title: Functional domains of interferon regulatory factor I (IRF-1).
abstract: Interferon (IFN) regulatory factors (IRFs) are a family of transcription factors among which are IRF-1, IRF-2, and IFN consensus sequence binding protein (ICSBP). These factors share sequence homology in the N-terminal DNA-binding domain. IRF-1 and IRF-2 are further related and have additional homologous sequences within their C-termini. Whereas IRF-2 and ICSBP are identified as transcriptional repressors, IRF-1 is an activator. In the present work, the identification of functional domains in murine IRF-1 with regard to DNA-binding, nuclear translocation, heterodimerization with ICSBP and transcriptional activation are demonstrated. The minimal DNA-binding domain requires the N-terminal 124 amino acids plus an arbitrary C-terminal extension. By using mutants of IRF-1 fusion proteins with green fluorescent protein and monitoring their distribution in living cells, a nuclear location signal (NLS) was identified and found to be sufficient for nuclear translocation. Heterodimerization was confirmed by a two-hybrid system adapted to mammalian cells. The heterodimerization domain in IRF-1 was defined by studies in vitro and was shown to be homologous with a sequence in IRF-2, suggesting that IRF-2 also heterodimerizes with ICSBP through this sequence. An acidic domain in IRF-1 was found to be required and to be sufficient for transactivation. Epitope mapping of IRF-1 showed that regions within the NLS, the heterodimerization domain and the transcriptional activation domain are exposed for possible contacts with interacting proteins.
authors.affiliation: Gesellschaft für Biotechnologische Forschung mbH, Mascheroder Weg 1, 38124 Braunschweig, Federal Republic of Germany.
authors.forename: F
authors.initials: F
authors.lastname: Schaper
authors.forename: S
authors.initials: S
authors.lastname: Kirchhoff
authors.forename: G
authors.initials: G
authors.lastname: Posern
authors.forename: M
authors.initials: M
authors.lastname: Köster
authors.forename: A
authors.initials: A
authors.lastname: Oumard
authors.forename: R
authors.initials: R
authors.lastname: Sharf
authors.forename: B Z
authors.initials: BZ
authors.lastname: Levi
authors.forename: H
authors.initials: H
authors.lastname: Hauser
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D016384:Consensus Sequence; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D018604:Epitope Mapping; D018014:Gene Transfer Techniques; D050856:Interferon Regulatory Factor-1; D050835:Interferon Regulatory Factors; D007371:Interferon-gamma / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D012097:Repressor Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D000099185:Interferon Regulatory Factor-8
chemical_list: D004247:DNA; D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D050835:Interferon Regulatory Factors; D007371:Interferon-gamma; D019913:Nuclear Localization Signals; D010750:Phosphoproteins; D012097:Repressor Proteins; D014157:Transcription Factors; D000099185:Interferon Regulatory Factor-8; C494258:Irf1 protein, mouse