A novel gene, G7e, resembling a viral envelope gene, is located at the recombinational hot spot in the class III region of the mouse MHC.

DNA sequence analysis of a segment of 15 kb, situated between G7b and G7a and present in the mouse but absent in human, revealed about 11 kb of DNA harboring a large number of repetitive sequences and 4 kb harboring a novel gene, G7e. This gene is transcribed in lymphoid tissues, having a 3-kb mRNA. The cDNA sequence of G7e shows stretches of nucleotide homology with murine leukemia virus (MuLV) envelope genes, and the predicted protein encompasses viral envelope motifs. The finding of a gene resembling MuLV envelope genes, flanked by a long terminal repeat and gag- and pol-like sequences, leads to the assumption that G7b and G7a in the mouse were separated through the insertion of a provirus, an event that might have taken place even before speciation of rat and mouse. The 15-kb interval forms a part of a 50-kb region, between Hsp70.3 and G7, where recombination preferentially takes place. Several disease susceptibility genes have been mapped to this same interval. The position of G7e in or in the vicinity of a recombinational hot spot might not be coincidental. The presence of adjacent putative recombination regulatory sequences is suggestive for the location of the crossover sites of recombination in this interval.