Mechanism of Avoidance of 5-methylcytosine to Thymine Mutations in Bacteria
It has been known for some time that 5-methylcytosine (5meC) in DNA is a mutation hazard, since deamination of 5meC converts it to thymine, a normal base (Lindahl and Nyberg, 1974). Replication of DNA containing such T:G mismatches results in C to T mutations. Sites of cytosine methylation were first recognized to be hotspots for transition mutations in the lacI system of E. coli (Coulondre et al., 1978), and this observation has been confirmed in other E. coli gene systems and has been extended to human cells. Transition mutations in CpG sequences are the largest class of point mutations found in genetic diseases including cancer (Cooper and Youssoufian, 1988; Greenblatt et al., 1994).
KeywordsMismatch Repair Cytosine Methylation Transition Mutation Amber Mutation Short Patch
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