Estradiol receptor potentiates, in vitro, the activity of 5-methylcytosine DNA glycosylase.

At a concentration of 5 x 10(-9) M of hemi-methylated DNA (one order of magnitude below the K(m)), MCF-7 (a human breast carcinoma cell line) nuclear extracts potentiate the activity of 5-methylcytosine DNA glycosylase (5-MCDG, alias G/T mismatch DNA glycosylase). Depending on the ratio between MCF-7 nuclear extracts and 5-MCDG, there is an up to 10-fold increase in 5-MCDG activity. The potentiation of 5-MCDG by MCF-7 nuclear extracts requires an estradiol response element adjacent to the hemi-methylated site.

5-Methyldeoxycytidine monophosphate deaminase and 5-methylcytidyl-DNA deaminase activities are present in human mature sperm cells.

Human mature sperm cells have a high nuclease and 5-methyldeoxycytidine monophosphate (5-mdCMP) deaminase activity. The deaminase converts the nuclease degradation product 5-mdCMP into dTMP which is further cleaved into thymine and the abasic sugar-phosphate. Both 5-methylcytidine 5' and 3' monophosphates are good substrates for the deaminase.