CLONING OF A HUMAN PLATELET-ACTIVATING-FACTOR RECEPTOR GENE - EVIDENCE FOR AN INTRON IN THE 5'-UNTRANSLATED REGION

A clone encoding a gene for a human platelet-activating factor (PAF) receptor has been isolated from a human genomic library. A 6-kb Hind Ill fragment was subcloned and was found to contain a full coding sequence identical with that previously reported for cDNA clones encoding PAF receptors from leukocyte cDNA libraries. Sequencing of the 6-kb Hind III fragment upstream from the start codon revealed that the 5'-untranslated region deviated from reported cDNA sequences beginning at base -39, suggesting the presence of an intron in this region. Consensus sequences for a splice junction appear appropriately located at the predicted 3' end of the purported intron. Restriction map analysis of the region revealed that the size of the intron in the 5'-untranslated region was at least 16 kb. These data indicate that a gene for a human PAF receptor is present in the genome without introns in the coding sequence and that splicing of mRNA encoding PAF receptors appears to occur in the 5'-untranslated region.