Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2015 Mar;117(2-3):182-193.
doi: 10.1016/j.pbiomolbio.2014.12.004. Epub 2015 Jan 7.

Envisioning the dynamics and flexibility of Mre11-Rad50-Nbs1 complex to decipher its roles in DNA replication and repair

Julien Lafrance-Vanasse  1 , Gareth J Williams  1 , John A Tainer  2
Affiliations
Review

Envisioning the dynamics and flexibility of Mre11-Rad50-Nbs1 complex to decipher its roles in DNA replication and repair

Julien Lafrance-Vanasse et al. Prog Biophys Mol Biol. 2015 Mar.

Abstract

The Mre11-Rad50-Nbs1 (MRN) complex is a dynamic macromolecular machine that acts in the first steps of DNA double strand break repair, and each of its components has intrinsic dynamics and flexibility properties that are directly linked with their functions. As a result, deciphering the functional structural biology of the MRN complex is driving novel and integrated technologies to define the dynamic structural biology of protein machinery interacting with DNA. Rad50 promotes dramatic long-range allostery through its coiled-coil and zinc-hook domains. Its ATPase activity drives dynamic transitions between monomeric and dimeric forms that can be modulated with mutants modifying the ATPase rate to control end joining versus resection activities. The biological functions of Mre11's dual endo- and exonuclease activities in repair pathway choice were enigmatic until recently, when they were unveiled by the development of specific nuclease inhibitors. Mre11 dimer flexibility, which may be regulated in cells to control MRN function, suggests new inhibitor design strategies for cancer intervention. Nbs1 has FHA and BRCT domains to bind multiple interaction partners that further regulate MRN. One of them, CtIP, modulates the Mre11 excision activity for homologous recombination repair. Overall, these combined properties suggest novel therapeutic strategies. Furthermore, they collectively help to explain how MRN regulates DNA repair pathway choice with implications for improving the design and analysis of cancer clinical trials that employ DNA damaging agents or target the DNA damage response.

Keywords: Allostery; Conformational change; CtIP; Double strand break repair; Dynamics; Mre11-Rad50-Nbs1.

PubMed Disclaimer

Figures

Figure 1
Figure 1. Architecture of the Mre11-Rad50-Nbs1 complex with its partner CtIP
The Rad50 dimer is in orange and yellow (for each monomer) and the coiled-coils are represented as helices extending towards the zinc-hook. The Mre11 dimer is shown in blue and dark blue and interacts with Nbs1, shown in green (different shades represent the different domains). Nbs1 interacts with CtIP through its FHA domain (dark green). Interaction with ATM is shown by a black arrow. The dotted lines represent disordered protein linkers.
Figure 2
Figure 2. Model of MRN’s functions in DSB repair
(A) MRN first detects and interacts with the DNA end. (B) If the process goes into HRR, MRN moves away from the break (shown with an arrow) and recruits CtIP. (C) CtIP induces changes in MRN leading to an open complex capable of nuclease activities. (D) After an initial endonuclease cut, MRN resects from 3′ to 5′ towards the DSB, with its exonuclease activity, while EXO1/BLM or DNA2/BLM resects from 5′ to 3′. (E) In NHEJ or HRR, the DNA tethering functions of MRN can be used. Color-coding is the same as in Figure 1.
Figure 3
Figure 3. Long-range allostery is a crucial feature of Rad50
Top: ATP binding induces rotation of the C-lobe relative to the N-lobe of Rad50’s head domain. This is communicated to the zinc-hook domain through the coiled-coils, possibly by helix sliding. Bottom: schematic of Rad50’s sequence with arrows depicting segments of flexibility and dynamics.
Figure 4
Figure 4. Rad50 ATP binding and hydrolysis controls its conformational state and pathway choice
(A) Crystal structures showing the Mre11-Rad50 head without nucleotide (top, PDB 3QG5) and bound to nucleotide (bottom, PDB 3AV0). Mre11 (surface representation) and Rad50 (cartoon representation) are colored by subdomains as indicated (the color of the font matches the color of the domain). In the nucleotide-free state, Rad50 monomers are flexible and conformationally sample the closed state, as indicated by dashed-arrows. (B) Top: Crystal structures of P. furiosus Rad50 without nucleotide (PDB 3QKS) show a core cavity (green surface) adjacent to the signature motif (magenta) that remodels upon ATP-binding. The L802W mutation (PDB 4NCH) partially fills the core cavity, destabilizing the ATP-bound closed state. In contrast, the R805E variant (PDB 4NCI) destabilizes the Rad50 monomer resulting in a stabilization of the ATP-bound closed state. Bottom: The effects of the mutations compared to wildtype Rad50 on Mre11-Rad50 conformational states and activities are depicted.
Figure 5
Figure 5. Flexibility and dynamics are part of Mre11 and Nbs1’s structures
Top: Structure of MRN highlighting flexible segments (arrows). Color-coding is the same as Figure 1, except Rad50 is gray and the capping domain of Mre11 is cyan. Bottom: schematic of Mre11 and Nbs1’s sequences with arrows depicting segments of flexibility and dynamics. Dashed lines and arrows represent intrinsically disordered segments.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Al-Ahmadie H, Iyer G, Hohl M, Asthana S, Inagaki A, Schultz N, Hanrahan AJ, Scott SN, Brannon AR, McDermott GC, Pirun M, Ostrovnaya I, Kim P, Socci ND, Viale A, Schwartz GK, Reuter V, Bochner BH, Rosenberg JE, Bajorin DF, Berger MF, Petrini JHJ, Solit DB, Taylor BS. Synthetic Lethality in ATM-Deficient RAD50-Mutant Tumors Underlies Outlier Response to Cancer Therapy. Cancer Discov. 2014;4:1014–1021. doi: 10.1158/2159-8290.CD-14-0380. - DOI - PMC - PubMed
    1. Anderson DE, Trujillo KM, Sung P, Erickson HP. Structure of the Rad50 x Mre11 DNA repair complex from Saccharomyces cerevisiae by electron microscopy. J Biol Chem. 2001;276:37027–37033. doi: 10.1074/jbc.M106179200. - DOI - PubMed
    1. Bhaskara V, Dupré A, Lengsfeld B, Hopkins BB, Chan A, Lee JH, Zhang X, Gautier J, Zakian V, Paull TT. Rad50 adenylate kinase activity regulates DNA tethering by Mre11/Rad50 complexes. Mol Cell. 2007;25:647–661. doi: 10.1016/j.molcel.2007.01.028. - DOI - PMC - PubMed
    1. Boisvert F-M, Déry U, Masson JY, Richard S. Arginine methylation of MRE11 by PRMT1 is required for DNA damage checkpoint control. Genes Dev. 2005;19:671–676. doi: 10.1101/gad.1279805. - DOI - PMC - PubMed
    1. Cahill D, Carney JP. Dimerization of the Rad50 protein is independent of the conserved hook domain. Mutagenesis. 2007;22:269–274. doi: 10.1093/mutage/gem011. - DOI - PubMed

Publication types

MeSH terms