Identification of a single nucleotide polymorphism in the TATA box of the CYP2A6 gene: impairment of its promoter activity.
Human cytochrome P450 2A6 (CYP2A6) constitutes the major nicotine oxidase, and large interindividual differences are seen in the levels of this enzyme, to a great extent caused by the distribution of several different polymorphic gene variants mainly located in the open reading frame (ORF). In the present study, we report a common polymorphism located in the 5' flanking region of CYP2A6 affecting its expression. DHPLC analysis and complete sequence of the open reading frame of the gene from a Turkish individual revealed a -48T > G substitution disrupting the TATA box. Using dynamic allele-specific hybridization (DASH), genotyping of this novel variant (named CYP2A6*9) was carried out in 116 Swedish, 132 Turkish, and 102 Chinese subjects, and the allele frequencies were found to be 5.2, 7.2, and 15.7%, respectively. The significance of the polymorphism was investigated by the construction of luciferase reporter plasmids containing 135 or 500 bp of the 5'-upstream region of the gene transfected into human hepatoma B16A2 cells. The constructs carrying the -48T > G mutation were only expressed at about 50% of the wild-type alleles. It is concluded that the CYP2A6*9 allele might be one of the most common CYP2A6 variants in Caucasians that alters the levels of enzyme expression.
Pitarque
M
M
Institute of Environmental Medicine, Karolinska Institutet, Stockholm, 171 77, Sweden.
von Richter
O
O
Oke
B
B
Berkkan
H
H
Oscarson
M
M
Ingelman-Sundberg
M
M
D000483:Alleles; D001189:Aryl Hydrocarbon Hydroxylases; D044466:Asian People / Q000235:genetics; D002460:Cell Line; D002681:China / Q000208:ethnology; D002851:Chromatography, High Pressure Liquid; D065637:Cytochrome P-450 CYP2A6; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004252:DNA Mutational Analysis; D015870:Gene Expression / Q000502:physiology; D017930:Genes, Reporter; D005820:Genetic Testing; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009691:Nucleic Acid Denaturation; D009692:Nucleic Acid Heteroduplexes / Q000032:analysis / Q000235:genetics; D009693:Nucleic Acid Hybridization / Q000379:methods; D010088:Oxidoreductases / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000502:physiology*; D013548:Sweden / Q000208:ethnology; D016385:TATA Box / Q000235:genetics*; D014162:Transfection; D014421:Turkey / Q000208:ethnology; D044465:White People / Q000235:genetics
D009692:Nucleic Acid Heteroduplexes; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6; C034523:nicotine oxidase