Differential effects of cdk2 and cdk3 on the control of pRb and E2F function during G1 exit.
The cyclin-dependent kinases cdk2 and cdk3 are required for the G1-S transition in mammalian cells. Here we show that G1 arrest induced by the corresponding dominant-negative mutants of these enzymes, cdk2dn or cdk3dn, is resistant to the action of SV40 T antigen (T). In the presence of cdk2dn, T released active E2F from negative control by pRb and its related family members (pocket proteins) but failed to induce S-phase. Therefore, among other targets, cdk2 also phosphorylates nonpocket protein substrates in promoting S-phase entry, and T does not mimic all cdk2 functions. In the presence of cdk3dn, however, T failed to induce cell cycle progression or stimulate E2F-dependent transcription activity. Dominant-negative cdk3 inhibited E2F-1, E2F-2, and, less significantly, E2F-3, but not E2F-4 transcription activity. The inhibition occurred in a pRb-independent manner and did not affect the DNA-binding capacity of the transcription factor. Cdk3 bound specifically to E2F-1/DP-1 complexes in vivo, most likely through DP-1. Thus, cdk3 function contributes to the activation of E2F-1, E2F-2, and partially E2F-3 and, thereby, participates in the process of S-phase entry.
Hofmann
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Division of Neoplastic Disease Mechanisms, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
Livingston
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DM
D000957:Antigens, Viral, Tumor; D001483:Base Sequence; D042846:CDC2-CDC28 Kinases; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D051357:Cyclin-Dependent Kinase 2; D056849:Cyclin-Dependent Kinase 3; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050699:E2F3 Transcription Factor; D016193:G1 Phase / Q000502:physiology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D007399:Interphase / Q000502:physiology*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D056465:Retinoblastoma-Binding Protein 1; D016196:S Phase / Q000502:physiology; D013539:Simian virus 40; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D000957:Antigens, Viral, Tumor; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D050699:E2F3 Transcription Factor; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C098776:CDK3 protein, human; D051357:Cyclin-Dependent Kinase 2; D056849:Cyclin-Dependent Kinase 3; D018844:Cyclin-Dependent Kinases