Spontaneous mutagenesis in Escherichia coli harbouring plasmid pKM101: DNA sequence analysis of forward lacI- mutations.
To investigate the influence of plasmid pKM101 on spontaneous mutagenesis, 198 lacI- mutations generated in Escherichia coli harbouring pKM101 were characterized at the DNA sequence level. pKM101 by itself did not enhance the lacI- forward mutation frequency. In general, the resultant distribution of mutation highlights particular sequences at which a variety of mutational events repeatedly occur, including 5'-(G/C)TGG-3', 5'-CCAGG-3', 5'-GATC-3' and 5'-TCGCG-3' sequences. Specifically, the distribution of mutation within base substitution and deletion classes distinguishes the pKM101 spectrum from the wild-type distribution (i.e. absence of pKM101). An even distribution amongst base substitutions was observed which corresponds to a 2.9- to 6.3-fold increase in occurrence of low frequency events (A-->G,T,C; G-->C); high frequency events in the wild-type distribution (G-->A,T) were not influenced by the presence of pKM101. One complex event was recovered which was comprised of two base substitutions separated by 4 bp. An 11-fold increase in small deletion events (3-6 bp) was also observed. The observed pKM101 spectrum does not closely resemble the mutational consequences of SOS induction in the absence of mutagenic treatment (recA441 spectrum) but does return a distribution like that obtained in E. coli deficient in polymerase I activity (polA1 spectrum).
Gordon
A J
AJ
Department of Biology, York University, Ontario, Canada.
Bernelot-Moens
C
C
Glickman
B W
BW
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001482:Base Composition; D001483:Base Sequence; D004256:DNA Polymerase I / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D016368:Frameshift Mutation; D005798:Genes, Bacterial; D056968:Lac Repressors; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D009690:Nucleic Acid Conformation; D010641:Phenotype; D010957:Plasmids; D012097:Repressor Proteins / Q000235:genetics*; D017384:Sequence Deletion
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D056968:Lac Repressors; C539064:LacI protein, E coli; D012097:Repressor Proteins; D004256:DNA Polymerase I