TY - JOUR
T1 - Human microsomal epoxide hydrolase
T2 - 5'-Flanking region genetic polymorphisms
AU - Raaka, Stuart
AU - Hassett, Christopher
AU - Omiecinski, Curtis J.
PY - 1998/3
Y1 - 1998/3
N2 - Microsomal epoxide hydrolase (mEH) catalyses the hydrolysis of xenobiotic epoxides, including various epoxide derivatives of the procarcinogenic polyaromatic hydrocarbons. Levels of mEH enzymatic activity among different cell types and between individuals within the population vary considerably. Genetic polymorphisms within the structural region of the human mEH gene exist and appear to contribute to the population variance in functional expression. In this study, we used single strand conformational polymorphism analysis and direct DNA sequencing approaches to identify seven additional polymorphic sites within the upstream region of the mEH gene, spanning 743 to +185 bp, relative to the transcription initiation site. Allelic frequencies and linkages of the polymorphic nucleotides were determined in 51 individuals using restriction fragment length polymorphism or competitive oligonucleotide priming assays. To determine the functional significance of the individual nucleotide substitutions, DNA fragments representing the variant alleles were cloned into the heterologous pBRAMScat2 reporter vector, transfected into HepG2 cells and assessed for reporter gene expression. Results indicated that certain of these polymorphic loci might differentially regulate transcription, with the maximum contribution of any of the variants modifying levels of reporter gene activity by ~ 30%. These observations establish that genetic variation in the 5' flanking sequence of mEH gene is likely an additional contributing factor to the range of functional mEH expression existing in human populations.
AB - Microsomal epoxide hydrolase (mEH) catalyses the hydrolysis of xenobiotic epoxides, including various epoxide derivatives of the procarcinogenic polyaromatic hydrocarbons. Levels of mEH enzymatic activity among different cell types and between individuals within the population vary considerably. Genetic polymorphisms within the structural region of the human mEH gene exist and appear to contribute to the population variance in functional expression. In this study, we used single strand conformational polymorphism analysis and direct DNA sequencing approaches to identify seven additional polymorphic sites within the upstream region of the mEH gene, spanning 743 to +185 bp, relative to the transcription initiation site. Allelic frequencies and linkages of the polymorphic nucleotides were determined in 51 individuals using restriction fragment length polymorphism or competitive oligonucleotide priming assays. To determine the functional significance of the individual nucleotide substitutions, DNA fragments representing the variant alleles were cloned into the heterologous pBRAMScat2 reporter vector, transfected into HepG2 cells and assessed for reporter gene expression. Results indicated that certain of these polymorphic loci might differentially regulate transcription, with the maximum contribution of any of the variants modifying levels of reporter gene activity by ~ 30%. These observations establish that genetic variation in the 5' flanking sequence of mEH gene is likely an additional contributing factor to the range of functional mEH expression existing in human populations.
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U2 - 10.1093/carcin/19.3.387
DO - 10.1093/carcin/19.3.387
M3 - Article
C2 - 9525271
AN - SCOPUS:0031927837
SN - 0143-3334
VL - 19
SP - 387
EP - 393
JO - Carcinogenesis
JF - Carcinogenesis
IS - 3
ER -