Sequence of the pig major histocompatibility region containing the classical class I genes

A segment comprising 307,078 nucleotides of the pig major histocompatibilit y complex (SLA) was completely sequenced. The segment corresponded to the e ntire SLA classical class I-containing region of the serologically defined SLA HO1 haplotype. In all, 11 genes were characterized, comprising 7 class I genes located on the centromeric part of the sequence (SLA-1, 2, 3, 4, 5, 9, and 11) and 4 ring finger-related family genes located on its telomeric part. No member of one family was intermingled with a member of the other or with any third-party gene. All class I genes except SLA-11 were similarl y orientated. The SLA-1, 2, and 3 genes displayed both promoter and overall coding regions compatible with normal functions. The SLA-4, 11, and 9 gene s were considered pseudogenes because they exhibited marked anomalies. Alth ough the SLA-5 gene had a complete coding region, it displayed mutations in promoter elements which could modify its expression. The great molecular s imilarity observed among the class I genes extended far outside them, and r esulted from segmental duplications. The ring finger genes exhibited great homology with their human. counterparts. In pig, one of these genes appeare d to correspond to a complete gene which in humans is probably a pseudogene . In all, the 11 genes. characterized span about 20% of the total sequence. The remaining 80% consists of interspersed repeat elements. The present re sults, together with the sequence previously reported involving the SLA cla ss I-related genes, open the way for a better understanding of pig MHC orga nization.