title: Studies of X chromosome DNA methylation in normal human cells.
abstract: Studies of methylation along 28 kilobases of X-chromosome DNA, assayed by Southern blot analysis using cloned X-chromosome-specific probes, indicates that X DNA methylation in normal human cells changes with replication, is not correlated with number of X chromosomes or transcriptional activity, and is less stable and more prevalent than when the human X is in the foreign environment of mouse-human hybrid cells. In contrast with observations of others in heteroploid cells, we observed no derepression of the inactive X in clonal populations of normal human fibroblasts treated with 5-azacytidine. This may reflect the differences in stability of the methylation of the human X in a foreign environment. Our observations preclude ubiquitous methylation differences as the molecular basis for X-chromosome inactivation.
mesh_terms: D001374:Azacitidine / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000502:physiology*; D004262:DNA Restriction Enzymes; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D006822:Hybrid Cells; D008745:Methylation; D010920:Placenta / Q000378:metabolism; D010957:Plasmids; D012730:Sex Chromosomes / Q000378:metabolism*; D014960:X Chromosome / Q000378:metabolism*
chemical_list: D004247:DNA; D004262:DNA Restriction Enzymes; D001374:Azacitidine