Nucleotide Sequences and the Molecular Evolution of the DMA and DMB Genes of the Bovine Major Histocompatibility Complex

Abstract

cDNA clones encoding the bovine major histocompatility complex (MHC) class II DM α- and β-chains were isolated and characterized. The BoLA-DMA cDNA clone, MA7, encoded a primary translated product of 260 amino acids, which included a signal peptide of 26 amino acids and a mature polypeptide of 234 amino acids. The BoLA-DMB cDNA clone, MB6, encoded a primary translated product of 262 amino acids, with a signal peptide of 18 amino acids and a mature polypeptide of 244 amino acids. Comparison of the sequences and construction of a phylogenetic tree revealed that both clones are more closely related to human and mouse DM genes than to genes for conventional bovine class II α- and β-chains. Thus, since the bovine DMA and DMB genes are so different from other class II sequences and show evidence of strong conservation (>70%) among the bovine, mouse and human homologues, it seems likely that each of these cDNA clones encodes a functional product, which might perform an important function, as previously established in studies in mouse and man.