Abstract
p53 limits the proliferation of primary diploid fibroblasts by inducing a state of growth arrest named replicative senescence - a process which protects against oncogenic transformation and requires integrity of the p53 tumour suppressor pathway. However, little is known about the downstream target genes of p53 in this growth-limiting response. Here, we report that suppression of the p53 target gene encoding plasminogen activator inhibitor-1 (PAI-1) by RNA interference (RNAi) leads to escape from replicative senescence both in primary mouse embryo fibroblasts and primary human BJ fibroblasts. PAI-1 knockdown results in sustained activation of the PI(3)K-PKB-GSK3beta pathway and nuclear retention of cyclin D1, consistent with a role for PAI-1 in regulating growth factor signalling. In agreement with this, we find that the PI(3)K-PKB-GSK3beta-cyclin D1 pathway is also causally involved in cellular senescence. Conversely, ectopic expression of PAI-1 in proliferating p53-deficient murine or human fibroblasts induces a phenotype displaying all the hallmarks of replicative senescence. Our data indicate that PAI-1 is not merely a marker of senescence, but is both necessary and sufficient for the induction of replicative senescence downstream of p53.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Blotting, Western
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Cell Proliferation / drug effects
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Cells, Cultured
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Cellular Senescence / genetics
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Cellular Senescence / physiology*
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Cisplatin / pharmacology
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Cyclin-Dependent Kinase 4 / metabolism
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Cyclin-Dependent Kinase Inhibitor p16
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Cyclin-Dependent Kinase Inhibitor p21 / metabolism
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DNA Damage
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Embryo, Mammalian / cytology
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Fibroblasts / cytology
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Fibroblasts / drug effects
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Fibroblasts / metabolism
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Glycogen Synthase Kinase 3 / metabolism
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Glycogen Synthase Kinase 3 beta
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Humans
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Mice
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Microscopy, Fluorescence
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Mutation / genetics
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NIH 3T3 Cells
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Phosphatidylinositol 3-Kinases / metabolism
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Plasminogen Activator Inhibitor 1 / genetics
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Plasminogen Activator Inhibitor 1 / physiology*
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Proto-Oncogene Proteins c-akt / metabolism
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RNA Interference
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Tumor Suppressor Protein p14ARF / metabolism
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Tumor Suppressor Protein p53 / genetics
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Tumor Suppressor Protein p53 / physiology*
Substances
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Cdkn2a protein, mouse
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Cyclin-Dependent Kinase Inhibitor p16
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Cyclin-Dependent Kinase Inhibitor p21
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Plasminogen Activator Inhibitor 1
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Tumor Suppressor Protein p14ARF
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Tumor Suppressor Protein p53
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Phosphatidylinositol 3-Kinases
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GSK3B protein, human
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Glycogen Synthase Kinase 3 beta
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Gsk3b protein, mouse
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Proto-Oncogene Proteins c-akt
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Cyclin-Dependent Kinase 4
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Glycogen Synthase Kinase 3
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Cisplatin