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NBS1-CtIP-mediated DNA end resection suppresses cGAS binding to micronuclei
Salim Abdisalaam1, Shibani Mukherjee1, Souparno Bhattacharya1
1Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Abstract:
Cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) is activated in cells with defective DNA damage repair and signaling (DDR) factors, but a direct role for DDR factors in regulating cGAS activation in response to micronuclear DNA is still poorly understood. Here, we provide novel evidence that Nijmegen breakage syndrome 1 (NBS1) protein, a well-studied DNA double-strand break (DSB) sensor-in coordination with Ataxia Telangiectasia Mutated (ATM), a protein kinase, and Carboxy-terminal binding protein 1 interacting protein (CtIP), a DNA end resection factor-functions as an upstream regulator that prevents cGAS from binding micronuclear DNA. When NBS1 binds to micronuclear DNA via its fork-head-associated domain, it recruits CtIP and ATM via its N- and C-terminal domains, respectively. Subsequently, ATM stabilizes NBS1's interaction with micronuclear DNA, and CtIP converts DSB ends into single-strand DNA ends; these two key events prevent cGAS from binding micronuclear DNA. Additionally, by using a cGAS tripartite system, we show that cells lacking NBS1 not only recruit cGAS to a major fraction of micronuclear DNA but also activate cGAS in response to these micronuclear DNA. Collectively, our results underscore how NBS1 and its binding partners prevent cGAS from binding micronuclear DNA, in addition to their classical functions in DDR signaling.
Insights
Nijmegen breakage syndrome 1 (NBS1) protein prevents cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) from binding micronuclear DNA. NBS1, along with ATM and CtIP, acts upstream to regulate cGAS activation in DNA damage repair.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- Cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) activation is linked to defects in DNA damage repair and signaling (DDR) factors.
- The precise role of DDR factors in regulating cGAS activation by micronuclear DNA remains unclear.
Purpose of the Study:
- To investigate the role of Nijmegen breakage syndrome 1 (NBS1) protein and its associated factors in regulating cGAS activation in response to micronuclear DNA.
- To elucidate the mechanism by which NBS1 prevents cGAS from binding to micronuclear DNA.
Main Methods:
- Utilized a cGAS tripartite system to assess cGAS activation.
- Investigated protein interactions between NBS1, ATM, and CtIP in the context of micronuclear DNA.
- Analyzed the binding of NBS1 to micronuclear DNA and its effect on DNA end resection.
Main Results:
- NBS1 protein, in coordination with ATM and CtIP, functions as an upstream regulator preventing cGAS binding to micronuclear DNA.
- NBS1 recruits ATM and CtIP to micronuclear DNA, where ATM stabilizes NBS1 binding and CtIP processes DNA ends, collectively inhibiting cGAS interaction.
- Cells lacking NBS1 exhibit increased cGAS recruitment to and activation by micronuclear DNA.
Conclusions:
- NBS1 and its partners ATM and CtIP play a crucial role in preventing aberrant cGAS activation by micronuclear DNA.
- These findings reveal a novel function of NBS1 beyond its canonical role in DNA double-strand break repair signaling.
- The study highlights the intricate interplay between DNA damage response pathways and innate immune signaling.
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