Functional domains of interferon regulatory factor I (IRF-1).
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.
Schaper
F
F
Gesellschaft für Biotechnologische Forschung mbH, Mascheroder Weg 1, 38124 Braunschweig, Federal Republic of Germany.
Kirchhoff
S
S
Posern
G
G
Köster
M
M
Oumard
A
A
Sharf
R
R
Levi
B Z
BZ
Hauser
H
H
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
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