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The Influence of DNA Repair by Ogt Alkyltransferase on the Distribution of Alkylnitrosourea‐Induced Mutations in Escherichia coli
Author(s) -
Vidal Antonio,
Abril Nieves,
Pueyo Carmen
Publication year - 1997
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/(sici)1098-2280(1997)29:2<180::aid-em9>3.0.co;2-i
Subject(s) - mutagenesis , dna , dna repair , mutation , biology , escherichia coli , microbiology and biotechnology , biochemistry , genetics , gene
To determine the influence of DNA repair by Ogt alkyltransferase on the distribution of alkylnitrosourea‐induced mutations, we have analysed in Ogt‐proficient and Ogt‐deficient bacterial strains the DNA sequence changes of a total of 357 independent mutations occurring within the initial part of the lacI gene of Escherichia coli. The majority (>80%) of mutations induced by either N ‐ethyl‐ N ‐nitrosourea (ENU) or N ‐methyl‐ N ‐nitrosourea (MNU) in the two genetic backgrounds were G:C → A:T transitions, consistent with the predominant role of the O 6 ‐alkylguanine miscoding lesion in mutagenesis by alkylating agents. The analysis of the distribution of G:C → A:T transitions induced by ENU in Ogt + and Ogt ‐ bacteria reveals an influence of the 5′‐flanking base at the level of repair by Ogt alkyltransferase. The Ogt protein appears more efficient at repairing O 6 ‐ethylguanine lesions, which are flanked 5′ by a G or C, in agreement with previously reported data from our group for ethylmethane sulfonate. In contrast, no preference could be inferred for the repair of O 6 ‐methylguanine lesions by Ogt protein. These results seem to indicate that the preference of the Ogt alkyltransferase to repair certain DNA sequences might be a function of the size of the alkyl group. The importance of the alkyl group length has been described also at the level of the (A)BC excinuclease machinery that seems to have a DNA sequence specificity opposite to that of Ogt alkyltransferase. © 1997 Wiley‐Liss, Inc.