Mammalian cells have evolved a common DNA damage response (DDR) that sustains cellular function, maintains genomic integrity, and suppresses malignant transformation. In pre-B cells, DNA double-strand breaks (DSBs) induced at Igκ loci by the Rag1/Rag2 (RAG) endonuclease engage this DDR to modulate transcription of genes that regulate lymphocyte-specific processes. We previously reported that RAG DSBs induced at one Igκ allele signal through the ataxia telangiectasia mutated (ATM) kinase to feedback-inhibit RAG expression and RAG cleavage of the other Igκ allele. In this article, we show that DSBs induced by ionizing radiation, etoposide, or bleomycin suppress Rag1 and Rag2 mRNA levels in primary pre-B cells, pro-B cells, and pro-T cells, indicating that inhibition of Rag1 and Rag2 expression is a prevalent DSB response among immature lymphocytes. DSBs induced in pre-B cells signal rapid transcriptional repression of Rag1 and Rag2, causing downregulation of both Rag1 and Rag2 mRNA, but only Rag1 protein. This transcriptional inhibition requires the ATM kinase and the NF-κB essential modulator protein, implicating a role for ATM-mediated activation of canonical NF-κB transcription factors. Finally, we demonstrate that DSBs induced in pre-B cells by etoposide or bleomycin inhibit recombination of Igκ loci and a chromosomally integrated substrate. Our data indicate that immature lymphocytes exploit a common DDR signaling pathway to limit DSBs at multiple genomic locations within developmental stages wherein monoallelic Ag receptor locus recombination is enforced. We discuss the implications of our findings for mechanisms that orchestrate the differentiation of monospecific lymphocytes while suppressing oncogenic Ag receptor locus translocations.
This work was supported by the Training Program in Rheumatic Diseases of the University of Pennsylvania (Grant T32 AR007442 to M.R.F.), the National Research Service Award (Grant F31 CA183551 to M.R.F.), the Training Program in Cell and Molecular Biology of the University of Pennsylvania (Grant GM007229 T32 to A.R.-R), the National Institutes of Health (Grant R37 AI32524 to D.G.S.; R01 Grant AI112621 to C.H.B.), and the Department of Pathology and Laboratory Medicine, Children’s Hospital of Philadelphia (to C.H.B.).
The online version of this article contains supplemental material.
Abbreviations used in this article:
- Ag receptor
- ataxia telangiectasia mutated
- bone marrow
- DNA damage response
- double-strand break
- ethynyl uridine
- B cell–specific transcriptional enhancer of the Rag1/Rag2 locus
- ionizing radiation
- New England Biolabs
- nonhomologous end-joining
- real-time PCR
- recombination signal sequence
- Received September 22, 2016.
- Accepted January 16, 2017.
- Copyright © 2017 by The American Association of Immunologists, Inc.