Influence of uvrB and pKM101 on the spectrum of spontaneous, UV- and gamma-ray-induced base substitutions that revert hisG46 in Salmonella typhimurium
Eisenstadt, E.; Miller, J.K.; Kahng, L.S.; Barnes, W.M.
Mutation Research 210(1): 113-125
1989
ISSN/ISBN: 0027-5107 PMID: 2642598 Document Number: 341681
Oligonucleotide probes were used to identify base substitutions in 1089 revertants of hisG46 in Salmonella typhimurium that arose spontaneously or following irradiation with UV- or .gamma.-rays. The hisG46 allele, carrying a mutant CCC codon (Pro) in place of the wild-type codon CTC (Leu69) reverted via 6 distinguishable mutational events.sbd.C to T transitions at codon sites 1 or 2, C to A or C to G transversions at codon site 1, C to A at codon site 2, and an extragenic suppressor mutation. The distribution of hisG46 revertants differed among treatments and was influenced by the DNA-repair capacity of the bacteria. Plasmid pKM101 enhanced the frequencies of both spontaneous and induced mutations; transversion events were enhanced more efficiently by pKM101 than were transition events. Compared to Uvr+ bacteria, Uvr- bacteria had higher frequencies of spontaneous and induced mutations; transition mutations were enhanced more efficiently than were transversion mutations. The influence of DNA-repair activities on the mutational spectra provides some insights on the origins of spontaneous and UV-induced mutations.