Partial purification and characterization of human 5-methylcytosine-DNA glycosylase.
The molecular mechanisms by which DNA 5-methylcytosine content is modulated are incompletely understood. Reduction of DNA 5-methylcytosine content has been correlated with the transition from hyperplasia to adenoma in the genesis of human adenocarcinoma of the colon. 5-methylcytosine-DNA glycosylase removes 5-methylcytosine from DNA as a free base, but its involvement in this process is unknown. The 5-methylcytosine-DNA glycosylase activity in HeLa nuclear extracts has been partially purified, with a 460-fold enrichment, and characterized. This activity is specific for 5-methylcytosine at CpG sites in fully methylated DNA; hemimethylated DNA is not a significant substrate. DNA containing unmethylated cytosines is not cleaved by the enzyme. There is an absolute requirement for Mg2+ ions for the activity, which is inhibited by EDTA. This 5-methylcytosine-DNA glycosylase activity could be involved in carcinogenesis, transcription, replication, differentiation and development through resultant DNA hypomethylation following enzymatic removal of 5-methylcytosine from DNA.
Vairapandi
M
M
Department of Pathology and Laboratory Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania, USA.
Duker
N J
NJ
D001665:Binding Sites; D002850:Chromatography, Gel; D004247:DNA / Q000378:metabolism; D045647:DNA Glycosylases; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D006367:HeLa Cells; D006493:Heparin / Q000737:chemistry; D006801:Humans; D008745:Methylation; D009699:N-Glycosyl Hydrolases / Q000302:isolation & purification* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000737:chemistry; D012685:Sepharose / Q000737:chemistry; D013379:Substrate Specificity
D009687:Nuclear Proteins; D006493:Heparin; D004247:DNA; D012685:Sepharose; C093335:5-methylcytosine-DNA glycosylase; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases