Abu-Abed S S, Beckett B R, Chiba H, Chithalen J V, Jones G, Metzger D, Chambon P, Petkovich M
Cancer Research Laboratories, Queen's University, Kingston, Ontario, Canada.
J Biol Chem. 1998 Jan 23;273(4):2409-15. doi: 10.1074/jbc.273.4.2409.
We have cloned a mouse cDNA homolog of P450RAI, a cytochrome P450 belonging to a new family (CYP26), which has previously been isolated from zebrafish and human cDNAs and found to encode a retinoic acid-inducible retinoic acid hydroxylase activity. The cross-species conservation of the amino acid sequence is high, particularly between the mouse and the human enzymes, in which it is over 90%. Like its human and zibrafish counterparts, the mouse P450RAI cDNA catalyzes metabolism of retinoic acid into 4-OH-retinoic acid, 4-oxo-retinoic acid, 18-OH-retinoic acid, and unidentified water-soluble metabolites when transfected into COS-1 cells. Retinoic acid-inducible retinoic acid metabolism has previously been observed in F9 murine embryonal carcinoma cells and some derivatives lacking retinoid receptors. We were interested in determining whether P450RAI could be responsible for retinoic acid metabolism in F9 cells and in studying the effect of retinoid receptor ablation on P450RAI expression. In wild-type F9 cells and derivatives lacking RAR gamma, RAR alpha, and/or RXR alpha, we observed a direct relationship between the level of retinoic acid metabolic activity and retinoic acid-induced P450RAI mRNA. These experiments, as well as others using synthetic receptor subtype-specific retinoids, suggest that the RAR gamma and RXR alpha receptors mediate the effects of retinoic acid on the expression of the P450RAI gene.
我们克隆了P450RAI的小鼠cDNA同源物，P450RAI是一种属于新家族（CYP26）的细胞色素P450，此前已从斑马鱼和人cDNA中分离出来，并发现其编码一种视黄酸诱导的视黄酸羟化酶活性。氨基酸序列的跨物种保守性很高，尤其是在小鼠和人酶之间，超过了90%。与人类和斑马鱼的对应物一样，小鼠P450RAI cDNA转染到COS-1细胞后，催化视黄酸代谢为4-羟基视黄酸、4-氧代视黄酸、18-羟基视黄酸和未鉴定的水溶性代谢产物。视黄酸诱导的视黄酸代谢此前已在F9小鼠胚胎癌细胞和一些缺乏类视黄醇受体的衍生物中观察到。我们感兴趣的是确定P450RAI是否可能是F9细胞中视黄酸代谢的原因，并研究类视黄醇受体缺失对P450RAI表达的影响。在野生型F9细胞以及缺乏RARγ、RARα和/或RXRα的衍生物中，我们观察到视黄酸代谢活性水平与视黄酸诱导的P450RAI mRNA之间存在直接关系。这些实验以及其他使用合成受体亚型特异性类视黄醇的实验表明，RARγ和RXRα受体介导视黄酸对P450RAI基因表达的影响。
