title: Direct correlation between methylation status and expression of the human O-6-methylguanine DNA methyltransferase gene.
abstract: To assess the role of DNA cytosine methylation in the expression of the O-6-methylguanine DNA methyltransferase (MGMT) gene, the methylation status of selected CpG-containing dinucleotides in and surrounding the coding regions of the gene were examined and correlated with steady state expression of MGMT mRNA in 13 human cell lines. Additionally, tumor cells which exhibited very high levels of MGMT expression were chronically exposed to 5-azacytidine to assess the effects of changes in gene methylation on MGMT expression. Results of these studies demonstrate that the degree of methylation of multiple MGMT gene regions correlates with gene expression, but in a direct rather than an inverse fashion, and that 5-azacytidine-induced demethylation of the MGMT gene correlates with a significant reduction, rather than induction, of MGMT steady-state mRNA expression. These results suggest a unique, potentially alterable methylation-related regulatory mechanism for the MGMT gene.
authors.affiliation: Department of Medicine, Stritch School of Medicine, Loyola University Medical Center, Maywood, IL 60153.
authors.forename: R O
authors.initials: RO
authors.lastname: Pieper
authors.forename: J F
authors.initials: JF
authors.lastname: Costello
authors.forename: R A
authors.initials: RA
authors.lastname: Kroes
authors.forename: B W
authors.initials: BW
authors.lastname: Futscher
authors.forename: U
authors.initials: U
authors.lastname: Marathi
authors.forename: L C
authors.initials: LC
authors.lastname: Erickson
mesh_terms: D001374:Azacitidine / Q000494:pharmacology; D015152:Blotting, Northern; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008745:Methylation / Q000187:drug effects; D008780:Methyltransferases / Q000235:genetics*; D019853:O(6)-Methylguanine-DNA Methyltransferase; D012333:RNA, Messenger / Q000032:analysis; D012334:RNA, Neoplasm / Q000032:analysis; D015183:Restriction Mapping; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
chemical_list: D012333:RNA, Messenger; D012334:RNA, Neoplasm; D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase; D001374:Azacitidine