IL-4 and IL-13 induce SOCS-1 gene expression in A549 cells by three functional STAT6-binding motifs located upstream of the transcription initiation site.
Proteins of the suppressors of cytokine signaling (SOCS) family have important functions as negative regulators of cytokine signaling. We show here that SOCS-1 expression can be induced in the human epithelial lung cell line A549 by IL-4 and IL-13. Analysis of reporter gene constructs under control of the SOCS-1 promoter provides evidence that IL-4- and IL-13-induced up-regulation is dependent on three IFN-gamma-activated sequence motifs of the sequence TTC(N)(4)GAA, which is known for binding STAT6. The three motifs are situated close to each other approximately 600 bp upstream of the transcriptional initiation site. When mutations were inserted into all three IFN-gamma-activated sequence motifs at the same time, IL-4-IL-13-induced luciferase activity was abrogated. With single and double mutants, promoter activity was diminished in comparison with the wild-type promoter. STAT6 is therefore required for IL-4-IL-13-dependent SOCS-1 expression in A549 cells, and the three identified binding motifs cooperate to induce maximal transcription. EMSAs conducted with nuclear extracts of IL-4- and IL-13-stimulated A549 cells showed that STAT6 was able to bind to each of the three binding motifs. Finally, cotransfection of a SOCS-1 expression vector inhibited activation of SOCS-1 promoter luciferase constructs. Thus, SOCS-1 is able to autoregulate its expression via a negative feedback loop.
Hebenstreit
Daniel
D
Institute of Chemistry and Biochemistry, University of Salzburg, Salzburg, Austria.
Luft
Petra
P
Schmiedlechner
Angela
A
Regl
Gerhard
G
Frischauf
Anna-Maria
AM
Aberger
Fritz
F
Duschl
Albert
A
Horejs-Hoeck
Jutta
J
D020121:5' Untranslated Regions / Q000378:metabolism / Q000502:physiology*; D020816:Amino Acid Motifs / Q000235:genetics / Q000276:immunology; D001665:Binding Sites / Q000235:genetics / Q000276:immunology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D045744:Cell Line, Tumor; D025461:Feedback, Physiological / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D018793:Interleukin-13 / Q000037:antagonists & inhibitors / Q000502:physiology*; D015847:Interleukin-4 / Q000037:antagonists & inhibitors / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D012097:Repressor Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics* / Q000502:physiology; D050800:STAT6 Transcription Factor; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D018418:Th2 Cells / Q000276:immunology / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism / Q000502:physiology*; D024363:Transcription Initiation Site; D014162:Transfection; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology
D020121:5' Untranslated Regions; D002352:Carrier Proteins; D018793:Interleukin-13; D047908:Intracellular Signaling Peptides and Proteins; D012097:Repressor Proteins; C108944:SOCS1 protein, human; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D000071222:Suppressor of Cytokine Signaling 1 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D015534:Trans-Activators; D015847:Interleukin-4; D007371:Interferon-gamma