The conserved lymphokine element 0 is a powerful activator and target for corticosteroid inhibition in human interleukin-5 transcription.
The role of eosinophilia in allergic disorders indicates hIL-5 as a potential target for therapy. The conservation of hIL-5 gene proximal elements suggests they are important in controlling expression. Corticosteroids are important in the treatment of allergy, and are powerful inhibitors of IL-5 expression. This study aimed at understanding the role of hIL-5 conserved proximal elements, and elucidating the target of corticosteroid activity, in hIL-5 gene expression. Methods used include transient transfection of PBMC and PER117 cells with hIL-5 deletion constructs, EMSA, Western Blotting, and RT-PCR. The conserved proximal CLE0/TATA elements driving a reporter gene gave similar or higher expression than a 500 bp promoter in primary human T cells and a T-cell line. Two and three copies of IL-5 CLE0 upstream of the silent IL-4 minimal promoter gave 30-45 fold increases in expression in forward orientation, but little activity in reverse orientation. Consequently, CLE0 is a powerful activator but not a classical enhancer. Deletion analysis identified CLE0 as the key element in the inhibition of IL-5 reporter constructs by dexamethasone, and RT-PCR analysis indicated that GILZ expression correlated with dexamethasone-induced inhibition of IL-5. Ectopic expression of GILZ, confirmed by western blotting, gave a 90% inhibition of promoter constructs in absence of dexamethasone. CLE0 is a powerful activator sufficient for the inducible expression of IL-5, and functions when moved upstream in a heterologous promoter. CLE0 is also the main target for IL-5 inhibition by dexamethasone, and we present evidence consistent with a role of GILZ in this.
Arthaningtyas
Estri
E
Curtin University of Technology, Molecular Immunology, Perth, WA, Australia. nonny@bigpond.net.au
Kok
Chee Choy
CC
Mordvinov
Viatcheslav A
VA
Sanderson
Colin J
CJ
D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology*; D004742:Enhancer Elements, Genetic; D006801:Humans; D015848:Interleukin-5 / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D020218:Response Elements; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation
D015848:Interleukin-5; C404226:TSC22D3 protein, human; D014157:Transcription Factors; D003907:Dexamethasone