Cluster of TRIM genes in the human MHC class I region sharing the B30.2 domain

: The major histocompatibility complex (MHC), a region of high gene density, contains a large number of genes relevant to the immune response, belonging to different multigenic families. We studied the genomic organization and polymorphism of a set of genes in the MHC class I region containing the tripartite motif (TRIM), consisting of a RING domain, B‐box and coiled coil region, and a B30.2‐like domain. A cluster of seven genes at 6p21.33 and two related family members telomeric of the cluster were characterized. All MHC‐encoded TRIM‐B30.2 genes showed moderate levels of polymorphism, affecting predominantly the RING and B‐box domains. In terms of structure, the genes varied by the loss of partial and, in some cases, complete domains. They were strongly conserved in exons 2, 3 and 4, which form the coiled‐coil region. The last exon, encoding the B30.2‐like domain, is shared with the otherwise unrelated butyrophilin‐like (BTN) genes, located 4.3 Mb telomeric of the TRIM‐B30.2 cluster. The data are consistent with multiple, ancient duplications giving rise to a set of related genes.