Structure of class II genes in wild mouse Mus saxicola: functional and evolutionary implications.
Class II beta genes have been characterized from Mus saxicola, a wild mouse which diverged five millions years ago from the house mouse. The nucleotide sequences of the exons 2 and 3 of E beta 1, A beta 2 and E beta 2 genes have been determined in order to define the molecular mechanisms of interspecies variability. The E beta 1 and A beta 1 (J. X. She, personal communication) genes from Mus saxicola display extensive sequence variability in exon 2 when compared to those of the house mouse, in association with the variability of residues probably involved in antigen binding. On the other hand, most putative T cell contact residues from the I-E beta chain, and to a lesser extent from the I-A beta chain, were found conserved in mice. T cell contact residues from Mus saxicola I-A beta and I-E beta chains are identical to those of the b and q, and of the k haplotypes of the house mouse, respectively. Comparisons performed with A beta 2 and E beta 2 genes revealed that both are highly conserved and, in contrast to A beta 1 and E beta 1 genes, that a strong selective pressure for conservation occurs in the A beta 2 second exon. The different aspects of A beta 2 and E beta 2 genes evolution may correlate with the original function of their products. Comparisons of the intervening sequences revealed that the repeated motifs of the hotspot region present in the E beta 1b gene are also conserved in Mus saxicola. Recombinations may have occurred, in some cases in association with chi-like sequences.
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Institut Pasteur, Paris National Institutes of Health, Bethesda.
Jouvin-Marche
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LeGuern
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Marche
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D000595:Amino Acid Sequence; D000818:Animals; D000835:Animals, Wild / Q000235:genetics / Q000276:immunology*; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D014644:Genetic Variation; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009115:Muridae / Q000235:genetics / Q000276:immunology*; D012689:Sequence Homology, Nucleic Acid; D013329:Structure-Activity Relationship
D000949:Histocompatibility Antigens Class II