EVOLUTIONARY CONSERVATION AND MOLECULAR-CLONING OF THE RECOMBINASE ACTIVATING GENE-1

A 700-bp fragment of the recombinase activating gene 1 (RAG-1) was cloned from several evolutionarily distant (sandbar shark, paddlefish, goldfish, axolotl and pig) species using PCR. The nucleotide and deduced amino acid sequences revealed a highly conserved region that has remained essentially unaltered during 400 million years of evolution; e.g, shark and human sequences were 75% identical at the nucleic acid level and 87% as protein. The RAG-I mRNA levels in the shark were analyzed using semi-quantitative PCR to reveal expression patterns contrary to normal mammalian expression. These results establish that the genetic mechisms for Ig gene rearrangement are present in all extant gnathanstomes. (C) 1994 Academic Press, Inc.