Coordinate regulation of RAG1 and RAG2 by cell type-specific DNA elements 5 ' of RAG2

RAG1 and RAG2 are essential for V(D)J recombination and Lymphocyte developm ent. These genes are thought to encode a transposase derived from a mobile genetic element that was inserted into the vertebrate genome 450 million ye ars ago. The regulation of RAG1 and RAG2 was investigated in vivo with bact erial artificial chromosome (BAC) transgenes containing a fluorescent indic ator. Coordinate expression of RAG1 and RAG2 in B and T cells was found to be regulated by distinct genetic elements found on the 5' side of the RAG2 gene. This observation suggests a mechanism by which asymmetrically dispose d cis DNA elements could influence the expression of the primordial transpo son and thereby capture RAGs for vertebrate evolution.