickman,

Bacterial Genetics and Biotechnology

The role of the error-prone misrepair pathway in mutagenesis was examined for a series of mutagens in umuC+ and umuC36 strains of Escherichia coli. Mutagenesis by ENU, MNU, MNNG and EMS was independent of the umuC+ gene function, while mutagenesis by MMS, 4NQO, γ-rays and UV was largely umuC+-dependent. Residual mutagenesis following UV-treatment of a umuC− strain showed the same mutational specificity seen in the umuC+ strain. In contrast, the umuC mutation altered specificity substantially in an excision-repair-defective strain that showed a UV-spectrum strikingly different from that seen in an excision-repair-proficient strain. Only one of nine trpE frameshift mutations examined was reverted by UV-light and its reversion was umuC-dependent. In comparison, the dependence of frameshift mutagenesis following ICR 191 treatment was site-specific, suggesting at least two mechanisms of frameshift mutagenesis, one dependent upon misrepair, the other not. The results, together with those of previous reports (Kato and Nakano, 1981; Shinoura et al., 1983), suggest that the umuC+ gene exerts it's mutator activity via misrepair of DNA lesions provoking the induction of all types of mutational events, though following UV-irradiation mainly transition events are recovered.