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) r eceptor has been isolated from a human genomic library. A 6-kb Hind Il l fragment was subcloned and was found to contain a full coding sequen ce identical with that previously reported for cDNA clones encoding PA F receptors from leukocyte cDNA libraries. Sequencing of the 6-kb Hind III fragment upstream from the start codon revealed that the 5'-untra nslated region deviated from reported cDNA sequences beginning at base -39, suggesting the presence of an intron in this region. Consensus s equences for a splice junction appear appropriately located at the pre dicted 3' end of the purported intron. Restriction map analysis of the region revealed that the size of the intron in the 5'-untranslated re gion was at least 16 kb. These data indicate that a gene for a human P AF receptor is present in the genome without introns in the coding seq uence and that splicing of mRNA encoding PAF receptors appears to occu r in the 5'-untranslated region.