Studies of the hormone-dependent expression of conalbumin gene

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Conalbumin, an egg white protein, is induced in the chick oviduct by the administration of estrogen. Steroid hormones including estrogen bind to specific receptors in target cells, then the steroid-receptor complexes exert the stimulation effects through their binding to nuclear chromatin. In this study, the role of nuclear histone acetylation was studied. Female chicks were stimulated for 14 to 19 days with estrogen, then oviducts were removed. Nuclear histone was acetylated by incubating the tissue with ^3H-sodium acetate. The release of acetylated histones from chick oviduct chromatin was analyzed by hydroxylapatite column chromatography. By raising of the NaCl concentration, acetylated histones were eluted from hydroxylapatite-bound chromatin depending on their release from nucleosomal DNA. Electrophoresis on acid-urea gel showed that hypoeracetylated forms of histone H4 were eluted at a lower NaCl concentration than non-acetylated or hypoacetylated H4, indicating that hyperacetylated H4 has decreased stability in nucleosomes. These data strongly suggest that histone acetylation has an important role on the gene expression in the chick oviduct.