Identification and Characterization of the C is-Act ing Transcriptional Elements in the Regulated Expression of the 11-8 Receptor Type B Gene

IL-8RA and IL-8RB belong to the rhodopsin superfamily of G-protein coupled receptors. Both receptors are abundantly expressed on neutrophils and to a lesser extent on myelomonocytic cells lines and T cells. Preliminary studies in our laboratory indicate the presence of constitutive transcriptional regulatory elements and a G-CSF inducible region within the IL-8RB gene promoter from nucleotide position -118 to +32. To better define these regulatory elements, 5' deletion constructs were created in a luciferase reporter gene vector. Transient transfection of these constructs into the T cell line Jurkat and the myelomonocytic cell line U937 have identified a transcriptionally active promoter region found upstream from the IL-8RB TATA-box equivalent and denned by nucleotide positions -118 to -31. This putative enhancer region was shown to activate transcription initiation from a classical TATAbox in forward and reverse orientation when cloned upstream of the reporter gene. Furthermore, an overlapping region from -133 to -70 possessed similar activity. Both regions are GC-rich and contain consensus binding sites for the transcription factor SP-1. The region from -70 to -31 additionally contains a putative AP-2 site. Gel mobility shift assays are being used to identify transcription factor binding sites within these promoter regions. These studies will ultimately lead to the identification of the trans-acting factors involved in the constitutive, tissue-specific, and growth factor-inducible expression of the IL-8RB gene.