title: Association of Pur alpha and E2F-1 suppresses transcriptional activity of E2F-1.
abstract: Protein-protein interaction can play an important role in the control of several biological events including gene transcription, replication and cell proliferation. E2F-1 is a DNA-binding transcription factor which, upon interaction with its target DNA sequence, induces expression of several S phase specific genes allowing progression of the cell cycle. Evidently, the activity of this protein is modulated by its cellular partner, pRb, which in the hypophosphorylated form, binds to E2F-1 and inactivates its transcriptional ability. In this study, we have demonstrated that expression of a sequence-specific single-stranded DNA binding protein, Pur alpha, in cells decreases the ability of E2F-1 to exert its transcriptional activity upon the responsive promoter derived from DHFR. Results from band shift experiments revealed that while Pur alpha does not recognize the double-stranded DNA fragment containing the E2F-1 binding site, it has the ability to inhibit E2F-1 interaction with its target DNA sequence. Results from GST pull-down assays and the combined immunoprecipitation/Western blot analysis of nuclear extracts revealed a direct association of E2F-1 with Pur alpha in the absence of the DNA molecule containing the E2F-1 binding site. The association of Pur alpha with E2F-1 may increase the stability of E2F-1, as a higher level of E2F-1 was detected in cells coexpressing Pur alpha and E2F-1. The importance of these observations with respect to the role of Pur alpha in the control of cell cycle progression is discussed.
authors.affiliation: Center for NeuroVirology and NeuroOncology, MCP Hahnemann University School of Medicine, Philadelphia, PA 19102, USA.
authors.forename: N
authors.initials: N
authors.lastname: Darbinian
authors.forename: G L
authors.initials: GL
authors.lastname: Gallia
authors.forename: M
authors.initials: M
authors.lastname: Kundu
authors.forename: N
authors.initials: N
authors.lastname: Shcherbik
authors.forename: A
authors.initials: A
authors.lastname: Tretiakova
authors.forename: A
authors.initials: A
authors.lastname: Giordano
authors.forename: K
authors.initials: K
authors.lastname: Khalili
mesh_terms: D001253:Astrocytes; D001665:Binding Sites; D002352:Carrier Proteins; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D002460:Cell Line; D002474:Cell-Free System; D016384:Consensus Sequence; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D017930:Genes, Reporter; D006801:Humans; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016160:Retinoblastoma Protein / Q000502:physiology; D056465:Retinoblastoma-Binding Protein 1; D016196:S Phase; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; C501130:PURA protein, human; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D013762:Tetrahydrofolate Dehydrogenase