The DY genes of the cattle MHC: expression and comparative analysis of an unusual class II MHC gene pair.

The major histocompatibility complex of cattle (BoLA) contains the class II genes DYA and DIB which are transcribed with a dendritic cell restricted distribution. As part of the process to determine whether these genes have any functional significance, we demonstrate that they form a closely linked pair characteristic of other expressed class II MHC molecules. Accepted nomenclature convention suggests that BoLA-DIB should therefore be renamed BoLA-DYB. Analysis of the first full-length DYA and DYB transcripts revealed open reading frames with potential to translate 253 and 259 amino acid proteins, respectively. Comparative sequence analysis between the DY polypeptides and classical cattle, human and mouse class II MHC alpha and beta polypeptide chains revealed 16 unique amino acid residues at positions predicted to form and line the putative peptide-binding region. Expression of tagged constructs demonstrates for the first time that the DY genes of cattle are capable of translating distinctive class II MHC alpha and beta polypeptide chains.