title: pRB binds to and modulates the transrepressing activity of the E1A-regulated transcription factor p120E4F.
abstract: The retinoblastoma protein pRB is involved in the transcriptional control of genes essential for cell cycle progression and differentiation. pRB interacts with different transcription factors and thereby modulates their activity by sequestration, corepression, or activation. We report that pRB, but not p107 and p130, binds to and facilitates repression by p120(E4F), a ubiquitously expressed GLI-Kruppel-related protein identified as a cellular target of E1A. The interaction involves two distinct regions of p120(E4F) and the C-terminal part of pRB. In vivo pRB-p120(E4F) complexes can only be detected in growth-arrested cells, and accordingly contain the hypophosphorylated form of pRB. Repression of an E4F-responsive promoter is strongly increased by combined expression of p120(E4F) and pRB, which correlates with pRB-dependent enhancement of p120(E4F) binding activity. Elevated levels of p120(E4F) have been shown to block growth of mouse fibroblasts in G(1). We find this requires pRB, because RB(-/-) fibroblasts are significantly less sensitive to excess p120(E4F).
authors.affiliation: Institut de Génétique Moléculaire, Unité Mixte de Recherche 5535, IFR 24, Centre National de la Recherche Scientifique, 1919 Route de Mende, 34293, Montpellier cedex 5, France.
authors.forename: L
authors.initials: L
authors.lastname: Fajas
authors.forename: C
authors.initials: C
authors.lastname: Paul
authors.forename: O
authors.initials: O
authors.lastname: Zugasti
authors.forename: L
authors.initials: L
authors.lastname: Le Cam
authors.forename: J
authors.initials: J
authors.lastname: Polanowska
authors.forename: E
authors.initials: E
authors.lastname: Fabbrizio
authors.forename: R
authors.initials: R
authors.lastname: Medema
authors.forename: M L
authors.initials: ML
authors.lastname: Vignais
authors.forename: C
authors.initials: C
authors.lastname: Sardet
mesh_terms: D017500:Adenovirus E1A Proteins / Q000378:metabolism*; D017504:Adenovirus E4 Proteins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002455:Cell Division; D006131:Growth Inhibitors; D051379:Mice; D009154:Mutation; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism*; D016335:Zinc Fingers
chemical_list: D017500:Adenovirus E1A Proteins; D017504:Adenovirus E4 Proteins; D006131:Growth Inhibitors; D012097:Repressor Proteins; D016160:Retinoblastoma Protein; C411663:transcription factor p120(E4F)