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Methylation of selected CpGs in the human O 6 ‐methylguanine‐DNA methyltransferase promoter region as a marker of gene silencing
Author(s) -
Danam Rebecca Prapurna,
Qian Xilin C.,
Howell Sherie R.,
Brent Thomas P.
Publication year - 1999
Publication title -
molecular carcinogenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.254
H-Index - 97
eISSN - 1098-2744
pISSN - 0899-1987
DOI - 10.1002/(sici)1098-2744(199902)24:2<85::aid-mc2>3.0.co;2-c
Subject(s) - methylation , biology , methyltransferase , dna methylation , cpg site , gene silencing , bisulfite sequencing , o 6 methylguanine dna methyltransferase , dna methyltransferase , microbiology and biotechnology , cancer research , gene , genetics , gene expression
Abstract O 6 ‐Methylguanine‐DNA methyltransferase (MGMT) is a major determinant of susceptibility to methylating carcinogens and of tumor resistance to anticancer methylating and chloroethylating drugs. The silencing of MGMT expression that occurs in 20–30% of human tumor lines is tightly linked to methylation within the MGMT gene 5′ CpG island. Previous studies on a very limited number of cell lines showed that such methylation was uneven, with hot‐spots where methylation almost invariably occurred and intervening regions with very low incidences of methylation. To ascertain if such hot‐spot methylation is in fact a ubiquitous hallmark of MGMT‐silenced cells, we determined the methylation status of selected hot‐spot CpGs in an extensive panel of MGMT‐expressing and ‐silenced cell lines and xenografts. Using two simple and rapid bisulfite–polymerase chain reaction–based assays, we confirmed that in MGMT‐silenced cells, methylation occurred at these sites whereas it was essentially absent in MGMT‐expressing cells. Mol. Carcinog. 24:85–89, 1999. © 1999 Wiley‐Liss, Inc.