Einck L, Fagan J, Bustin M
Biochemistry. 1985 Sep 10;24(19):5269-75. doi: 10.1021/bi00340a047.
Plasmids carrying fragments of a cytochrome P-450 gene, inducible by 3-methylcholanthrene, were used to study the chromatin structure of this gene in the liver of normal and carcinogen-treated rats. Digestion with micrococcal nuclease revealed that the gene is not present in the typical 200 base pair nucleosomal structure. By use of indirect end-label hybridization, four DNase I hypersensitive sites were mapped in the 5'-terminal region of the gene. An S1 nuclease sensitive site is located close to a DNase I site. Gene induction by treatment with 3-methylcholanthrene does not result in detectable changes in the DNase I hypersensitive sites. Rat thymus chromatin does not contain DNase I hypersensitive sites in the P-450 gene, suggesting that in the liver the chromatin structure is altered so as to allow tissue-specific expression of the gene. This paper is the first study on the chromatin structure of a gene coding for a member of the cytochrome P-450 family of enzymes. The implications of our results to the understanding of gene regulation of the P-450 genes are discussed.
携带细胞色素P-450基因片段（可被3-甲基胆蒽诱导）的质粒，被用于研究该基因在正常大鼠和经致癌物处理的大鼠肝脏中的染色质结构。用微球菌核酸酶消化显示，该基因不存在于典型的200碱基对核小体结构中。通过间接末端标记杂交，在该基因的5'端区域定位了四个脱氧核糖核酸酶I超敏位点。一个S1核酸酶敏感位点位于靠近脱氧核糖核酸酶I位点处。用3-甲基胆蒽处理诱导基因表达，并未导致脱氧核糖核酸酶I超敏位点出现可检测到的变化。大鼠胸腺染色质在P-450基因中不含有脱氧核糖核酸酶I超敏位点，这表明在肝脏中染色质结构发生了改变，从而允许该基因进行组织特异性表达。本文是对编码细胞色素P-450酶家族成员的基因染色质结构的首次研究。讨论了我们的结果对理解P-450基因调控的意义。
