title: The cell cycle-regulated B-Myb transcription factor overcomes cyclin-dependent kinase inhibitory activity of p57(KIP2) by interacting with its cyclin-binding domain.
abstract: The cell cycle-regulated B-Myb transcription factor is required for early embryonic development and is implicated in regulating cell growth and differentiation. In addition to its transcriptional regulatory properties, recent data indicate that B-Myb can release active cyclin/Cdk2 activity from the retinoblastoma-related p107 protein by directly interacting with the p107 N terminus. As this p107 domain has homology to the cyclin-binding domains of the p21(Waf1/Cip1) family of cyclin-dependent kinase inhibitors (CKIs), we investigated in this study whether B-Myb could also interact with these CKIs. No in vivo interaction was found with either p21(Waf1/Cip1) or p27(KIP1), however, binding to p57(KIP2) was readily detectable in both in vivo and in vitro assays. The B-Myb-interacting region of p57(KIP2) mapped to the cyclin-binding domain. Consistent with this, B-Myb competed with cyclin A2 for binding to p57(KIP2), resulting in release of active cyclin/Cdk2 kinase. Moreover, B-Myb partially overcame the ability of p57(KIP2) to induce G1 arrest in Saos-2 cells. Despite similarities with previous p107 studies, the B-Myb domains required for interaction with p57(KIP2) were quite different from those implicated for p107. Thus, it is evident that B-Myb may promote cell proliferation by a non-transcriptional mechanism that involves release of active cyclin/Cdk2 from p57(KIP2) as well as p107.
authors.affiliation: Ludwig Institute for Cancer Research and Department of Virology, Faculty of Medicine, Imperial College London, Norfolk Place, London W2 1PG, United Kingdom.
authors.forename: Manel
authors.initials: M
authors.lastname: Joaquin
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Watson
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D015153:Blotting, Western; D042846:CDC2-CDC28 Kinases / Q000378:metabolism; D018797:Cell Cycle Proteins; D002455:Cell Division; D019925:Cyclin A / Q000378:metabolism; D056751:Cyclin A2; D051357:Cyclin-Dependent Kinase 2; D050761:Cyclin-Dependent Kinase Inhibitor p57; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D016213:Cyclins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism; D016193:G1 Phase; D017353:Gene Deletion; D005982:Glutathione Transferase / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012516:Osteosarcoma; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D050720:Retinoblastoma-Like Protein p107; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
chemical_list: C503721:CCNA2 protein, human; C493964:CDKN1C protein, human; D018797:Cell Cycle Proteins; D019925:Cyclin A; D056751:Cyclin A2; D050761:Cyclin-Dependent Kinase Inhibitor p57; D016213:Cyclins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C064352:MYBL2 protein, human; D009687:Nuclear Proteins; D010446:Peptide Fragments; C493844:RBL1 protein, human; D011993:Recombinant Fusion Proteins; D050720:Retinoblastoma-Like Protein p107; D015534:Trans-Activators; D005982:Glutathione Transferase; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases