EXPRESSION AND V(D)J RECOMBINATION ACTIVITY OF MUTATED RAG-1 PROTEINS

The products of the RAG-1 and RAG-2 genes ([1], [2]) are essential for the recombination of the DNA encoding the antigen receptors of the de veloping immune system. Little is known of the specific role these gen es play. We have explored the sequences encoding mouse RAG-1 by deleti ng large parts of the gene and by introducing local sequence changes. We find that a RAG-1 gene with 40% of the coding region deleted still retains its recombination function. In addition, a series of small del etions within the strongly conserved remaining 60% of the coding regio n was tested. Nine out of ten of these prove unable to provide RAG-1 a ctivity, but one is quite active. Certain peptide sequences were also specifically targeted for mutagenesis. The RAG-1 protein generated fro m this expression system is transported to the nucleus and is degraded with a 15 minute half-life. The fate of the proteins made by the dele tion mutants were also assessed. Transport of RAG-1 protein to the nuc leus was found even with the most extensive deletions studied. The fun ctionality of the deleted proteins is discussed with relation to an al ignment of RAG-1 sequences from five animal species.