TY - JOUR
T1 - Influence of promoter/enhancer region haplotypes on MGMT transcriptional regulation
T2 - A potential biomarker for human sensitivity to alkylating agents
AU - Xu, Meixiang
AU - Nekhayeva, Ilona
AU - Cross, Courtney E.
AU - Rondelli, Catherine M.
AU - Wickliffe, Jeffrey K.
AU - Abdel-Rahman, Sherif Z.
N1 - Funding Information:
National Institutes of Health (R03 NS065392-01, T-32-ES007254 and F31-019053); National Institute of Environmental Health Sciences Center in Environmental Toxicology at the University of Texas Medical Branch (P30 ES006676); John Sealy Memorial Endowment fund for Biomedical Research; the Institute for Translational Sciences at the University of Texas Medical Branch; Clinical and Translational Science Award from the National Center for Research Resources (8UL1TR000071), now the National Center for Advancing Translational Sciences, National Institutes of Health.
PY - 2014/3
Y1 - 2014/3
N2 - The O6-methylguanine-DNA methyltransferase gene (MGMT) encodes the direct reversal DNA repair protein that removes alkyl adducts from the O6 position of guanine. Several single-nucleotide polymorphisms (SNPs) exist in the MGMT promoter/enhancer (P/E) region. However, the haplotype structure encompassing these SNPs and their functional/biological significance are currently unknown. We hypothesized that MGMT P/E haplotypes, rather than individual SNPs, alter MGMT transcription and can thus alter human sensitivity to alkylating agents. To identify the haplotype structure encompassing the MGMT P/E region SNPs, we sequenced 104 DNA samples from healthy individuals and inferred the haplotypes using the data generated. We identified eight SNPs in this region, namely T7C (rs180989103), T135G (rs1711646), G290A (rs61859810), C485A (rs1625649), C575A (rs113813075), G666A (rs34180180), C777A (rs34138162) and C1099T (rs16906252). Phylogenetics and Sequence Evolution analysis predicted 21 potential haplotypes that encompass these SNPs ranging in frequencies from 0.000048 to 0.39. Of these, 10 were identified in our study population as 20 paired haplotype combinations. To determine the functional significance of these haplotypes, luciferase reporter constructs representing these haplotypes were transfected into glioblastoma cells and their effect on MGMT promoter activity was determined. Compared with the most common (reference) haplotype 1, seven haplotypes significantly upregulated MGMT promoter activity (18-119% increase; P< 0.05), six significantly downregulated MGMT promoter activity (29-97% decrease; P < 0.05) and one haplotype had no effect. Mechanistic studies conducted support the conclusion that MGMT P/E haplotypes, rather than individual SNPs, differentially regulate MGMT transcription and could thus play a significant role in human sensitivity to environmental and therapeutic alkylating agents.
AB - The O6-methylguanine-DNA methyltransferase gene (MGMT) encodes the direct reversal DNA repair protein that removes alkyl adducts from the O6 position of guanine. Several single-nucleotide polymorphisms (SNPs) exist in the MGMT promoter/enhancer (P/E) region. However, the haplotype structure encompassing these SNPs and their functional/biological significance are currently unknown. We hypothesized that MGMT P/E haplotypes, rather than individual SNPs, alter MGMT transcription and can thus alter human sensitivity to alkylating agents. To identify the haplotype structure encompassing the MGMT P/E region SNPs, we sequenced 104 DNA samples from healthy individuals and inferred the haplotypes using the data generated. We identified eight SNPs in this region, namely T7C (rs180989103), T135G (rs1711646), G290A (rs61859810), C485A (rs1625649), C575A (rs113813075), G666A (rs34180180), C777A (rs34138162) and C1099T (rs16906252). Phylogenetics and Sequence Evolution analysis predicted 21 potential haplotypes that encompass these SNPs ranging in frequencies from 0.000048 to 0.39. Of these, 10 were identified in our study population as 20 paired haplotype combinations. To determine the functional significance of these haplotypes, luciferase reporter constructs representing these haplotypes were transfected into glioblastoma cells and their effect on MGMT promoter activity was determined. Compared with the most common (reference) haplotype 1, seven haplotypes significantly upregulated MGMT promoter activity (18-119% increase; P< 0.05), six significantly downregulated MGMT promoter activity (29-97% decrease; P < 0.05) and one haplotype had no effect. Mechanistic studies conducted support the conclusion that MGMT P/E haplotypes, rather than individual SNPs, differentially regulate MGMT transcription and could thus play a significant role in human sensitivity to environmental and therapeutic alkylating agents.
UR - http://www.scopus.com/inward/record.url?scp=84895831328&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84895831328&partnerID=8YFLogxK
U2 - 10.1093/carcin/bgt355
DO - 10.1093/carcin/bgt355
M3 - Article
C2 - 24163400
AN - SCOPUS:84895831328
SN - 0143-3334
VL - 35
SP - 564
EP - 571
JO - Carcinogenesis
JF - Carcinogenesis
IS - 3
M1 - bgt355
ER -