Characterization of the recombinase activating gene-1 and 2 locus in the Japanese pufferfish, Fugu rubripes

The recombinase activating genes (RAGI and RAG2) encode nuclear proteins th at directly mediate the mechanism V(D)J recombination process that occurs i n T- and B-lymphocytes. The expression of RA GI and RAG2 is required for th e proper development of maturing lymphocytes. To identify evolutionary cons erved regulatory regions adjacent to both genes we isolated and sequenced a cosmid clone containing 43 kb of genomic DNA of the Japanese pufferfish, F ugu rubripes. Fugu has a haploid genome of 400 Mb and contains the same num ber of genes as the genome of higher vertebrates. With low abundance of rep etitive DNA, the genome of the pufferfish has shown to be ideal for compara tive genomics. We found three complete genes, RAGI, RAG2 and ACS (a possibl e homologue of the plant I-aminocyclopropane-carboxylate synthase gene). Th ere is also the 5' exon of a prohormone convertase gene, possibly PACE4. Th e genetic structure of both RAGI and RAG2 is identical to that found in oth er fish, but the size of the intergenic region is smaller in Fugu. Expressi on analysis by RT-PCR shows the presence of RAG transcripts in kidney of ad ult Fugu. The human ACS was identified in a cosmid assigned to chromosome 1 1p11, which is close to the location of the RAGs (11p12). This indicates co nservation of linkage between human and pufferfish. (C) 2000 Elsevier Scien ce B.V. All rights reserved.