title: WAF1 retards S-phase progression primarily by inhibition of cyclin-dependent kinases.
abstract: The p21(WAF1/CIP1/sdi1) gene product (WAF1) inhibits DNA replication in vitro (J. Chen, P. Jackson, M. Kirschner, and A. Dutta, Nature 374:386-388, 1995; S. Waga, G. Hannon, D. Beach, and B. Stillman, Nature 369:574-578, 1994), but in vivo studies on the antiproliferative activity of WAF1 have not resolved G1-phase arrest from potential inhibition of S-phase progression. Here, we demonstrate that elevated WAF1 expression can retard replicative DNA synthesis in vivo. The WAF1-mediated inhibitory effect could be antagonized by cyclin A, cyclin E, or the simian virus 40 small-t antigen with no decrease in the levels of WAF1 protein in transfected cells. Proliferating-cell nuclear antigen (PCNA) overexpression was neither necessary nor sufficient to antagonize WAF1 action. Expression of the N-terminal domain of WAF1, responsible for cyclin-dependent kinase (CDK) interaction, had the same effect as full-length WAF1, while the PCNA binding C terminus exhibited modest activity. We conclude that S-phase progression in mammalian cells is dependent on continuing cyclin and CDK activity and that WAF1 affects S phase primarily through cyclin- and CDK-dependent pathways.
authors.affiliation: Laboratory of Molecular Growth Regulation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-2753, USA.
authors.forename: V V
authors.initials: VV
authors.lastname: Ogryzko
authors.forename: P
authors.initials: P
authors.lastname: Wong
authors.forename: B H
authors.initials: BH
authors.lastname: Howard
mesh_terms: D000952:Antigens, Polyomavirus Transforming / Q000235:genetics; D042846:CDC2-CDC28 Kinases; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D050759:Cyclin-Dependent Kinase Inhibitor p21; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology; D016213:Cyclins / Q000235:genetics / Q000502:physiology*; D004261:DNA Replication; D004791:Enzyme Inhibitors; D016193:G1 Phase / Q000502:physiology; D015870:Gene Expression; D006801:Humans; D012516:Osteosarcoma; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins; D016196:S Phase / Q000502:physiology*; D013539:Simian virus 40 / Q000276:immunology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000952:Antigens, Polyomavirus Transforming; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D018809:Proliferating Cell Nuclear Antigen; D011518:Proto-Oncogene Proteins; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D010749:Phosphoprotein Phosphatases