Molecular Characterization of the Recombination Region of Six Murine Major Histocompatibility Complex (MHC) I-region Recombinants

Using Southern DNA hybridization techniques, restriction enzyme site polymorphisms have been used to correlate the molecular maps of the murine major histocompatibility complex (MHC) I region with the genetic map derived from analyses of recombinant mouse strains. The data indicated that the DNA that maps between the I-A and I-E subregions is limited to 3.4 kilobases (kb) and includes the 3' end of the E beta gene. According to classical genetic mapping by recombinational analysis of serological markers, this region should encode the I-B and I-J subregions. These observations are surprising in two respects. First, 3.4 kb is a small amount of DNA to encode even one complete murine gene. Second, this region, which putatively encodes the I-J gene, appears to reside at least partially within the E beta gene. To analyze these apparent paradoxes, further, we cloned the 3.4-kb region in question from six I-region combinant strains [B10.A(3R), B10.a(5R), B10.A(4R), B10.GD, B10.HTT, and B10.S(9R)] and four strains used in the derivation of the recombinants (B10.D2, B10.A, C57BL/10, and ASW) into a lambda phage vector. By direct restriction enzyme mapping of polymorphic sites, we have confirmed the previously identified boundaries of the I-A and I-E subregions and have narrowed the estimate of the distance between these subregions to approximately 2.0 kb of DNA. This 2.0-kb region encompasses part of the intron between the first- (beta 1) and second-domain (beta 2) exons and the second-domain exon (beta 2) of the E beta gene.(ABSTRACT TRUNCATED AT 250 WORDS)