title: Presence of a DNA demethylating activity in the nucleus of murine erythroleukemic cells.
abstract: Nucleoplasm prepared from murine erythroleukemia cells was assayed from enzymatic activity which removes methyl groups from DNA methylated at the internal C of the sequence 5'-CCGG-3' (Hpa II sites). Under the conditions of assay, the release of methyl groups was linear with time for 1 h, and up to 2 pmol could be released per microgram of extract protein. The activity was proportional to the amount of added extract and was sensitive to heat ant to proteinase K exposure. The initial velocity was hyperbolic with increasing amounts of substrate, and the Km for methyl groups was estimated to be between 1 and 1.5 microM. These results show that DNA demethylation catalyzed by extracts from cell nuclei can occur in vitro where no DNA synthesis is occurring and suggest that such a process might occur in vivo to alter DNA methylation during differentiation.
mesh_terms: D000818:Animals; D002460:Cell Line; D003596:Cytosine / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism*; D019286:Endopeptidase K; D010450:Endopeptidases / Q000378:metabolism; D005622:Friend murine leukemia virus; D006358:Hot Temperature; D004915:Leukemia, Erythroblastic, Acute / Q000201:enzymology*; D007942:Leukemia, Experimental / Q000201:enzymology*; D051379:Mice; D008837:Micrococcus; D012436:S-Adenosylmethionine / Q000378:metabolism; D013997:Time Factors
chemical_list: D004269:DNA, Bacterial; D012436:S-Adenosylmethionine; D003596:Cytosine; D010450:Endopeptidases; D019286:Endopeptidase K