title: c-Jun regulates cell cycle progression and apoptosis by distinct mechanisms.
abstract: c-Jun is a component of the transcription factor AP-1, which is activated by a wide variety of extracellular stimuli. The regulation of c-Jun is complex and involves both increases in the levels of c-Jun protein as well as phosphorylation of specific serines (63 and 73) by Jun N-terminal kinase (JNK). We have used fibroblasts derived from c-Jun null embryos to define the role of c-Jun in two separate processes: cell growth and apoptosis. We show that in fibroblasts, c-Jun is required for progression through the G1 phase of the cell cycle; c-Jun-mediated G1 progression occurs by a mechanism that involves direct transcriptional control of the cyclin D1 gene, establishing a molecular link between growth factor signaling and cell cycle regulators. In addition, c-Jun protects cells from UV-induced cell death and cooperates with NF-kappaB to prevent apoptosis induced by tumor necrosis factor alpha (TNFalpha). c-Jun mediated G1 progression is independent of phosphorylation of serines 63/73; however, protection from apoptosis in response to UV, a potent inducer of JNK/SAP kinase activity, requires serines 63/73. The results reveal critical roles for c-Jun in two different cellular processes and show that different extracellular stimuli can target c-Jun by distinct biochemical mechanisms.
authors.affiliation: Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
authors.forename: R
authors.initials: R
authors.lastname: Wisdom
authors.forename: R S
authors.initials: RS
authors.lastname: Johnson
authors.forename: C
authors.initials: C
authors.lastname: Moore
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D016758:Genes, jun; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000502:physiology*; D014466:Ultraviolet Rays
chemical_list: D016755:Proto-Oncogene Proteins c-jun; D004247:DNA; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases