Generation of MHC Class II Diversity by Intra‐ and Intergenic Recombination

The occurrence and significance of recombination events in the generation of MHC class II diversity were discussed. Evidence that intragenic recombination has contributed to the generation of allelic diversity at a DRB locus in the moose was presented. Intergenic recombination (i.e. exchange of sequence information between nonallelic genes) is expected to be rare and only to play a minor role in the generation of class II diversity. Exchange of sequence information between the major isotypic forms of class II genes (DQ, DR and DP) is restricted to a segment encoding a major part of the a-helical region of polymorphic class II beta-chains. In this segment there is no or only weak locus divergence and the frequency of synonymous substitutions between nonallelic genes (DQB vs. DRB) within species is remarkably low, implying that exchange of sequence information has occurred repeatedly during the course of evolution.

[1]  J. Klein,et al.  The molecular descent of the major histocompatibility complex. , 1993, Annual review of immunology.

[2]  L. Andersson,et al.  Exon encoding the antigen-binding site of MHC class II beta-chains is divided into two subregions with different evolutionary histories. , 1992, Journal of immunology.

[3]  L. Andersson,et al.  Cloning and sequence analysis of 14 DRB alleles of the bovine major histocompatibility complex by using the polymerase chain reaction. , 2009, Animal genetics.

[4]  H. Erlich,et al.  Allelic diversity is generated by intraexon sequence exchange at the DRB1 locus of primates. , 1991, Proceedings of the National Academy of Sciences of the United States of America.

[5]  F. Bonhomme,et al.  Amplification of major histocompatibility complex class II gene diversity by intraexonic recombination. , 1991, Proceedings of the National Academy of Sciences of the United States of America.

[6]  J. H. Brown.  A hypothetical model of the foreign antigen binding site of Class II histocompatibility molecules , 1988, Nature.

[7]  C. Dieckmann,et al.  Preferential recombination between GC clusters in yeast mitochondrial DNA. , 1987, The EMBO journal.

[8]  J. B. Walsh,et al.  Sequence-dependent gene conversion: can duplicated genes diverge fast enough to escape conversion? , 1987, Genetics.

[9]  F. Bach,et al.  Polymorphism of human Ia antigens generated by reciprocal intergenic exchange between two DR β loci , 1986, Nature.

[10]  B. Mach,et al.  Polymorphism of human Ia antigens: gene conversion between two DR β loci results in a new HLA-D/DR specificity , 1986, Nature.

[11]  P. A. Peterson,et al.  The Eb beta gene may have acted as the donor gene in a gene conversion‐like event generating the Abm 12 beta mutant. , 1984, EMBO Journal.