Characterization of a class Ib gene of the rat major histocompatibility complex

Abstract

The cDNA and a partial genomic sequence of a rat class I major histocompatibility (RT1) gene, 11/3R, is reported here. The sequence contains several unique amino acid residues at certain positions, mutations in exon 7 (which is not expressed), a mutation of the canonical exon 8 stop codon to a sense codon, and includes a long 3' untranslated region (utr). The structure of exon 7 differs from that found in most rat class I genes and resembles exon 7 of most H-2K,D,L,Q genes. Parts of the 3' noncoding region are homologous to the RT1.A-4 and certain H-2 genes. Expression is detectable by northern blot analysis in mitogen-stimulated lymphocytes only, by polymerase chain reaction (PCR) in each tissue tested. After transfection into L cells 11/3R can be shown to be expressible at the cell surface. Probes derived from the 3' noncoding part crosshybridize with a number of restriction fragments which map to the RT1.C region, thus defining a subfamily of RT1.C region genes. Several members of this subfamily are deleted in the lm1 RT1 mutant. The 11/3R gene presents typical features of a class Ib gene. Aspects of evolution and the potential function of the gene are discussed.

Multiple TL-like loci in the grc-G/C region of the rat

“…There is molecular evidence for a grc homolog in the mouse (Vincek et al 1990;Hunt et al 1993), and there is clinical evidence for a grc-like region in the human (Ho et al 1994;. The G/C region has many class I loci (Palmer et al 1983;GUnther et al 1985;Cortese Hassett et al 1986Jameson et al 1992;Rothermel et al 1993), some of which encode weakly immunogenic molecules that have a very restricted polymorphism. Genetic mapping studies (Kohoutova et al 1980;Stock and Gtinther 1982;Inomata et al 1986;Kunz et al 1989) place these loci 1.4-3 cM from RT1.A.…”

Rat RT1 orthologs of mouse H2-M class lb genes

“…Only in exon 4 does RT1.M3 show slightly greater similarity to the rat class I genes (92%-94%), perhaps due to selection through interaction with [32-microglobulin (~2m) or CD8. Exon 5 of RT1.M3, which encodes the transmembrane region, lacks the 18 basepair (bp) insertion relative to mouse that distinguishes many rat class I genes (Rada et al 1990), including RZBM1 (Parker et al 1990) but not ll/3R (Rothermel et al 1993), both class Ib genes from the RTI_ C region.…”

“…Numerous substitutions on top of the a-helices can explain the inability of mouse CTL restricted by H2-M3 to crossreact with RT1.M3 (Fischer Lindahl and Hausmann 1983). In the a3 domain, RT1.M3 has Leu191, characteristic of rat, but not mouse or human, class I molecules (Rothermel et al 1993). RT1.M3 shares Leu219 and Asn220 with other rat and nearly all mouse class I molecules (Rada et al 1990;Watts et al 1989), whereas H2-M1, M2, M3, and M5 have a sequence more like the consensus Arg-Asp of HLA molecules (Bjorkman and Parham 1990).…”

Sequence, expression, and mapping of a rat Mhc class I b gene

“…Genomic fine mapping of the LW2 gene was achieved by polymerase chain reaction (PCR) with specific primers (see below), using genomic DNA of RT1 congenic rat strains LEW/Gun (RTll), LEW.1W/Gun (RT1,), LEW. 1R14/Won (RTlr14), LEWl.IR15/Won (RTlr15), and LEW.ILM1/ Won (RTllml; Rothermel et al 1993). PCR conditions…”

“…LW2 cDNA was cloned into the p164/7 plasmid, which carries the H-2K b promoter and a poly(A) site (R/Jther et al 1988). This construct was cotransfected with the neomycin resistance gene into mouse Ltk-fibroblasts, using the calcium phosphate precipitation method (Rothermel et al 1993). After selection with geneticin (Gibco BRL, Eggenstein, Germany), stable transfectant clones were established and analyzed by flow cytometry (FACScan, Becton Dickinson, Heidelberg) with the mouse monoclonal antibody (mAb) MRC OX18 specific for the rat class I antigens (Camon, Wiesbaden, Germany).…”