title: CDK-mediated regulation of cell functions via c-Jun phosphorylation and AP-1 activation.
abstract: Cyclin-dependent kinases (CDKs) and their targets have been primarily associated with regulation of cell-cycle progression. Here we identify c-Jun, a transcription factor involved in the regulation of a broad spectrum of cellular functions, as a newly recognized CDK substrate. Using immune cells from mouse and human, and several complementary in vitro and in vivo approaches including dominant negative protein expression, pharmacologic inhibitors, kinase assays and CDK4 deficient cells, we demonstrate the ability of CDK4 to phosphorylate c-Jun. Additionally, the activity of AP-1, a ubiquitous transcription factor containing phosphorylated c-Jun as a subunit, was inhibited by abrogating CDK4. Surprisingly, the regulation of c-Jun phosphorylation by CDK4 occurred in non-dividing cells, indicating that this pathway is utilized for cell functions that are independent of proliferation. Our studies identify a new substrate for CDK4 and suggest a mechanism by which CDKs can regulate multiple cellular activation functions, not all of which are directly associated with cell cycle progression. These findings point to additional roles of CDKs in cell signaling and reveal potential implications for therapeutic manipulations of this kinase pathway.
authors.affiliation: Department of Microbiology, The University of Iowa, Iowa City, Iowa, United States of America.
authors.forename: Tony J
authors.initials: TJ
authors.lastname: Vanden Bush
authors.forename: Gail A
authors.initials: GA
authors.lastname: Bishop
mesh_terms: D000818:Animals; D019013:CD40 Antigens / Q000378:metabolism; D002453:Cell Cycle; D049109:Cell Proliferation; D051358:Cyclin-Dependent Kinase 4 / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D006801:Humans; D007107:Immune System; D015850:Interleukin-6 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D051199:Toll-Like Receptor 7 / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism*
chemical_list: D019013:CD40 Antigens; D015850:Interleukin-6; D008562:Membrane Glycoproteins; C495348:TLR7 protein, human; C477038:Tlr7 protein, mouse; D051199:Toll-Like Receptor 7; D018808:Transcription Factor AP-1; C495900:CDK4 protein, human; C495902:Cdk4 protein, mouse; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D048031:JNK Mitogen-Activated Protein Kinases