Functional characterization of IL-13 receptor alpha2 gene promoter: a critical role of the transcription factor STAT6 for regulated expression.
Interleukin (IL)-4 and IL-13 are two structurally and functionally related cytokines that have overlapping but also distinct biological activities. One of the components of the IL-13 receptor, the alpha2 chain (IL-13Ralpha2), has been reported to downregulate the cell responsiveness to IL-13, without affecting IL-4 signaling. Here, we report that TNFalpha synergizes with either IL-4 or IL-13 in inducing the IL-13Ralpha2 chain at both the mRNA and protein levels in the HaCaT human keratinocyte cell line. Further studies by 5'RACE identified as yet undescribed exonic sequences of the IL-13Ralpha2 5'UTR, provided evidence for the expression of alternatively spliced IL-13Ralpha2 transcripts and defined the transcription start of the IL-13Ralpha2 gene. A 1.5 kb region upstream of the first exon of the IL-13Ralpha2 gene displayed basal promoter activity when inserted in a reporter plasmid and transiently transfected in HaCaT cells. This promoter activity was further increased in response to IL-4 and IL-13. Furthermore, by electrophoretic mobility shift assay and site-directed mutagenesis, we showed that the IL-4/IL-13-induced promoter activity depended upon a positively acting STAT6 response element. Finally, TNFalpha was shown to potentiate IL-4/IL-13-induced IL-13Ralpha2 promoter activity when the same reporter construct was studied in stably but not in transiently transfected cells. These results suggest that the synergistic effect of TNFalpha on IL-4/IL-13-induced IL-13Ralpha2 expression is dependent upon chromatin re-modeling events.
David
Muriel D
MD
INSERM U461, Faculte de Pharmacie, 5, rue JB Clement, 92296 Chatenay Malabry Cedex, France.
Bertoglio
Jacques
J
Pierre
Josiane
J
D024506:5' Flanking Region; D001483:Base Sequence; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D066298:In Vitro Techniques; D018793:Interleukin-13 / Q000378:metabolism; D053661:Interleukin-13 Receptor alpha1 Subunit; D015847:Interleukin-4 / Q000378:metabolism; D015603:Keratinocytes; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D018123:Receptors, Interleukin / Q000235:genetics* / Q000378:metabolism; D053660:Receptors, Interleukin-13; D050800:STAT6 Transcription Factor; D017422:Sequence Analysis, DNA; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism
C508181:IL13RA1 protein, human; D018793:Interleukin-13; D053661:Interleukin-13 Receptor alpha1 Subunit; D018123:Receptors, Interleukin; D053660:Receptors, Interleukin-13; D050800:STAT6 Transcription Factor; C494101:STAT6 protein, human; D015534:Trans-Activators; D015847:Interleukin-4