# ATM Function During V(D)J Recombination

> **NIH NIH R01** · UNIVERSITY OF ALABAMA AT BIRMINGHAM · 2023 · $371,250

## Abstract

Abstract
Lymphocyte antigen receptor gene assembly occurs through the V(D)J recombination reaction. This reaction
is initiated when the RAG-1 and RAG-2 proteins, which form the RAG endonuclease, introduces two DNA
double strand breaks (DSBs) at the border of two recombining gene segments and their associated V, D or J
gene segments. This results in the formation of a coding end and a signal end at each DSB. The coding ends
must be joined to form a coding join and the signal ends joined to form a signal join. Also, as a single
individual can make up to 60,000,000 RAG DSBs in an hour in developing B and T cells, pathways must be in
place to prevent un-repaired RAG DSBs from being aberrantly repaired, forming potentially transforming
chromosomal deletions and translocations. The non-homologous end-joining pathway of DNA DSB repair
joins DNA DSBs generated by RAG cleavage. NHEJ relies on four core NHEJ factors, XRCC4, DNA Ligase
IV, Ku70 and Ku80. However, there are other non-core NHEJ factors that function during the NHEJ-mediated
repair of RAG DSBs. For example, coding join formation relies on the ncNHEJ factor, Artemis, which is
endonuclease that opens the hairpin-sealed coding ends generated by RAG cleavage. Artemis is not required
for joining signal ends. In addition, there are other ncNHEJ factors that are not themselves required for RAG
DSB repair, but that likely effect the efficiency of RAG DSB repair or function to prevent aberrant repair of RAG
DSBs that are not joined efficiently. Identifying ncNHEJ factors has been challenging given that their deletion
does not often lead to a demonstrable defect in the repair of RAG DSBs. However, recent studies have
established that combined deficiencies of putative ncNHEJ factors can lead to demonstrable defects in RAG
DSBs repair. This has been a powerful candidate-based approach for identifying several ncNHEJ factors and
elucidating their mechanisms of action in NHEJ-mediated DSB repair and DNA damage responses (DDR).
Indeed, using this type of approach, we have identified a novel ncNHEJ protein, modulator of retroviral
infection (MRI), that binds through its N- and C-terminus to a functionally diverse set of NHEJ and DDR
proteins. We believe that MRI functions as an adaptor during several steps of NHEJ-mediated repair of RAG
DSBs and during the DDR to RAG DSBs. Here we propose a novel unbiased screening approach to identify
the network of ncNHEJ factors that function during RAG DSB repair. We also propose to elucidate the
mechanisms of action of these ncNHEJ factors focusing initially on the novel ncNHEJ factor, MRI, that we
recently discovered that functions in RAG DSB repair. These studies will reveal novel activities required for the
NHEJ-mediated repair of RAG DSBs. These activities will likely be generally relevant to NHEJ in other tissues
and to our understanding to DNA repair defects that lead to genome evolution in cancers.

## Key facts

- **NIH application ID:** 10518400
- **Project number:** 5R01AI074953-17
- **Recipient organization:** UNIVERSITY OF ALABAMA AT BIRMINGHAM
- **Principal Investigator:** Barry P Sleckman
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $371,250
- **Award type:** 5
- **Project period:** 2008-12-02 → 2024-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10518400

## Citation

> US National Institutes of Health, RePORTER application 10518400, ATM Function During V(D)J Recombination (5R01AI074953-17). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10518400. Licensed CC0.

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