title: Regulation of the retinoblastoma protein-related p107 by G1 cyclin complexes.
abstract: The orderly progression through the cell cycle is mediated by the sequential activation of several cyclin/cyclin-dependent kinase (cdk) complexes. These kinases phosphorylate a number of cellular substrates, among which is the product of the retinoblastoma gene, pRb. Phosphorylation of pRb in late G1 causes the release of the transcription factor E2F from pRb, resulting in the transcriptional activation of E2F-responsive genes. We show here that phosphorylation of the pRb-related p107 is also cell cycle regulated. p107 is first phosphorylated at 8 hr following serum stimulation of quiescent fibroblasts, which coincides with an increase in cyclin D1 protein levels. Consistent with this, we show that a cyclin D1/cdk4 complex, but not a cyclin E/cdk2 complex, can phosphorylate p107 in vivo. Furthermore, phosphorylation of p107 can be abolished by the overexpression of a dominant-negative form of cdk4. Phosphorylation of p107 results in the loss of the ability to associate with E2F-4, a transcription factor with growth-promoting and oncogenic activity. A p107-induced cell cycle block can be released by cyclin D1/cdk4 but not by cyclin E/cdk2. These data indicate that the activity of p107 is regulated by phosphorylation through D-type cyclins.
authors.affiliation: Division of Molecular Carcinogenesis, Netherlands Cancer Institute, Amsterdam.
authors.forename: R L
authors.initials: RL
authors.lastname: Beijersbergen
authors.forename: L
authors.initials: L
authors.lastname: Carlée
authors.forename: R M
authors.initials: RM
authors.lastname: Kerkhoven
authors.forename: R
authors.initials: R
authors.lastname: Bernards
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002352:Carrier Proteins; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D019938:Cyclin D1; D016213:Cyclins / Q000378:metabolism*; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050704:E2F4 Transcription Factor; D005347:Fibroblasts / Q000378:metabolism; D016193:G1 Phase; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D015513:Oncogene Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D056465:Retinoblastoma-Binding Protein 1; D050720:Retinoblastoma-Like Protein p107; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C533431:Arid4a protein, mouse; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050704:E2F4 Transcription Factor; C493763:E2f4 protein, mouse; D009687:Nuclear Proteins; D015513:Oncogene Proteins; C489485:Rbl1 protein, mouse; D056465:Retinoblastoma-Binding Protein 1; D050720:Retinoblastoma-Like Protein p107; D050680:Transcription Factor DP1; D014157:Transcription Factors; D019938:Cyclin D1; D011494:Protein Kinases