Abstract: DNA deaminases of the Aid/Apobec family convert cytosine into uracil and play key roles in acquired and innate immunity. The epigenetic modification by methylation of cytosine in CpG dinucleotides is also mutagenic, but this is thought to occur by spontaneous deamination. Here we show that Aid and Apobec1 are 5-methylcytosine deaminases resulting in a thymine base opposite a guanine. Their action can thus lead to C → T transition mutations in methylated DNA, or in conjunction with repair of the T:G mismatch, to demethylation. The Aid and Apob...
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Topics: 
Biochemistry
Molecular biology