HIGH POLYMORPHISM OF MHC-E LOCUS IN NONHUMAN-PRIMATES - ALLELES WITH IDENTICAL EXON-2 AND EXON-3 ARE FOUND IN 2 DIFFERENT SPECIES

Thirteen Mhc-E new sequences were found in eight individuals belonging to the Cercopithecinae family, i.e.: Macaca mulatta, Macaca fascicula ris and Cercopithecus aethiops when studying E locus polymorphism. No changes were found in the invariant residues which are required for th e correct conformation of the peptide presenting region which are cons erved in classical Mhc class I molecules from fish and reptiles to hum ans; however, polymorphism of Mhc-E alleles is not limited to the thre e typical hypervariable regions per domain as it is in classical class I alleles. The rate of synonymous and non-synonymous substitutions in the DNA sequence corresponding to the antigen binding site, compared to the remainder of exons 2 and 3 shows that the peptide-binding site is under high evolutionary pressure for stability since only synonymou s substitutions have been found to be accepted in apes. Also, a clear example of trans-species evolution of allelism is found: two identical exon 2 and exon 3 sequences there exist belonging to individuals from different species (Mamu-Mhc-E0101 and Mafa-Mhc-E*04). In addition, t wo Macaca mulatta individuals show an Mhc-E locus duplication. Finally , phylogenetic tree analysis shows that Mhc class I molecules found in Saguinus oedipus (described as Mhc-G homologues) are closer to Mhc-E sequences.