title: Time-dependent interaction between differentiated embryo chondrocyte-2 and CCAAT/enhancer-binding protein α underlies the circadian expression of CYP2D6 in serum-shocked HepG2 cells.
abstract: Differentiated embryo chondrocyte-2 (DEC2), also known as bHLHE41 or Sharp1, is a pleiotropic transcription repressor that controls the expression of genes involved in cellular differentiation, hypoxia responses, apoptosis, and circadian rhythm regulation. Although a previous study demonstrated that DEC2 participates in the circadian control of hepatic metabolism by regulating the expression of cytochrome P450, the molecular mechanism is not fully understood. We reported previously that brief exposure of HepG2 cells to 50% serum resulted in 24-h oscillation in the expression of CYP3A4 as well as circadian clock genes. In this study, we found that the expression of CYP2D6, a major drug-metabolizing enzyme in humans, also exhibited a significant oscillation in serum-shocked HepG2 cells. DEC2 interacted with CCAAT/enhancer-binding protein (C/EBPα), accompanied by formation of a complex with histone deacetylase-1, which suppressed the transcriptional activity of C/EBPα to induce the expression of CYP2D6. The oscillation in the protein levels of DEC2 in serum-shocked HepG2 cells was nearly antiphase to that in the mRNA levels of CYP2D6. Transfection of cells with small interfering RNA against DEC2 decreased the amplitude of CYP2D6 mRNA oscillation in serum-shocked cells. These results suggest that DEC2 periodically represses the promoter activity of CYP2D6, resulting in its circadian expression in serum-shocked cells. DEC2 seems to constitute a molecular link through which output components from the circadian clock are associated with the time-dependent expression of hepatic drug-metabolizing enzyme.
authors.affiliation: Department of Pharmaceutics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Matsunaga
authors.forename: Miki
authors.initials: M
authors.lastname: Inoue
authors.forename: Naoki
authors.initials: N
authors.lastname: Kusunose
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kakimoto
authors.forename: Kengo
authors.initials: K
authors.lastname: Hamamura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Hanada
authors.forename: Ayumi
authors.initials: A
authors.lastname: Toi
authors.forename: Yuji
authors.initials: Y
authors.lastname: Yoshiyama
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Sato
authors.forename: Katsumi
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Satoru
authors.initials: S
authors.lastname: Koyanagi
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Ohdo
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology*; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000502:physiology*; D056926:CLOCK Proteins / Q000502:physiology; D002940:Circadian Rhythm; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics*; D056945:Hep G2 Cells; D051557:Hepatocyte Nuclear Factor 4 / Q000502:physiology; D006801:Humans; D012333:RNA, Messenger / Q000032:analysis; D044967:Serum; D013997:Time Factors
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D022763:CCAAT-Enhancer-Binding Protein-alpha; D056926:CLOCK Proteins; D019389:Cytochrome P-450 CYP2D6; D051557:Hepatocyte Nuclear Factor 4; D012333:RNA, Messenger; C422085:BHLHE41 protein, human; C496592:HNF4A protein, human; C538943:CLOCK protein, human