Senataxin promotes recombination fidelity during antigen receptor gene diversification

Immunoglobulin (Ig) and T cell receptor (TCR) V(D)J gene recombination relies on non-homologous end-joining (NHEJ), which repairs DNA double-strand breaks (DSBs) introduced by the RAG1/2 nuclease complex. Functional redundancies exist between NHEJ and the ATM kinase-dependent chromatin DSB response, likely masking the activity of additional factors. Here, we performed parallel targeted CRISPR-Cas9 screens in pro-B cells and found that Senataxin (SETX) participates in V(D)J recombination. We find that SETX supports V(D)J recombination, particularly in condition of ATM kinase inhibition or XLF deficiency. Furthermore, we show that SETX suppresses the formation of aberrant coding end-to-signal end hybrid joints during V(D)J recombination and prevents the aberrant joining of AID-induced DNA ends during Ig heavy chain class switching, revealing an essential role for SETX in promoting recombination fidelity during antigen receptor gene diversification. Bone marrow cells proficient or deficient in SETX and v-Abl pro-B cells deficient in p53 alone or in combination with XLF, XRCC4, SETX, or XLF/SETX deficiency were isolated for genomic DNA and subjected to LAM-HTGTS JoinT-seq DNA junction mapping using Jkappa1 coding end bait primers as described PMID: 38412274.