Full Length RAG2 Expression Enhances the DNA Damage Response in Pre-B Cells

Abstract

Abstract V(D)J recombination of lymphocyte antigen receptor genes occurs via formation of DNA double strand breaks (DSBs) through activity of RAG1 and RAG2. The co-existence of RAG-independent DNA DSBs generated by genotoxic stressors potentially increases the risk of incorrect repair and chromosomal abnormalities. It is not known how developing immune cells respond to DNA damage in a manner that achieves optimal balance between continued cell development with genomic integrity. Studies from our lab show full length RAG2 exports from the nucleus and enriches at the centrosome within minutes following DNA damage in pre-B cells, exhibiting a response of RAG2 upon DNA damage. The exact mechanism by which RAG2 relocalization occurs is not known, however, mass spectrometry results identified three centrosomal proteins that interact with RAG2 strictly in the presence of DNA DSBs. To determine how RAG2 may affect cell viability upon genotoxic stress, we examined various cell responses versus time following irradiation of cells expressing either full length or mutants of RAG2. Our results indicate that RAG2 plays an active role in bolstering DNA damage responses to genotoxic stresses. Specifically, cells expressing full length RAG2, versus mutant forms, show an increase in the ability to cull damaged cells from the cell population, with evidence of more robust cell division several days after cells were subjected to genotoxic insult. Overall, we propose that while RAG2 functions to cleave DNA during V(D)J recombination, it also performs an alternate function to reinforce the cell’s response to DNA damage, thus facilitating continued development of immune cells to help generate a robust immune system.