title: Nuclear localization and regulation of erk- and rsk-encoded protein kinases.
abstract: We demonstrate that members of the erk-encoded family of mitogen-activated protein (MAP) kinases (pp44/42mapk/erk) and members of the rsk-encoded protein kinases (RSKs or pp90rsk) are present in the cytoplasm and nucleus of HeLa cells. Addition of growth factors to serum-deprived cells results in increased tyrosine and threonine phosphorylation and in the activation of cytosolic and nuclear MAP kinases. Activated MAP kinases then phosphorylate (serine/threonine) and activate RSKs. Concurrently, a fraction of the activated MAP kinases and RSKs enter the nucleus. In addition, a distinct growth-regulated RSK-kinase activity (an enzyme[s] that phosphorylates recombinant RSK in vitro and that may be another member of the erk-encoded family of MAP kinases) was found associated with a postnuclear membrane fraction. Regulation of nuclear MAP kinase and RSK activities by growth factors and phorbol ester is coordinate with immediate-early gene expression. Indeed, in vitro, MAP kinase and/or RSK phosphorylates histone H3 and the recombinant c-Fos and c-Jun polypeptides, transcription factors phosphorylated in a variety of cells in response to growth stimuli. These in vitro studies raise the possibility that the MAP kinase/RSK signal transduction pathway represents a protein-Tyr/Ser/Thr phosphorylation cascade with the spatial distribution and temporal regulation that can account for the rapid transmission of growth-regulating information from the membrane, through the cytoplasm, and to the nucleus.
authors.affiliation: Department of Cellular and Molecular Physiology, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: R H
authors.initials: RH
authors.lastname: Chen
authors.forename: C
authors.initials: C
authors.lastname: Sarnecki
authors.forename: J
authors.initials: J
authors.lastname: Blenis
mesh_terms: D000595:Amino Acid Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002455:Cell Division; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D015398:Signal Transduction; D013379:Substrate Specificity
chemical_list: D011506:Proteins; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; C069329:RPS6KA1 protein, human; D038744:Ribosomal Protein S6 Kinases, 90-kDa; C069330:ribosomal protein S6 kinase, 90kDa, polypeptide 3; D017871:Calcium-Calmodulin-Dependent Protein Kinases