Structure of the human C2 gene.

A human genomic cosmid clone, S22A, was used to characterize the structure of the human C2 gene. Eighteen exons spanning 18 kb of DNA were mapped by nucleotide sequencing of exon-containing subclones and by Southern blotting. Introns vary in length between 83 bp and 4.4 kb and all intron/exon boundaries follow the AG/GT consensus rule for splicing. Exon 1 encodes 270 bp of the 5'-untranslated region of the C2 cDNA C2HL5-3 and 15 amino acids of the leader peptide. The three short consensus repeats of C2b are encoded by the single exons 2, 3, and 4, respectively. The von Willebrand factor type A-like domain of C2a is encoded by exons 6-10 and the serine protease domain by exons 11-18. Exons 5 and 15 appear to be unique to the C2 and factor B genes.