Sequence of the gene for murine complement component C4.

The gene for murine complement component C4 lies in the S region of the murine major histocompatibility (H-2) complex; in this paper, we report the nucleotide sequence of this gene. The present sequence extends from a SmaI restriction enzyme cleavage site near the 5' end of the gene to a KpnI restriction enzyme cleavage site 569 nucleotides 3' of the polyadenylation site. The sequence spans 15,956 base pairs and together with previously reported data provides a complete sequence extending from the site of transcriptional initiation to the polyadenylation site. The sequence reveals that the C4 gene has 40 introns which range from 75 to 1089 base pairs in length and which include three murine B1 middle repetitive elements, a MT repeat element, and an apparently novel repeat sequence that is also found in noncoding regions of the murine beta-glucuronidase, lymphotoxin (TNF-beta), and rat alpha-crystallin genes. An intron splits the protein coding sequence precisely at the site of proteolytic activation of C4 by complement protease C1s; however, except for this one case, the intron positions show no striking relationship to the structural features of the C4 protein. The length of the murine C4 gene relative to the isotypic C4A and C4B genes in man suggests the independent loss of a 6-kilobase intron from both murine and human C4 genes.