title: Progesterone-binding components of chick oviduct. In vitro effect of receptor subunits on gene transcription.
abstract: We have studied chick oviduct progesterone receptor subunits and their effect on RNA transcription in oviduct chromatin. Initiation of RNA chain synthesis was measured by the rifampicin-challenge assay. Progesterone receptor subunits A and B were purified 200-fold by sequential chromatography on phosphocellulose, DEAE-cellulose, and hydroxylapatite. The subunits could be recombined to form the 6S receptor A-B dimer initially present in chick oviduct homogenates. The intact 6 S receptor dimer preparation increased transcription of oviduct chromatin by 40 to 60%. This increase corresponds to the creation of 5,800 new initiation sites per haploid cellular equivalent of DNA as chromatin. The increased chromatin transcription which resulted was half-maximal at a receptor concentration of about 5 x 10(-9) M. Preparations from other tissues which were devoid of progesterone-binding activity or oviduct preparations lacking progesterone did not stimulate rifampicin-resistant RNA synthesis. The oviduct receptor fraction contained no detectable glucocorticoid, androgen, or estrogen receptors. When isolated B subunits alone were incubated with chromatin, no transcriptional increase was detectable. Isolated A subunits increased chromatin transcription, but only at concentration approximately 10-fold higher than required of intact dimer. These observations suggest that the 6 S receptor dimer is the functional species in chromatin transcription in vivo; two hormones are required per dimer, one on each subunit. Since subunit A binds DNA and has stimulatory activity , a dimer dissociation at acceptor sites is postulated, liberating A subunits which stimulate RNA chain initiation sites.
mesh_terms: D000818:Animals; D002645:Chickens; D002843:Chromatin / Q000187:drug effects / Q000378:metabolism; D005260:Female; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D008954:Models, Biological; D009124:Muscle Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009994:Osmolar Concentration; D010057:Oviducts / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011374:Progesterone / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000187:drug effects; D012293:Rifampin / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D002843:Chromatin; D009124:Muscle Proteins; D011956:Receptors, Cell Surface; D008345:Manganese; D011374:Progesterone; D011189:Potassium Chloride; D012293:Rifampin