Mechanism of Action of Gonadotropin. IV. Cyclic Adenosine Monophosphate-Dependent Translocation of Ovarian Cytoplasmic Cyclic Adenosine Monophosphate-Binding Protein and Protein Kinase to Nuclear Acceptor Sites¹

The interaction in vitro of cyclic [3H]AMP and a partially purified cyclic [3H] AMP-binding protein preparation from calf ovary cytosol with nuclei and chromatin of calf ovaries was investigated. Cyclic [3H]AMP, complexed with a calf ovary cytosol protein (the cyclic AMP-binding protein), binds to ovary nuclei and chromatin, whereas free cyclic [3H]AMP does not bind. Concomitantly with the nuclear association of cyclic [3H]AMP-binding protein, cyclic AMP-independent protein kinase activity in nuclei and chromatin incubated with a calf ovary cyclic [3H]AMP-binding protein preparation is significantly enhanced. The increase of nuclear protein kinase activity is dependent upon the presence of cyclic AMP complexed to ovary cytosol protein, and neither free cyclic AMP nor cyclic AMP-free binding protein stimulate endogenous nuclear protein kinase activity in ovary nuclei or chromatin. The association in vitro of cyclic [3H]AMP-binding protein with ovary chromatin and nuclei as well as the concomitant increase of nuclear protein kinase activity is sensitive to conditions of temperature and ionic strength. Cyclic AMP-binding protein and protein kinase can be reextracted from nuclei by treatment with 0.3M NaCl. Sucrose density gradient analysis bf cytosol protein kinase and cyclic [3H]AMP-binding protein before their binding to nuclei and after their extraction from nuclei with 0.3M NaCl reveals a significant change of their sedimentation coefficients. Furthermore, the binding of ovary cyclic [3H]AMP-binding protein and concomitant increase of nuclear protein kinase activity are more extensive in ovary nuclei and chromatin than in nuclei and chromatin from calf adrenal, liver, and uterus indicating a tissue-specificity of binding of cyclic [3H]AMP-binding protein and increase of nuclear protein kinase activity. The results appear to indicate a cyclic AMP-dependent translocation of cytoplasmic cyclic AMP-binding protein and possibly of cytoplasmic protein kinase to nuclear acceptor sites. The precise biological significance of this nuclear translocation of the cyclic AMP-binding protein complex and concomitant increase of nuclear protein kinase activity remains to be defined. (Endocrinology94: 168, 1974)