Structural characterization of the human interleukin-13 receptor alpha 1 gene promoter

Human cancer cells have been found to express a large number of IL-13 recep tors, We have previously shown that mRNA encoding one of these receptors, I L-13R alpha 1, is increased in cisplatin-resistant cells and is upregulated in tumor cells cultured with cisplatin, To understand the molecular mechan ism of IL-13R alpha 1 gene expression, we cloned approximately 52 kbp of th e IL-13R alpha 1 gene and sequenced the first exon and about 1 kbp of the u pstream DNA. The first exon is 211 bp and contains 88 bp of coding sequence , while the first intron is about 13 kbp in length. The promoter region, wh ich is GC rich, was found to lack both TATA and CCAAT boxes. Transient expr ession assays revealed that transcription of the IL-13R alpha 1 gene was si gnificantly higher in cisplatin-resistant cells than in parental, cisplatin -sensitive cells, Deletion analysis of the IL-13R alpha 1 promoter identifi ed a 70-bp core promoter region upstream of the transcription initiation si te. Electrophoretic gel mobility shift assays showed that a synthetic IL-13 R alpha 1 oligonucleotide (nt -40 to nt -15) bound a nuclear factor from ci splatin-resistant cells to a significantly greater degree than the equivale nt factor from parental cells. This oligonucleotide was found to contain a palindromic sequence with a BstEII recognition site at its center. This pal indromic sequence functions to mediate upregulation of IL-13R alpha 1 promo ter in cisplatin-resistant cells and deletion or disruption of this sequenc e also resulted in severe reduction of the promoter activity. These finding s suggest that IL-13R alpha 1 expression is upregulated at the transcriptio nal level in cisplatin-resistant cells. The characterization of both the IL -13R alpha 1 promoter and the transcription factors binding to it may contr ibute to our understanding of IL-13R alpha 1 regulation in cancer cells. (C ) 1999 Academic Press.