期刊
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH
卷 1593, 期 1, 页码 45-55出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0167-4889(02)00347-6
关键词
protein kinase; oncogene; phosphorylation; cell cycle inhibitor p21(Cip1/WAF1)
资金
- NIAID NIH HHS [T32-AI07025] Funding Source: Medline
- NIA NIH HHS [R01 AG16694] Funding Source: Medline
The serine/threonine kinase, Pim-1, appears to be involved in regulating proliferation, differentiation and cell survival of lymphoid and myeloid cells. In this study, we have found that amino acid residues 140-147 (RKRRQTSM) at the C-terminal end of p21(Cip1/WAF1), a cyclin-dependent kinase (CDK) inhibitor, constitute an ideal phosphorylation consensus sequence for Pim-1. We demonstrate that Pim-1 efficiently phosphorylates this peptide sequence as well as the p21 protein in vitro. We also demonstrate by pull-down assay and by immunoprecipitation that Pim-1 associates with p21. During phorbol ester-induced differentiation of U937 cells, both Pim-1 and p21 expression levels increase with Pim-1 levels increasing in both the nucleus and cytoplasm while p21 remains primarily cytoplasmic. Co-transfection of wild type p21 with wild type Pim-1 results in cytoplasmic localization of p21 while co-transfection of wild type p21 with kinase dead Pim-1 results in nuclear localization of p21. Consistent with the results from the phosphoamino acid assay, Pim-1 phosphorylates transfected p21 only on Thr(145) in p21-deficient human fibroblasts and this phosphorylation event results in the cytoplasmic localization of p21. These findings demonstrate that Pim-1 associates with and phosphorylates p21 in vivo, which influences the subcellular localization of p21. (C) 2002 Elsevier Science B.V. All rights reserved.
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