Open AccessThe 25-kDa FK506-binding protein is localized in the nucleus and associates with casein kinase II and nucleolin.
Author(s) -
Yong Jiu Jin,
Steven J. Burakoff
Publication year - 1993
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.90.16.7769
Subject(s) - casein kinase 2 , casein kinase 1 , nucleolin , casein kinase 2, alpha 1 , biochemistry , biology , phosphorylation , kinase , microbiology and biotechnology , protein kinase a , mitogen activated protein kinase kinase , cyclin dependent kinase 2 , chemistry , cytoplasm , nucleolus
FK506-binding proteins (FKBPs) have been identified as the cellular receptors of the immunosuppressive drugs FK506 and rapamycin. Recently, we cloned a 25-kDa FKBP family member (FKBP25) and found that FKBP25 contains a nuclear localization sequence and several potential casein kinase II phosphorylation sites. It has been previously shown that phosphorylation of proteins by casein kinase II can enhance their nuclear localization. Here we demonstrate that FKBP25 is localized to the nucleus and that a glutathione S-transferase fusion protein of FKBP25 (GST-FKBP25) can be phosphorylated by casein kinase II. Also a stable FKBP25/casein kinase II complex was formed when the GST-FKBP25 fusion protein was incubated either with purified casein kinase II or with cell lysates. Furthermore, when GST-FKBP25 was incubated with nuclear lysates, nucleolin, a major nuclear substrate of casein kinase II, was found associated with the GST-FKBP25/casein kinase II complex. Casein kinase II phosphorylation of several cytosolic and nuclear substrates, including nucleolin, appears to be important for the regulation of cell growth. The interaction of FKBP25 with casein kinase II may regulate these functions.