EXPRESSION SCREENING OF A YEAST ARTIFICIAL CHROMOSOME CONTIG REFINES THE LOCATION OF THE MOUSE H3A MINOR HISTOCOMPATIBILITY ANTIGEN GENE

The H3 complex, on mouse Chromosome 2, is an important model locus for understanding mechanisms underlying non-self Ag recognition during ti ssue transplantation rejection between MHC-matched mouse strains. H3a is a minor histocompatibility Ag gene, located within H3, that encodes a polymorphic peptide alloantigen recognized by cytolytic T cells. Ot her genes within the complex include beta(2)-microglobulin and H3b, A yeast artificial chromosome(YAC) contig is described that spans the in terval between D2Mit444 and D2Mit17, a region known to contain H3a, Th is contig refines the position of many genes and anonymous loci. In ad dition, 23 new sequence-tagged sites are described that further increa se the genetic resolution surrounding H3a, A novel assay was developed to determine the location of H3a within the contig, Representative YA Cs were modified by retrofitting with a mammalian selectable marker, a nd then introduced by spheroplast fusion into mouse L cells. YAC-conta ining L cells were screened for the expression of the YAC-encoded H3a( a) Ag by using them as targets in a cell-mediated lympholysis assay wi th H3a(a)-specific CTLs, A single YAC carrying H3a was identified. Bas ed on the location of this YAC within the contig, many candidate genes can be eliminated. The data position H3a between Tyro3 and Epb4.2, in close proximity to Capn3, These studies illustrate how genetic and ge nomic information can be exploited toward identifying genes encoding n ot only histocompatibility Ags, but also any autoantigen recognized by T cells.