CLONING, LOCALIZATION, AND STRUCTURE OF NEW MEMBERS OF THE BUTYROPHILIN GENE FAMILY IN THE JUXTA-TELOMERIC REGION OF THE MAJOR HISTOCOMPATIBILITY COMPLEX

New members of the butyrophilin (BT) gene family have been identified by cDNA and genomic cloning. Six genes are described: BT2.1, 2.2, 2.3, and BT3. 1, 3.2, and 3.3. BT2, BT3, and BT form three distinct subfam ilies sharing about 95% amino acid identity at the intra subfamily lev el and 50% identity at the interfamily level. All the BT2 and BT3 subf amily members map close to BT in the juxta-telomeric region of the maj or histocompatibility complex. The BT2 members have the canonical stru ctural organization of BT, i.e., two immunoglobulin domains followed b y a transmembrane anchor and a B30.2 intracytoplasmic domain. In the B T3 subfamily, only BT3.3 has the structural organization of BT. The tw o other genes, BT3.1 and BT3.2, code for putative protein without the B30.2 domain. In the case of BT3.2, this is due to an Alu insertion in the B30.2 coding exon, leading to a new polyadenylation site.