Nucleotide sequences and the molecular evolution of the DMA and DMB genes of the bovine major histocompatibility complex

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.