IFN regulatory factor-1-mediated transcriptional activation of mouse STAT-induced STAT inhibitor-1 gene promoter by IFN-gamma.
STAT-induced STAT inhibitor-1 (SSI-1), also referred to as suppressor of cytokine signaling-1 and JAK-binding protein, is a member of a new family, the members of which are negative regulators of cytokine signals. SSI-1 is induced by various cytokines; however, the transcriptional mechanism of the SSI-1 gene is not fully understood. Here, we showed that transcription of the mouse SSI-1 gene was initiated from six adjoining sites accompanying three GC boxes and a single GC box-like element near them, but not from the TATA box or an initiator sequence. We also showed that IFN-gamma induced SSI-1 mRNA more strongly than IL-6 in NIH-3T3 fibroblasts and that this IFN-gamma effect was mediated by Stat1. To determine the signal pathway downstream of Stat1, transcriptional activities of several mutant promoters were examined. The region mediating stimulatory effect of IFN-gamma to the gene transcription was localized to the -88/-60 region containing three tandem GAAA units, named variant IFN-gamma-responsive element (VIRE), while four IFN-gamma activation site (GAS)-like elements located far upstream were not related to the IFN-gamma response. Gel-shift assays revealed that IFN-gamma induced IFN regulatory factor-1 (IRF-1) binding to VIRE, but not that of IRF-2 or three components of ISGF3. Furthermore, forced expression of IRF-1 mimicked and that of IRF-2 inhibited the stimulatory effect of IFN-gamma on SSI-1 gene transcription. Finally, mouse embryonal fibroblasts lacking IRF-1 showed impaired SSI-1 mRNA induction by IFN-gamma. These results demonstrated that IRF-1, which is induced by activation of Stat1, mediated transcriptional activation of the SSI-1 gene by IFN-gamma via VIRE.
Saito
H
H
Department of Molecular Medicine, Osaka University Medical School, and Osaka University, Suita City, Osaka, Japan. saitoh@imed3.med.osaka-u-ac.jp
Morita
Y
Y
Fujimoto
M
M
Narazaki
M
M
Naka
T
T
Kishimoto
T
T
D016475:3T3 Cells / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D004357:Drug Synergism; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000378:metabolism; D006133:Growth Substances / Q000494:pharmacology; D050856:Interferon Regulatory Factor-1; D007371:Interferon-gamma / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000276:immunology*; D012333:RNA, Messenger / Q000096:biosynthesis; D012097:Repressor Proteins; D020218:Response Elements / Q000276:immunology; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D020080:Tandem Repeat Sequences / Q000276:immunology; D015534:Trans-Activators / Q000502:physiology*; D014158:Transcription, Genetic / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology
D002352:Carrier Proteins; D016207:Cytokines; D004268:DNA-Binding Proteins; D006133:Growth Substances; D050856:Interferon Regulatory Factor-1; C494258:Irf1 protein, mouse; D010750:Phosphoproteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C491590:Socs1 protein, mouse; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma