title: Allelic diversity at class II DRB1 and DQB loci of the pig MHC (SLA).
abstract: The loci encoding the beta chain of the pig major histocompatibility complex (MHC) class II antigens, SLA-DR and -DQ, have been known to exhibit a remarkable degree of allelic polymorphism. Here, to understand the generation of SLA class II polymorphism, 25 SLA-DRB1 and 24 SLA-DQB genes including newly identified 12 SLA-DRB1 and 7 SLA-DQB genes obtained from miniature pigs were analyzed based on the nucleotide and deduced amino acid sequences. Most of the allelic diversity was attributed to the variable sequences which encode a beta1 domain consisting of a beta-pleated sheet followed by an a helix. In the beta1 domain coding region, there were four GC-rich sequences, which have been considered to involve the intra-exon sequence exchange also in other gene evolutions. The first and second GC-rich sequences were alpha-like sequences, which have been shown to be a putative recombination signal, and were stably conserved among SLA-DRB1 and DQB genes. These alpha-like sequences identified in SLA-DRB1 and SLA-DQB were found to encode the first turning point of the beta-pleated sheet and the boundary between the beta-pleated sheet and the alpha helix. Analysis of clustered sequence variation also suggested intra-exon gene conversions in which the alpha-like sequences act as putative breakpoints. In addition to point mutations and selection mechanism, intra-exon gene conversions must be an important mechanism in the generation of allelic polymorphism at the SLA-DRB1 and SLA-DQB.
authors.affiliation: Department of Molecular Immunology, School of Agriculture and Life Sciences, University of Tokyo, Japan.
authors.forename: T H
authors.initials: TH
authors.lastname: Kanai
authors.forename: Y
authors.initials: Y
authors.lastname: Tanioka
authors.forename: M
authors.initials: M
authors.lastname: Tanigawa
authors.forename: Y
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: S
authors.initials: S
authors.lastname: Ueda
authors.forename: T
authors.initials: T
authors.lastname: Onodera
authors.forename: Y
authors.initials: Y
authors.lastname: Matsumoto
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D005802:Genes, MHC Class II; D014644:Genetic Variation; D006683:HLA-DQ Antigens / Q000235:genetics*; D059866:HLA-DQ beta-Chains; D006684:HLA-DR Antigens / Q000235:genetics*; D059811:HLA-DRB1 Chains; D008969:Molecular Sequence Data; D010802:Phylogeny; D011110:Polymorphism, Genetic; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid; D013552:Swine
chemical_list: D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C057615:HLA-DQbeta antigen; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains