Abstract
Recently Gadd45, a p53-regulated stress protein, has been implicated in the activation of a G2/M checkpoint after damage by UV radiation and alkylating agents. While inhibitory phosphorylation of Cdc2 and suppression of cyclin B1 levels are known to be involved in G2 delays after genotoxic stress, Gadd45 has now been found to directly inhibit the activity of Cdc2/Cyclin B1 complex, while it had no appreciable effect on Cdk2/ Cyclin E activity even at very high levels of Gadd45. In contrast, p21CiP1/Waf1 is an universal cdk/cyclin inhibitor and inhibited both of the cyclin complexes tested here. Gadd45 was also able to physically interact with Cdc2, but not Cyclin B1. Addition of Gadd45 to immunoprecipitated Cdc2/Cyclin B1 in vitro led to a dissociation of this complex, and thus may represent a new checkpoint mechanism whereby Cdc2/Cyclin B1 can be inhibited. With the use of an antisense approach, reduced Gadd45 expression attenuated the suppression of Cdc2/Cyclin B1 activity in UV-irradiated human cells. Taken together, these results implicate Gadd45 in the control of G2/M cell cycle progression after certain stresses.
MeSH terms
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Antibodies, Monoclonal / chemistry
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CDC2 Protein Kinase / antagonists & inhibitors
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CDC2 Protein Kinase / genetics
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CDC2 Protein Kinase / metabolism*
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Carcinoma / genetics
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Carcinoma / radiotherapy
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Cell Cycle Proteins
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Colonic Neoplasms / genetics
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Colonic Neoplasms / radiotherapy
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Cyclin B / antagonists & inhibitors
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Cyclin B / immunology
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Cyclin B / metabolism*
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Cyclin B1
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Cyclin E / metabolism
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Enzyme Inhibitors / pharmacology
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Enzyme-Linked Immunosorbent Assay
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Epitopes
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GADD45 Proteins
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Genes, myc
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Histones / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins
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Nuclear Proteins
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Nucleosome Assembly Protein 1
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Precipitin Tests
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Proteins / genetics
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Proteins / metabolism*
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RNA, Antisense / pharmacology
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Recombinant Proteins / genetics
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Recombinant Proteins / metabolism
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Staurosporine / pharmacology
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Transfection
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Tumor Cells, Cultured
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Tumor Suppressor Protein p53 / genetics
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Tumor Suppressor Protein p53 / metabolism*
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Ultraviolet Rays
Substances
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Antibodies, Monoclonal
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CCNB1 protein, human
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Cell Cycle Proteins
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Cyclin B
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Cyclin B1
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Cyclin E
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Enzyme Inhibitors
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Epitopes
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Histones
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Intracellular Signaling Peptides and Proteins
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NAP1L1 protein, human
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Nuclear Proteins
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Nucleosome Assembly Protein 1
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Proteins
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RNA, Antisense
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Recombinant Proteins
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Tumor Suppressor Protein p53
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CDC2 Protein Kinase
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Staurosporine