Rch1, a Protein that Specifically Interacts with the RAG-1 Recombination-Activating Protein

RAG1 and RAG2 are lymphoid-specific genes that together induce V(D)J recombinase activity in a variety of nonlymphoid cell types. While no other lymphoid-specific factors are required to induce recombination, other factors with more widespread expression patterns have been implicated in the reaction. However, none of these factors have been cloned, and their relationship to the RAG proteins is unclear. Using the yeast two-hybrid assay, we have identified RCH1, a gene encoding a protein of molecular weight 58,000 that interacts specifically with RAG-1. The predicted Rch1 protein sequence is 47% identical to yeast SRP1, a protein associated with the nuclear envelope. A truncated form of Rch1, which retains the ability to interact with RAG-1, reduces V(D)J recombination activity in HeLa cells.