Interplay between repressing and activating domains defines the transcriptional activity of IRF-1.
Interferon regulatory factor-1 (IRF-1) is a transcriptional activator with weak activation capacity. By defining the transcriptional activation domain of IRF-1 we identified two activator fragments located between amino acids 185 and 256 functioning in an additive manner. Another fragment of IRF-1, which has no activator function alone, acts as a strong enhancer element of these activator sequences. This enhancer element resides between the activator domains and the C-terminus. In addition, we identified a novel type of inhibitory domain in the N-terminal 60 amino acids of IRF-1 which strongly inhibits its transcriptional activity. Because this fragment is conserved in all interferon regulatory factors, we found similar repression effects in the corresponding fragments in IRF-2, IRF-3 and interferon consensus sequence binding protein (ICSBP/IRF-8). Interestingly, the corresponding sequence in p48/IRF-9 is divergent, so that it does not show this inhibitory activity. A five-amino-acid sequence distinguishes the p48/IRF-9 N-terminus from the homologous parts in other interferon regulatory factors containing the repressing function. Replacing the diverged amino acids in IRF-1 with the corresponding sequence of p48/IRF-9 resulted in a loss of inhibitory activity within IRF-1. The opposing activities within interferon regulatory factors may contribute to balanced or tuned regulation of gene activation, depending on the promoter context.
Kirchhoff
S
S
National Research Center for Biotechnology, Braunschweig, Germany.
Oumard
A
A
Nourbakhsh
M
M
Levi
B Z
BZ
Hauser
H
H
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D004797:Enzyme-Linked Immunosorbent Assay; D005656:Fungal Proteins / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D050856:Interferon Regulatory Factor-1; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D000596:Amino Acids; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D050856:Interferon Regulatory Factor-1; C494258:Irf1 protein, mouse; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D008156:Luciferases; D015500:Chloramphenicol O-Acetyltransferase