THE MURINE INTERLEUKIN-5 RECEPTOR ALPHA-SUBUNIT GENE - CHARACTERIZATION OF THE GENE STRUCTURE AND CHROMOSOME MAPPING

To understand better the regulation of interleukin-5 receptor alpha-su bunit (IL-5R alpha) expression, we have isolated the genomic clones of mouse IL-5R alpha (mIL-5R alpha) and analyzed the structure of the ge ne. The gene spans more than 35 kb and is composed of 11 exons. We fou nd that two mRNAs encoding secreted forms of mIL-5R alpha result from differential splicing events. We identified the transcriptional start site by primer extension analysis of mIL-5R alpha mRNA. Nucleotide seq uence of the 5'-flanking region contains potential binding sites for t ranscription factor Ap1, AP-1, GATA-1, and PU.1. About 260 bp sequence of the 5'-flanking region exhibited promoter activity when it was lin ked to a promoterless bacterial chloramphenicol acetyltransferase (CAT ) gene. The promoter activity was seen not only in the IL-5-dependent pre-B-cell line Y16, but also in fibroblast cell line NIH-3T3. Compari son of the exon-intron boundaries of mIL-5R alpha genes with those of other members of the cytokine receptor family reveals a conserved evol utionary structure. By fluorescence in situ hybridization analysis, th e mIL-5R alpha gene has been assigned to chromsome 6.