DNA SEQUENCE ANALYSIS OF MUTAGENICITY AND SITE SPECIFICITY OF ETHYL METHANESULFONATE IN Uvr+ AND UvrB - STRAINS OF ESCHERICHIA COLI

• Published in: Genetics (Austin) Vol. 113; no. 4; pp. 811 - 819
• Main Authors: Burns, Philip A, Allen, Frances L, Glickman, Barry W
• Format: Journal Article
• Language: English
• Published: United States Genetics Soc America 01.08.1986
• Subjects: Base Sequence; Cloning, Molecular; DNA, Bacterial - genetics; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - radiation effects; Ethyl Methanesulfonate - pharmacology; Genes, Bacterial - drug effects; Investigations; Mutation; Species Specificity; Ultraviolet Rays
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/113.4.811

EMS-induced mutations within a 180 base pair region of the lacI gene of E. coli were cloned and sequenced. In total, 105 and 79 EMS-induced mutations from a Uvr+ and a UvrB- strain, respectively, were sequenced. The specificity of EMS-induced mutagenesis was very similar in the two strians; G:C → A:T transitions accounted for all but three of the mutants. The overall frequency of induced mutation was fivefold higher in the UvrB- strain compared to the Uvr+ strain. This demonstrates, at the DNA sequence level, that the presumed pre-mutagenic lesion, O  6-ethylguanine, is subject to repair by the uvrABC excision repair system of E. coli. An analysis of mutation frequencies with respect to neighboring base sequence, in the two strains, shows that O  6-ethylguanine lesions adjacent to A:T base pairs present better targets for the excision repair machinery than those not adjacent to A:T base pairs.