title: Transcriptional regulation of chicken cytochrome P450 2D49 basal expression by CCAAT/enhancer-binding protein α and hepatocyte nuclear factor 4α.
abstract: Chicken cytochrome P450 (CYP)2D49 is structurally and functionally related to human CYP2D6, which is an important drug-metabolizing enzyme. To date, little is known about the transcriptional regulation of this cytochrome. Through deletion analysis of the CYP2D49 promoter, we identified two putative degenerate CCAAT/enhancer-binding protein (C/EBP)-binding sites and an imperfect DR1 element (the site contains direct repeats of the hexamer AGGTCA separated by a one-nucleotide spacer motif) within regions -296/-274, -274/-226, and -226/-183, respectively, which may play critical roles in the transcriptional activation of the CYP2D49 gene. Electrophoretic mobility shift assays and chromatin immunoprecipitation assays showed that the putative C/EBP boxes and DR1 element in the CYP2D49 promoter are functional motifs that bind to C/EBPα and hepatocyte nuclear factor 4α (HNF4α), respectively. Furthermore, we studied the functional importance and relationships of these transcription factor-binding sites by examining the effects of mutation and deletion of these regions on promoter activity. These studies revealed that the two C/EBP-binding sites show a compensatory relationship and work cooperatively with the DR1 element to modulate the transcription of CYP2D49. The results of overexpressing C/EBPα and HNF4α in culture cells further confirmed that both C/EBPα and HNF4α contribute significantly to sustaining a high level of CYP2D49 transcription. In conclusion, the data indicate that the constitutive hepatic expression of CYP2D49 is governed by both C/EBPα and HNF4α. Further studies will be required to fully characterize the molecular mechanisms that modulate CYP2D49 expression.
authors.affiliation: Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.
authors.forename: Shulin
authors.initials: S
authors.lastname: Tang
authors.affiliation: Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.
authors.forename: Linfeng
authors.initials: L
authors.lastname: Dong
authors.affiliation: Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.
authors.forename: Qingmei
authors.initials: Q
authors.lastname: Chen
authors.affiliation: Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.affiliation: Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Jiang
authors.affiliation: Guangdong Provincial Key Laboratory of Protein Function and Regulation in Agricultural Organisms, College of Life Sciences, South China Agricultural University, Guangzhou, China.
authors.forename: Yiqun
authors.initials: Y
authors.lastname: Deng
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism*; D002645:Chickens; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D051557:Hepatocyte Nuclear Factor 4 / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D050436:Regulatory Elements, Transcriptional; D017384:Sequence Deletion; D015533:Transcriptional Activation
chemical_list: D030161:Avian Proteins; D022763:CCAAT-Enhancer-Binding Protein-alpha; D051557:Hepatocyte Nuclear Factor 4; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D019389:Cytochrome P-450 CYP2D6
keywords: CCAAT/enhancer-binding protein α (C/EBPα); chicken; cytochrome P450 (CYP) 2D49; hepatocyte nuclear factor 4α (HNF4α); transcriptional regulation