STRUCTURE, GENOMIC ORGANIZATION, AND EXPRESSION OF THE HUMAN INTERLEUKIN-8 RECEPTOR-B GENE

Two distinct receptors for the chemoattractant interleukin-8 (designat ed IL-8RA and -B) have been cloned recently. The receptors are express ed almost exclusively on neutrophils and myelomonocytic cell lines. In an attempt to understand the tissue-specific expression and to identi fy transcriptional regulatory elements we have cloned, sequenced, and characterized the human IL-8RB gene. The gene consists of 3 exons, int errupted by two introns of 3 and 5.4 kilobases (kb). A 1065-base pair open reading frame is encoded entirely in the third exon. A 1.4-kb 3'- untranslated region contains clustered AU-rich elements, similar to th ose described for genes regulated by altering mRNA stability. The star t site of transcription was mapped by a modified rapid amplification o f cDNA ends technique and revealed an unexpectedly long 5'-untranslate d region of 423 base pairs. A TATA box equivalent was found in the 5'- flanking region 20 nucleotides upstream of the start of the first exon . The promoter was separated from the ATG-initiation codon by 8.75 kb. Comparison of the IL-8RB promoter with the promoter region of the rec eptor for another chemoattractant ligand, the bacterial peptide f-Met- Leu-Phe, revealed 3 novel but conserved motifs occupying similar posit ions. The immediate 5'-flanking region was GC-rich with 3 SP-1-like an d 2 AP-2 sites identified in close proximity to the transcription star t site. This essential promoter region was found to be responsible for constitutive expression, inducible by granulocyte colony-stimulating factor and controlled by silencer elements located further upstream be tween positions -779 and -118.