Extracellular signal-regulated kinase 2-dependent phosphorylation induces cytoplasmic localization and degradation of p21Cip1.
p21(Cip1) is an inhibitor of cell cycle progression that promotes G(1)-phase arrest by direct binding to cyclin-dependent kinase and proliferating cell nuclear antigen. Here we demonstrate that mitogenic stimuli, such as epidermal growth factor treatment and oncogenic Ras transformation, induce p21(Cip1) downregulation at the posttranslational level. This downregulation requires the sustained activation of extracellular signal-regulated kinase 2 (ERK2), which directly interacts with and phosphorylates p21(Cip1), promoting p21(Cip1) nucleocytoplasmic translocation and ubiquitin-dependent degradation, thereby resulting in cell cycle progression. ERK1 is not likely involved in this process. Phosphopeptide analysis of in vitro ERK2-phosphorylated p21(Cip1) revealed two phosphorylation sites, Thr57 and Ser130. Double mutation of these sites abolished ERK2-mediated p21(Cip1) translocation and degradation, thereby impairing ERK2-dependent cell cycle progression at the G(1)/S transition. These results indicate that ERK2 activation transduces mitogenic signals, at least in part, by downregulating the cell cycle inhibitory protein p21(Cip1).
Laboratory of Cell Signaling, Aging Research Center, Korea Research Institute of Bioscience and Biotechnology, 52 Oun-Dong, Yusong, Daejeon 305-333, South Korea.
Chae Young
CY
Hwang
Cheolju
C
Lee
Ki-Sun
KS
Kwon
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002453:Cell Cycle; D002460:Cell Line; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D015536:Down-Regulation; D004789:Enzyme Activation; D011905:Genes, ras; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D041681:NIH 3T3 Cells; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D013379:Substrate Specificity; D025801:Ubiquitin / Q000378:metabolism
C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D034741:RNA, Small Interfering; D025801:Ubiquitin; D019950:Mitogen-Activated Protein Kinase 1; D046988:Proteasome Endopeptidase Complex