期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1974
卷号：71
期号：6
页码：2290-2294
DOI：10.1073/pnas.71.6.2290
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The porphyrin-heme pathway is controlled in the liver at the level of the mitochondrial enzyme {delta}-aminolevulinate synthase (EC 2.3.1.37 ), a protein inducible in cultured avian hepatocytes by a variety of chemicals including certain 5{beta}-metabolites of steroid hormones. The great sensitivity of the induction process to inhibition by agents known to block transcriptional activity of genetic material suggests that some control mechanism may be operating at this level to regulate the formation of the enzyme. We report here enhancement of nuclear RNA synthesis and of Mn2+-(NH4)2SO4-stimulated DNA-dependent RNA polymerase (EC 2.7.7.6 ) activities by the 5{beta}-steroid metabolite, 3[α]-hydroxy-5{beta}-androstan-17-one (etiocholanolone), in cultured avian hepatocytes during induction of the enzyme. These changes were demonstrated in the G1 phase of the hepatocyte cell cycle at a time when DNA synthesis is constant. Our findings support the view that one of the early steps in the process of induction of {delta}-aminolevulinate synthase by steroid metabolites requires new RNA synthesis, very probably messenger RNA, suggesting a 5{beta}-steroid transcriptional control mechanism for induction of this protein.
关键词：3α-hydroxy-5β-androstan-17-one and 2-allyl-2-isopropylacetamide action ; porphyrin-heme pathway ; RNA polymerases ; regulation ; protein synthesis
