title: Time dependence of X gene reactivation induced by 5-azacytidine: possible progressive restructuring of chromatin.
abstract: According to the theoretical mechanism of DNA demethylation by 5-azacytidine, the complete demethylation of one site will require two cell divisions. If reexpression is directly related to demethylation, a maximal reexpression is expected after two cell divisions. In a hamster X human hybrid cell line containing an inactive human X chromosome treated by 5-azacytidine, we show that HPRT reactivation frequency is increased more than 10-fold when cells are allowed to divide 14 times before the selection for the HPRT reactivants. We suggest that the delay corresponds to changes in chromatin conformation.
mesh_terms: D044503:5-Methylcytosine; D000818:Animals; D001374:Azacitidine / Q000494:pharmacology*; D002455:Cell Division; D002460:Cell Line; D002843:Chromatin / Q000187:drug effects / Q000648:ultrastructure*; D006224:Cricetinae; D003596:Cytosine / Q000031:analogs & derivatives; D004303:Dosage Compensation, Genetic / Q000187:drug effects*; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D006822:Hybrid Cells / Q000648:ultrastructure; D007041:Hypoxanthine Phosphoribosyltransferase / Q000096:biosynthesis; D008745:Methylation
chemical_list: D002843:Chromatin; D044503:5-Methylcytosine; D003596:Cytosine; D007041:Hypoxanthine Phosphoribosyltransferase; D001374:Azacitidine