Role of the genetic polymorphisms in the 5'-flanking region for transcriptional regulation of the human CYP2E1 gene.
BACKGROUND
The human cytochrome P-4502E1 (CYP2E1) has been known to be that are associated with alcohol-related diseases and various cancers. Difference in susceptibility in enzyme induction of the CYP2E1 by environmental factors such as ethanol may be associated with the risk of these diseases. In the 5'-flanking region of the human CYP2E1 gene, there were tandem repeat polymorphism (CYP2E1*1C*,1D) and RsaI polymorphism (CYP2E1*5A*,5B), which have been reported to be related to these diseases. Thus, we focused relationship between these polymorphisms and transcriptional regulation. The aim of this study was to determine the role of these polymorphisms for the transcriptional regulation of the human CYP2E1 gene in general transcription and during enzyme induction.


METHODS
To determine the role of these polymorphisms, various constructs of the 5'-flanking region of the human CYP2E1 gene were prepared and transfected into HeLa cells and HepG2 cells treated or not with pyrazine, a well-known CYP2E1 inducer.


RESULTS
The transcriptional activity of CYP2E1*1D was higher than that of CYP2E1*1C in HeLa cells. The -1,306 base pairs (bp) construct (-1,306 to +9) increased transcriptional activity compared with the 2.5 kb full-length construct. The suppressive effect of transcriptional activity by deletion of the region including CYP2E1*1C was greater than that by CYP2E1*1D in HeLa cells. The -580 bp construct (-580 to +9) decreased transcriptional activity compared with the -1,306 bp construct. The -1,306 bp construct also showed a similar tendency during pyrazine treatment.


CONCLUSIONS
The region including the tandem repeat polymorphism was suggested to regulate transcription suppressively. Besides, it was speculated that the transcriptional activity of CYP2E1*1D was higher than that of CYP2E1*1C because transcriptional suppression of CYP2E1*1D was weaker than that of CYP2E1*1C. Also, it was confirmed that the region including RsaI polymorphism was associated with the promotion of transcription.
Uchimoto
Takayuki
T
Department of Molecular Diagnosis (F8), Graduate School of Medicine, Chiba University, Chiba, Japan.
Itoga
Sakae
S
Nezu
Masahiko
M
Sunaga
Masahiko
M
Tomonaga
Takeshi
T
Nomura
Fumio
F
D024506:5' Flanking Region / Q000235:genetics*; D045744:Cell Line, Tumor; D019392:Cytochrome P-450 CYP2E1 / Q000235:genetics*; D004790:Enzyme Induction; D006367:HeLa Cells; D006801:Humans; D011110:Polymorphism, Genetic / Q000235:genetics*; D020080:Tandem Repeat Sequences / Q000235:genetics*; D014162:Transfection
D019392:Cytochrome P-450 CYP2E1