title: Heregulin regulates the ability of the ErbB3-binding protein Ebp1 to bind E2F promoter elements and repress E2F-mediated transcription.
abstract: The ErbB3/4 ligand heregulin (HRG) profoundly affects cell growth and differentiation, but its mechanism of action is poorly understood. Ebp1, a protein isolated by its binding to ErbB3, inhibits cell growth and represses transcription of E2F-regulated cell cycle genes. Since Ebp1 shares 38% identity with a Schizosaccharomyces pombe DNA-binding protein, we postulated that Ebp1 could bind E2F consensus elements in an HRG-inducible manner, leading to transcriptional repression. We show here that GST-Ebp1 bound to the DNA sequence bound by the S. pombe protein. Whereas GST-Ebp1 alone failed to bind E2F1 promoter elements, Ebp1 contained in nuclear lysates associated with E2F1 consensus sequences in the E2F1 promoter. Endogenous Ebp1 was recruited to the E2F1 promoter in vivo as demonstrated by chromatin immunoprecipitation assays. Ebp1 bound E2F consensus oligonucleotides in association with E2F1, retinoblastoma protein, and HDAC2. HRG regulated the association of Ebp1 with E2F promoter sequences and enhanced the ability of Ebp1 to repress transcription. Our findings suggest that Ebp1, by linking HRG activation of membrane receptors to E2F gene activity, may be a downstream modulator of the effects of HRG on cell cycle progression.
authors.affiliation: Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
authors.forename: Yuexing
authors.initials: Y
authors.lastname: Zhang
authors.forename: Anne W
authors.initials: AW
authors.lastname: Hamburger
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000378:metabolism*; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002454:Cell Differentiation; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism*; D018450:Disease Progression; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D008156:Luciferases / Q000378:metabolism; D020890:Neuregulin-1 / Q000502:physiology*; D009841:Oligonucleotides / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016601:RNA-Binding Proteins; D020893:Receptor, ErbB-3 / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry; D020218:Response Elements; D012568:Schizosaccharomyces / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D008024:Ligands; D020890:Neuregulin-1; D009841:Oligonucleotides; C101633:PA2G4 protein, human; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D004247:DNA; D008156:Luciferases; D005982:Glutathione Transferase; D020893:Receptor, ErbB-3