Molecular basis of base substitution hotspots in Escherichia coli

Abstract
In the lacI gene of E. coli spontaneous base substitution hotspots occur at 5-methylcytosine residues. The hotspots disappear when the respective cytosines are not methylated. The hotspots may result from the spontaneous deamination of 5-methylcytosine to thymine, which is not excised by the enzyme DNA-uracil glycosidase.