Sueyoshi T, Kawamoto T, Zelko I, Honkakoski P, Negishi M
Pharmacogenetics Section, Laboratory of Reproductive and Developmental Toxicology, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
J Biol Chem. 1999 Mar 5;274(10):6043-6. doi: 10.1074/jbc.274.10.6043.
The endogenous CYP2B6 gene becomes phenobarbital (PB) inducible in androstenol-treated HepG2 cells either transiently or stably transfected with a nuclear receptor CAR expression vector. The PB induction mediated by CAR is regulated by a conserved 51-base pair element called PB-responsive enhancer module (PBREM) that has now been located between -1733 and -1683 bp in the gene's 5'-flanking region. An in vitro translated CAR acting as a retinoid X receptor alpha heterodimer binds directly to the two nuclear receptor sites NR1 and NR2 within PBREM. In a stably transfected HepG2 cell line, both PBREM and NR1 are activated by PB and PB-type compounds such as chlorinated pesticides, polychlorinated biphenyls and chlorpromazine. In addition to PBREM, CAR also transactivates the steroid/rifampicin-response element of the human CYP3A4 gene in HepG2 cells. Thus, activation of the repressed nuclear receptor CAR appears to be a versatile mediator that regulates PB induction of the CYP2B and other genes.
在用雄烯醇处理过的、瞬时或稳定转染了核受体CAR表达载体的HepG2细胞中，内源性CYP2B6基因可被苯巴比妥（PB）诱导。由CAR介导的PB诱导作用受一个名为PB反应增强子模块（PBREM）的51个碱基对的保守元件调控，该元件现已定位在该基因5'侧翼区的-1733至-1683 bp之间。作为视黄酸X受体α异二聚体的体外翻译的CAR直接与PBREM内的两个核受体位点NR1和NR2结合。在一个稳定转染的HepG2细胞系中，PBREM和NR1均被PB以及PB类化合物（如氯代农药、多氯联苯和氯丙嗪）激活。除PBREM外，CAR还可在HepG2细胞中转激活人CYP3A4基因的类固醇/利福平反应元件。因此，被抑制的核受体CAR的激活似乎是一种通用的介质，可调节CYP2B及其他基因的PB诱导作用。
