Faculty Opinions recommendation of MRN complex function in the repair of chromosomal Rag-mediated DNA double-strand breaks.

The Mre11–Rad50–Nbs1 (MRN) complex functions in the repair of DNA double-strand breaks (DSBs) by homologous recombination (HR) at postreplicative stages of the cell cycle. During HR, the MRN complex functions directly in the repair of DNA DSBs and in the initiation of DSB responses through activation of the ataxia telangiectasia-mutated (ATM) serine-threonine kinase. Whether MRN functions in DNA damage responses before DNA replication in G0/G1 phase cells has been less clear. In developing G1-phase lymphocytes, DNA DSBs are generated by the Rag endonuclease and repaired during the assembly of antigen receptor genes by the process of V(D)J recombination. Mice and humans deficient in MRN function exhibit lymphoid phenotypes that are suggestive of defects in V(D)J recombination. We show that during V(D)J recombination, MRN deficiency leads to the aberrant joining of Rag DSBs and to the accumulation of unrepaired coding ends, thus establishing a functional role for MRN in the repair of Rag-mediated DNA DSBs. Moreover, these defects in V(D)J recombination are remarkably similar to those observed in ATM-deficient lymphocytes, suggesting that ATM and MRN function in the same DNA DSB response pathways during lymphocyte antigen receptor gene assembly.

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hSSB1 rapidly binds at the sites of DNA double-strand breaks and is required for the efficient recruitment of the MRN complex

Nucleic Acids Research ◽

10.1093/nar/gkq1098 ◽

2010 ◽

Vol 39 (5) ◽

pp. 1692-1702 ◽

Cited By ~ 43

Author(s):

Derek J. Richard ◽

Kienan Savage ◽

Emma Bolderson ◽

Liza Cubeddu ◽

Sairei So ◽

...

Keyword(s):

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Mrn Complex

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A Survey of Reported Disease-Related Mutations in the MRE11-RAD50-NBS1 Complex

Cells ◽

10.3390/cells9071678 ◽

2020 ◽

Vol 9 (7) ◽

pp. 1678 ◽

Cited By ~ 2

Author(s):

Samiur Rahman ◽

Marella D. Canny ◽

Tanner A. Buschmann ◽

Michael P. Latham

Keyword(s):

Genomic Stability ◽

Nijmegen Breakage Syndrome ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Response Factors ◽

Strand Breaks ◽

Mrn Complex ◽

Damage Response ◽

Biochemical Level

The MRE11-RAD50-NBS1 (MRN) protein complex is one of the primary vehicles for repairing DNA double strand breaks and maintaining the genomic stability within the cell. The role of the MRN complex to recognize and process DNA double-strand breaks as well as signal other damage response factors is critical for maintaining proper cellular function. Mutations in any one of the components of the MRN complex that effect function or expression of the repair machinery could be detrimental to the cell and may initiate and/or propagate disease. Here, we discuss, in a structural and biochemical context, mutations in each of the three MRN components that have been associated with diseases such as ataxia telangiectasia-like disorder (ATLD), Nijmegen breakage syndrome (NBS), NBS-like disorder (NBSLD) and certain types of cancers. Overall, deepening our understanding of disease-causing mutations of the MRN complex at the structural and biochemical level is foundational to the future aim of treating diseases associated with these aberrations.

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DNA damage signaling in response to double-strand breaks during mitosis

The Journal of Cell Biology ◽

10.1083/jcb.200911156 ◽

2010 ◽

Vol 190 (2) ◽

pp. 197-207 ◽

Cited By ~ 189

Author(s):

Simona Giunta ◽

Rimma Belotserkovskaya ◽

Stephen P. Jackson

Keyword(s):

Dna Damage ◽

Mitotic Cell ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Histone H2ax ◽

Mrn Complex ◽

Dna Damage Signaling ◽

Dependent Protein ◽

Mitotic Cells

The signaling cascade initiated in response to DNA double-strand breaks (DSBs) has been extensively investigated in interphase cells. Here, we show that mitotic cells treated with DSB-inducing agents activate a “primary” DNA damage response (DDR) comprised of early signaling events, including activation of the protein kinases ataxia telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNA-PK), histone H2AX phosphorylation together with recruitment of mediator of DNA damage checkpoint 1 (MDC1), and the Mre11–Rad50–Nbs1 (MRN) complex to damage sites. However, mitotic cells display no detectable recruitment of the E3 ubiquitin ligases RNF8 and RNF168, or accumulation of 53BP1 and BRCA1, at DSB sites. Accordingly, we found that DNA-damage signaling is attenuated in mitotic cells, with full DDR activation only ensuing when a DSB-containing mitotic cell enters G1. Finally, we present data suggesting that induction of a primary DDR in mitosis is important because transient inactivation of ATM and DNA-PK renders mitotic cells hypersensitive to DSB-inducing agents.

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Functional and structural insights into the MRX/MRN complex, a key player in recognition and repair of DNA double-strand breaks

Computational and Structural Biotechnology Journal ◽

10.1016/j.csbj.2020.05.013 ◽

2020 ◽

Vol 18 ◽

pp. 1137-1152 ◽

Cited By ~ 3

Author(s):

Renata Tisi ◽

Jacopo Vertemara ◽

Giuseppe Zampella ◽

Maria Pia Longhese

Keyword(s):

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Mrn Complex ◽

Structural Insights

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hSSB1 interacts directly with the MRN complex stimulating its recruitment to DNA double-strand breaks and its endo-nuclease activity

Nucleic Acids Research ◽

10.1093/nar/gkq1340 ◽

2011 ◽

Vol 39 (9) ◽

pp. 3643-3651 ◽

Cited By ~ 49

Author(s):

Derek J. Richard ◽

Liza Cubeddu ◽

Aaron J. Urquhart ◽

Amanda Bain ◽

Emma Bolderson ◽

...

Keyword(s):

Nuclease Activity ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Mrn Complex

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DROSHA is recruited to DNA damage sites by the MRN complex to promote non-homologous end-joining

Journal of Cell Science ◽

10.1242/jcs.249706 ◽

2021 ◽

pp. jcs.249706

Author(s):

Matteo Cabrini ◽

Marco Roncador ◽

Alessandro Galbiati ◽

Lina Cipolla ◽

Antonio Maffia ◽

...

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

End Joining ◽

Strand Breaks ◽

Mrn Complex ◽

Break Site ◽

Non Homologous End Joining ◽

Dna Ends

The DNA damage response (DDR) is the signaling cascade that recognizes DNA double-strand breaks (DSB) and promotes their resolution via the DNA repair pathways of Non-Homologous End Joining (NHEJ) or Homologous Recombination (HR). We and others have shown that DDR activation requires DROSHA. However, whether DROSHA exerts its functions by associating with damage sites, what controls its recruitment and how DROSHA influences DNA repair, remains poorly understood. Here we show that DROSHA associates to DSBs independently from transcription. Neither H2AX, nor ATM nor DNA-PK kinase activities are required for its recruitment to break site. Rather, DROSHA interacts with RAD50 and inhibition of MRN by Mirin treatment abolishes this interaction. MRN inactivation by RAD50 knockdown or mirin treatment prevents DROSHA recruitment to DSB and, as a consequence, also 53BP1 recruitment. During DNA repair, DROSHA inactivation reduces NHEJ and boosts HR frequency. Indeed, DROSHA knockdown also increase the association of downstream HR factors such as RAD51 to DNA ends. Overall, our results demonstrate that DROSHA is recruited at DSBs by the MRN complex and direct DNA repair toward NHEJ.

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MRE11-RAD50-NBS1 promotes Fanconi Anemia R-loop suppression at transcription–replication conflicts

Nature Communications ◽

10.1038/s41467-019-12271-w ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 16

Author(s):

Emily Yun-Chia Chang ◽

Shuhe Tsai ◽

Maria J. Aristizabal ◽

James P. Wells ◽

Yan Coulombe ◽

...

Keyword(s):

Dna Replication ◽

Fanconi Anemia ◽

Genome Instability ◽

Double Strand Breaks ◽

Dna Double Strand Breaks ◽

Strand Breaks ◽

Mrn Complex ◽

Genome Wide ◽

A Genome ◽

Dna Replication Stress

Abstract Ectopic R-loop accumulation causes DNA replication stress and genome instability. To avoid these outcomes, cells possess a range of anti-R-loop mechanisms, including RNaseH that degrades the RNA moiety in R-loops. To comprehensively identify anti-R-loop mechanisms, we performed a genome-wide trigenic interaction screen in yeast lacking RNH1 and RNH201. We identified >100 genes critical for fitness in the absence of RNaseH, which were enriched for DNA replication fork maintenance factors including the MRE11-RAD50-NBS1 (MRN) complex. While MRN has been shown to promote R-loops at DNA double-strand breaks, we show that it suppresses R-loops and associated DNA damage at transcription–replication conflicts. This occurs through a non-nucleolytic function of MRE11 that is important for R-loop suppression by the Fanconi Anemia pathway. This work establishes a novel role for MRE11-RAD50-NBS1 in directing tolerance mechanisms at transcription–replication conflicts.

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Repair pathway choice for double-strand breaks

Essays in Biochemistry ◽

10.1042/ebc20200007 ◽

2020 ◽

Vol 64 (5) ◽

pp. 765-777 ◽

Cited By ~ 2

Author(s):

Yixi Xu ◽

Dongyi Xu

Keyword(s):

Cell Cycle ◽

Double Strand Breaks ◽

Homologous Region ◽

Gene Repair ◽

Repair Pathway ◽

Dna Double Strand Breaks ◽

Environmental Radiation ◽

Strand Breaks ◽

Dna End Resection ◽

End Resection

Abstract Deoxyribonucleic acid (DNA) is at a constant risk of damage from endogenous substances, environmental radiation, and chemical stressors. DNA double-strand breaks (DSBs) pose a significant threat to genomic integrity and cell survival. There are two major pathways for DSB repair: nonhomologous end-joining (NHEJ) and homologous recombination (HR). The extent of DNA end resection, which determines the length of the 3′ single-stranded DNA (ssDNA) overhang, is the primary factor that determines whether repair is carried out via NHEJ or HR. NHEJ, which does not require a 3′ ssDNA tail, occurs throughout the cell cycle. 53BP1 and the cofactors PTIP or RIF1-shieldin protect the broken DNA end, inhibit long-range end resection and thus promote NHEJ. In contrast, HR mainly occurs during the S/G2 phase and requires DNA end processing to create a 3′ tail that can invade a homologous region, ensuring faithful gene repair. BRCA1 and the cofactors CtIP, EXO1, BLM/DNA2, and the MRE11–RAD50–NBS1 (MRN) complex promote DNA end resection and thus HR. DNA resection is influenced by the cell cycle, the chromatin environment, and the complexity of the DNA end break. Herein, we summarize the key factors involved in repair pathway selection for DSBs and discuss recent related publications.

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