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- Title
Influence of promoter/enhancer region haplotypes on MGMT transcriptional regulation: a potential biomarker for human sensitivity to alkylating agents.
- Authors
Xu, Meixiang; Nekhayeva, Ilona; Cross, Courtney E.; Rondelli, Catherine M.; Wickliffe, Jeffrey K.; Abdel-Rahman, Sherif Z.
- Abstract
The current investigation is the first to define the haplotype structure of the promoter/enhancer region of the MGMT gene and to evaluate the functional significance of these haplotypes.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.
- Subjects
PROMOTERS (Genetics); GENE enhancers; HAPLOTYPES; GENETIC transcription regulation; BIOMARKERS; ALKYLATION; O6-Methylguanine-DNA Methyltransferase; METHYLTRANSFERASES
- Publication
Carcinogenesis, 2014, Vol 35, Issue 3, p564
- ISSN
0143-3334
- Publication type
Article