title: Constitutive expression of E2F-1 leads to p21-dependent cell cycle arrest in S phase of the cell cycle.
abstract: p21 is a potent inhibitor of cyclin-dependent kinases capable of arresting cell cycle progression. p21 is primarily regulated at the transcriptional level by several transcription factors, including p53. Previously, we reported that certain members of the E2F family of transcription factors may activate p21 transcription via a p53-independent mechanism. To further elucidate the consequences of E2F-1-regulated induction of p21, we developed cell lines with a tamoxifen-dependent form of E2F-1. We confirmed direct interaction of E2F-1 with the proximal region of the p21 promoter. Interestingly, elevated E2F-1 activity was sufficient to arrest a substantial subset of cells in S phase and this effect was correlated to and dependent on the induction of p21 protein. Since E2F proteins control genes required for cell cycle progression and are activated by various oncogenic events, we believe that the p21-dependent arrest described in this report represents an additional mechanism that guards against unrestricted cell proliferation.
authors.affiliation: Department of Medicine, University of Illinois at Chicago, 60612, USA.
authors.forename: Senthil K
authors.initials: SK
authors.lastname: Radhakrishnan
authors.forename: Claudine S
authors.initials: CS
authors.lastname: Feliciano
authors.forename: Feridoon
authors.initials: F
authors.lastname: Najmabadi
authors.forename: Andrea
authors.initials: A
authors.lastname: Haegebarth
authors.forename: Eugene S
authors.initials: ES
authors.lastname: Kandel
authors.forename: Angela L
authors.initials: AL
authors.lastname: Tyner
authors.forename: Andrei L
authors.initials: AL
authors.lastname: Gartel
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D011960:Receptors, Estrogen / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D016196:S Phase / Q000235:genetics / Q000502:physiology*; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C493956:CDKN1A protein, human; C493957:Cdkn1a protein, mouse; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C493754:E2f1 protein, mouse; D011960:Receptors, Estrogen; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors