CpG methylation of the mouse CYP1A2 promoter.
Cytochrome P450 1A2 (CYP1A2) is a xenobiotic metabolizing enzyme that is tissue-specifically regulated in the mammalian liver by arylhydrocarbon receptor (AhR)-dependent and -independent pathways. In this study, CpG methylation of the CYP1A2 promoter was analyzed in mouse tissues and liver-derived cells. Compared to lung and kidney, the CYP1A2 promoter is undermethylated in the liver in a promoter domain-specific manner. The CYP1A2 promoter showed a similar methylation pattern in wild-type and AhR-null liver. At birth, the promoter was hypermethylated and CYP1A2 was negligibly expressed in the liver. However, CYP1A2 expression increased following birth, coincident with the demethylation of the promoter. In hepatoma Hepa1c1c7 cells not expressing CYP1A2, the promoter was hypermethylated at specific CpG sites. In isolated hepatocytes, CYP1A2 expression declined over time and the degree of CYP1A2 methylation increased, albeit only after a delay. Exposure to 5-aza-2'-deoxycytidine did not induce CYP1A2 in Hepa1c1c7 cells and hepatocytes. Taken together, our findings suggest that CpG methylation is involved in the tissue-specific and developmental regulation of CYP1A2, but the de novo methylation of the CYP1A2 promoter is induced by the silent state of the gene rather than causing it.
College of Veterinary Medicine, Seoul National University, San 56-1, Sinlimdong, Kwanakgu, Seoul 151-742, South Korea.
Bowhan
B
Jin
Duk Woong
DW
Park
Ki-Whan
KW
Nam
Goo Taeg
GT
Oh
Yong-Soon
YS
Lee
Doug-Young
DY
Ryu
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D019388:Cytochrome P-450 CYP1A2 / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D022781:Hepatocytes; D007668:Kidney; D008099:Liver; D008113:Liver Neoplasms / Q000473:pathology; D008168:Lung; D051379:Mice; D008810:Mice, Inbred C57BL; D011401:Promoter Regions, Genetic; D014407:Tumor Cells, Cultured / Q000473:pathology
D019388:Cytochrome P-450 CYP1A2