Progesterone-binding protein of chick oviduct. VI. Interaction of purified progesterone-receptor components with nuclear constituents.

Abstract Components A and B of the chick oviduct progesterone-binding protein system have been prepared by chromatography on DEAE-cellulose. Both components are shown to bind [3H]progesterone in vivo and to accumulate in oviduct nuclei in vitro. Neither component preparation contains detectable enzymatic activity for metabolizing progesterone in vitro. Each component can enter nuclei separately where both are strongly retained bound to nuclear chromatin. In vitro assays for the interaction of the components with DNA and chromatin acidic proteins were used to study binding specificity of the components. Component A binds to DNA from several sources but Component B does not bind to DNA. Conversely, Component B binds to purified oviduct chromatin and retains target organ specificity, but Component A does not bind to purified chromatin. The two types of binding activity characteristic of crude cytosol progesterone receptor, namely, the association with DNA and with target cell chromatin proteins have thus been resolved and shown to reside in receptor Components A and B, respectively.