IFN-alpha induces the human IL-10 gene by recruiting both IFN regulatory factor 1 and Stat3.
The anti-inflammatory cytokine IL-10 can be induced by type I IFNs, but the molecular mechanisms involved have remained elusive. With in silico analysis of the human IL-10 promoter we identified a module consisting of an IFN regulatory factor 1 (IRF-1) site and a Stat3 site. We demonstrate that IFN-alpha will induce the binding of IRF-1 and Stat3 to the respective motifs. Mutational analysis revealed that inactivation of the IRF-1 motif substantially reduces trans-activation from 5- to 2-fold and that inactivation of the Stat3 motif completely ablates trans-activation by IFN-alpha. The dominant role of Stat3 in this module was confirmed with the blockade of trans-activation by a dominant negative Stat3. By contrast, Stat1 contributes a minor proportion to the DNA binding to the Stat site, and overexpression will counteract Stat3-mediated trans-activation. The data show that IFN-alpha induces the IL-10 gene via a module consisting of interdependent IRF-1 and Stat3 motifs. Of note, LPS-induced trans-activation does not target this module, since it is independent of the IRF-1 motif but completely depends on Stat3.
Ziegler-Heitbrock
Löms
L
Institute for Immunology, University of Munich, Munich, Germany. lzh1@le.ac.uk
Lötzerich
Mark
M
Schaefer
Annette
A
Werner
Thomas
T
Frankenberger
Marion
M
Benkhart
Elke
E
D020816:Amino Acid Motifs / Q000235:genetics; D002460:Cell Line; D002999:Clone Cells; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic / Q000276:immunology*; D006801:Humans; D050856:Interferon Regulatory Factor-1; D016898:Interferon-alpha / Q000494:pharmacology*; D016753:Interleukin-10 / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000276:immunology; D012097:Repressor Proteins / Q000502:physiology; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D015533:Transcriptional Activation / Q000276:immunology; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C494257:IRF1 protein, human; D050856:Interferon Regulatory Factor-1; D016898:Interferon-alpha; D010750:Phosphoproteins; D012097:Repressor Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D016753:Interleukin-10