CLONING, EXPRESSION, SEQUENCE DETERMINATION, AND CHROMOSOME LOCALIZATION OF THE MOUSE COMPLEMENT C3A ANAPHYLATOXIN RECEPTOR GENE

The complement C3a anaphylatoxin receptor (C3aR) is a seven-transmembr ane G-protein coupled chemoattractant receptor that on binding the C3a peptide ligand mediates numerous cellular responses, including histam ine release from mast cells, smooth muscle contraction, and the direct ed migration of eosinophils. To delineate the murine C3aR coding seque nce, gene structure, 5'-flanking region, and chromosome location, cDNA and genomic clones encoding the mouse C3a receptor were isolated, cha racterized, and used in fluorescence in situ hybridization experiments . The results from this study indicate that the murine C3a receptor st ructural gene is a single copy gene of approximately 8 kb comprised of 2 exons which are separated by a large intervening intron of 4724 bp. The first exon encodes 97 bp of 5'-untranslated sequence. Exon 2 enco des the remaining 8 bp of 5'-untranslated sequence and the entire codi ng and 3'-untranslated sequences. This genomic organization is typical of most other chemoattractant receptor genes in that the entire codin g sequence is contained on a single exon. The human and mouse C3a rece ptor genes were localized to syntenic chromosomal bands 12q13.2-3 and 6F1, respectively. No other seven-transmembrane receptor genes, to dat e, have been localized to these chromosomal regions. Primer extension experiments using mouse macrophage RNA indicated a single transcriptio nal initiation site. Sequence analysis 5' of the transcriptional site indicated a TATA-less promoter with possible cis-acting motifs that ma y regulate C3a receptor gene expression. These included the recognitio n sequence for the nuclear transcription factor SP1 and the phorbol es ter response sequence which binds the Fos/Jun heteromeric transcriptio n factor API. (C) 1998 Elsevier Science Ltd. All rights reserved.