GENOMIC ORGANIZATION OF THE HUMAN C3A RECEPTOR

The human C3a receptor (C3aR) mediates the activation of cells by the potent proinflammatory chemoattractant C3a, an anaphylatoxin, generate d in the early phase of an inflammatory reaction by proteolytic cleava ge of the complement component C3. To understand the molecular mechani sms that regulate C3aR gene expression, we initiated studies to determ ine its genomic and mRNA organization. We now report the following nov el findings: (1) The C3aR is a single-copy gene as shown by Southern h ybridization of human genomic DNA. (2) Using PCR amplification of DNA from monochromosomal somatic cell hybrid and radiation hybrid panels, the C3aR locus was mapped to chromosome 12p13. (3) Genomic DNA clones encompassing the C3aR locus were isolated from a human genomic DNA lib rary and characterized by restriction mapping, Southern blotting, PCR analysis and DNA sequencing. Comparison of the genomic with the known cDNA sequences revealed a single similar to 6-kb intron sequence locat ed 11 bp upstream of the ATG initiation codon. The open reading frame and the complete 3' untranslated region are encoded on a single exon.