title: The E2F-1 transcription factor is negatively regulated by its interaction with the MDMX protein.
abstract: Several proteins with important roles in oncogenesis have been shown to regulate the function of the E2F-1 transcription factor, which is known to activate the expression of genes required for proliferation and apoptosis. Here we identify the MDMX oncoprotein as an E2F-1-binding factor, from a yeast-two hybrid screen using a portion of the E2F-1 protein as "bait." We demonstrate that the region within MDMX needed for the E2F-1:MDMX interaction is located in the central part of the protein, C-terminal of the p53-binding domain. The region within E2F-1 needed for this association is adjacent to the DNA binding domain. Further, when expressed in vivo or in vitro the MDMX protein migrates as two isoforms on SDS-PAGE, the faster migrating isoform having the stronger affinity for the E2F-1 proteins. It appears that this interaction reduces the ability of E2F-1 to bind DNA. Expression of MDMX along with E2F-1 and Dp-1 in Saos2 cells reduces the ability of E2F-1 to bind to its consensus DNA sequence, without altering E2F-1 protein levels. These data indicate that the MDMX protein is capable of associating with E2F-1 and negatively regulating its DNA binding ability.
authors.affiliation: Department of Pathology, University of Pennsylvania School of Dental Medicine, 4010 Locust St, Rm 312 Levy Research, Philadelphia 19104-6002, USA.
authors.forename: Gordon D
authors.initials: GD
authors.lastname: Strachan
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Jordan-Sciutto
authors.forename: Ravikumar
authors.initials: R
authors.lastname: Rallapalli
authors.forename: Rocky S
authors.initials: RS
authors.lastname: Tuan
authors.forename: David J
authors.initials: DJ
authors.lastname: Hall
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D005786:Gene Expression Regulation; D006801:Humans; D009687:Nuclear Proteins; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D014157:Transcription Factors