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Deciphering & drugging DNA Repair

Sebastien Britton

Group Leader

The Deciphering & drugging DNA Repair lab aims at deciphering how human cells respond to DNA damage to identify and validate new druggable complexes for cancer treatment. Our landmark discoveries include alternative End-Joining (2004), mechanisms antagonizing Ku association to some DNA ends (2016, 2020), a new function for BRCA1 at centromeres (2014) and the characterization of Ku interactions with DNA repair factors (2018).

DNA repair controls the outcome of several anticancer therapies. As such there is a huge interest for novel small molecules modulating DNA repair. In the DDR lab, we decipher how cells respond to DNA damage, more specifically to the most harmful type, DNA Double-Strand Breaks (DSBs). We use the resulting knowledge to design and perform targeted and phenotypical based screens to identify new modulators of specific aspects of the DNA damage response. To achieve our goals, we rely on high- and super-resolution imaging, molecular and cell biology, genomics, small molecules screening, chemical probes and on multiple collaborations with structural biologists and chemists. We recently implemented in the lab several complementary approaches to decipher how biologically active small molecules act.


We currently study:
1. the interplay between DNA repair mechanisms. Two principal DSB repair mechanisms co-exist in human cells: Non-Homologous End Joining (NHEJ) and Homologous Recombination (HR). Using a new method for imaging NHEJ proteins, we recently discovered the main mechanism antagonizing NHEJ proteins association to special DSBs, thereby allowing HR to proceed. We established that these mechanisms are druggable and that their inhibition triggers toxic DNA repair events in response to some anticancer agents (Britton et al. 2013 J Cell Biol; Chanut, Britton et al. 2016 Nat commun; Britton, Chanut et al. 2020 Nucleic Acids Res). 

2. how DNA repair proteins associate on damaged chromatin. We recently characterized how the repair factors APLF and XLF associate with the NHEJ core protein Ku at DNA damage, thereby characterizing two new interaction interfaces at the functional and structural levels (Nemoz, Ropars, Frit et al. 2018 Nat Struct Mol Biol). We also investigate how the genomic context, such as heterochromatin and transcription, affect DNA repair and genome stability. Using laser micro-irradiation and live imaging, we discovered a novel mechanism promoting the exclusion of a large number of RNA-binding proteins from DNA damage sites, thereby preventing the local accumulation of R-loops (Britton, Dernoncourt et al. Nucleic Acids Res 2014). 

3. how stabilizing specific DNA structures triggers DNA damage. Small molecules stabilizing secondary DNA structures, such as G-quadruplexes (G4) ligands, trigger DNA damage (Zell et al. 2020 RSC Chem Biol). Through an unbiased genomic approach, we recently discovered that DNA topoisomerase 2 alpha is responsible for the production of DSB by several G4 ligands (Pipier et al. 2020 BioRxiv), including CX-5461 a molecule undergoing clinical trials in oncology. We also contributed to develop novel ligands of another secondary structure, the Three-way Junction, and established that they also trigger DNA damage by a mechanism that we are currently investigating (Duskova 2019 J Med Chem, Duskova et al. 2020 JACS).


Main Publications

Bossaert, Pipier et al. (2021). Transcription-associated topoisomerase 2α (TOP2A) activity is a major effector of cytotoxicity induced by G-quadruplex ligands. eLife.


Britton, Chanut et al. (2020) ATM antagonizes NHEJ proteins assembly and DNA-ends synapsis at single-ended DNA double strand breaks. Nucleic Acids Res.


Duskova et al. (2020) DNA Junction Ligands Trigger DNA Damage and Are Synthetic Lethal with DNA Repair Inhibitors in Cancer Cells. J. Am. Chem. Soc.

Nemoz, Ropars, Frit et al. (2018) XLF and APLF bind Ku80 at two remote sites to ensure DNA repair by non-homologous end joining. Nat. Struct. Mol. Biol.

Rozié et al. (2018) Alkyne-Tagged Analogue of Jaspine B: New Tool for Identifying Jaspine B Mode of Action. ChemBioChem


Bombarde et al. (2017) The DNA-Binding Polyamine Moiety in the Vectorized DNA Topoisomerase II Inhibitor F14512 Alters Reparability of the Consequent Enzyme-Linked DNA Double-Strand Breaks. Mol. Cancer Ther.


Chanut, Britton et al. (2016) Coordinated nuclease activities counteract Ku at single-ended DNA double-strand breaks. Nat. Commun.


Yuan, Britton et al. (2015) Single-stranded DNA oligomers stimulate error-prone alternative repair of DNA double-strand breaks through hijacking Ku protein Nucleic Acids Res.

Britton, Dernoncourt et al. (2014) DNA damage triggers SAF-A and RNA biogenesis factors exclusion from chromatin coupled to R-loops removal. Nucleic Acids Res.

High-resolution imaging of DNA Double-Strand Breaks (DSBs) in human cells treated with ionizing radiations in presence of a DDR inhibitor. Red: DSBs visualized with gammaH2AX; Green: Actin cytoskeleton; Blue: DNA.

© Sébastien Britton.



Sébastien Britton

CNRS Research associate

Nadia Barboule

CNRS Research associate

Patrick Calsou

INSERM Research director

Philippe Frit

CNRS Research associate

Dennis Gomez

CNRS Research associate

Florence Larminat

CNRS Research associate

Léa Marie

Fondation de France Fellow

Marie-Jeanne Pillaire

INSERM Research associate

Research Assistants

Florian David

Research Assistant - Roche ROADS program

Antonio Peixoto

CNRS Research Engineer

Nadège Preuilh

Research Assistant - Région Occitanie pre-maturation program

Carine Racca

CNRS Technician

Romane Trombetta

Research Assistant - Agence Nationale de la Recherche

PhD Students

Madeleine Bossaert

Fellow of the French Ministry of Higher Education and Research

Margaux Bossuat

Fellow of the UFTMIP/Occitanie Region

Jeanne Chauvat

Fellow of the Agence Nationale de la Recherche

Maryam Salim

Fellow of the UFTMIP/Occitanie Region

(Members of the DDR group in bold characters ; publications>2009 ; # co-first authors, * corresponding authors)


  • Demange P#, Joly E#, Marcoux J#, Zanon PRA, Listunov D, Rullière P, Barthes C, Noirot C, Izquierdo JB, Rozié A, Pradines K, Hee R, de Brito MV, Marcellin M, Serre RF, Bouchez O, Burlet-Schiltz O, Oliveira MCF, Ballereau S, Bernardes-Génisson V, Maraval V, Calsou P, Hacker SM, Génisson Y*, Chauvin R*, Britton S*. (2022) SDR enzymes oxidize specific lipidic alkynylcarbinols into cytotoxic protein-reactive species. eLife. doi: 10.7554/eLife.73913. 11:e73913. (Pubmed) (CNRS press release)


  • Racca C, Britton S, Hedouin S, Francastel C, Calsou P, Larminat F*. (2021). BRCA1 prevents R-loop-associated centromeric instability. Cell Death & Disease. doi: 10.1038/s41419-021-04189-3 (Pubmed(CNRS press release)
  • Zell J, Duskova K, Chouh L, Bossaert M, Cheron N, Granzhan A, Britton S*, Monchaud D*. (2021) Dual targeting of higher-order DNA structures by azacryptands induces DNA junction-mediated DNA damage in cancer cells. Nucleic Acids Research. doi: (Pubmed).
  • Sharma AB, Erasimus H, Pinto L, Caron M-C, Gopaul D, Peterlini T, Neumann K, Nazarov PV, Fritah S, Klink B, Herold-Mende CC, Niclou SP, Pasero P, Calsou P, Masson JY, Britton S, van Dick E*. (2021) XAB2 promotes Ku eviction from single-ended DNA double-strand breaks independently of the ATM kinase. Nucleic Acids Research. doi: 10.1093/nar/gkab785. (Pubmed).
  • Pipier A, Devaux A, Lavergne T, Adrait A, Couté Y, Britton S, Calsou P, Riou JF, Defrancq E, Gomez D. (2021) Constrained G4 structures unveil topology specificity of known and new G4 binding proteins. Scientific reports. doi: 10.1038/s41598-021-92806-8. 11(1):13469. (Pubmed).
  • Bossaert M#, Pipier A#, Riou JF, Noirot C, Nguyên LT, Serre RF, Bouchez O, Defrancq E, Calsou P*, Britton S*, Gomez D*. (2021) Transcription-associated topoisomerase 2α (TOP2A) activity is a major effector of cytotoxicity induced by G-quadruplex ligands. eLife. doi: 10.7554/eLife.65184. 10:e65184. (Pubmed) (CNRS press release).


  • Britton S#*, Chanut P#, Delteil C, Barboule N, Frit P, Calsou P*. (2020) ATM antagonizes NHEJ proteins assembly and DNA-ends synapsis at single-ended DNA double strand breaks. Nucleic Acids Res. doi: 10.1093/nar/gkaa723. 48:9710-9723. (Pubmed) (CNRS press release).
  • Duskova K, Lejault P, Benchimol É, Guillot R, Britton S*, Granzhan A*, Monchaud D*. (2020) DNA Junction Ligands Trigger DNA Damage and Are Synthetic Lethal with DNA Repair Inhibitors in Cancer Cells. J Am Chem Soc. doi: 10.1021/jacs.9b11150. 142:424-435. (Pubmed)


  • Cristini A, Ricci G, Britton S, Salimbeni S, Huang SN, Marinello J, Calsou P, Pommier Y, Favre G, Capranico G, Gromak N, Sordet O. (2019) Dual Processing of R-Loops and Topoisomerase I Induces Transcription-Dependent DNA Double-Strand Breaks. Cell Rep. doi: 10.1016/j.celrep.2019.08.041. 28:3167-3181. (Pubmed)
  • David AP, Pipier A, Pascutti F, Binolfi A, Weiner AMJ, Challier E, Heckel S, Calsou P, Gomez D, Calcaterra NB, Armas P. (2019) CNBP controls transcription by unfolding DNA G-quadruplex structures. Nucleic Acids Res. doi: 10.1093/nar/gkz527. 47:7901-7913. (Pubmed)
  • Duskova K, Lamarche J, Amor S, Caron C, Queyriaux N, Gaschard M, Penouilh MJ, de Robillard G, Delmas D, Devillers CH, Granzhan A, Teulade-Fichou MP, Chavarot-Kerlidou M, Therrien B, Britton S, Monchaud D. (2019) Identification of Three-Way DNA Junction Ligands through Screening of Chemical Libraries and Validation by Complementary in Vitro Assays. J Med Chem. doi: 10.1021/acs.jmedchem.8b01978. 62:4456-4466. (Pubmed)
  • Frit P, Ropars V, Modesti M, Charbonnier JB, and Calsou P. 2019. Plugged into the Ku-DNA hub: The NHEJ network. Prog Biophys Mol Biol. doi:10.1016/j.pbiomolbio.2019.03.001  (Pubmed) (invited review)
  • Pipier A,  De Rache A, Modeste C, Amrane S, Mothes-Martin E, Stigliani JL, Calsou P, Mergny JL, Pratviel G, and Gomez D. 2019. G-Quadruplex binding optimization by gold(iii) insertion into the center of a porphyrin. Dalton Trans.
    doi: 10.1039/c8dt04703k (Pubmed)


  • Rozie A, Santos C, Fabing I, Calsou P, Britton S*, Y. Genisson, and S. Ballereau*. (2018). Alkyne-Tagged Analogue of Jaspine B: New Tool for Identifying Jaspine B Mode of Action. Chembiochem. DOI: 10.1002/cbic.201800496. (PubMed) Article selected for ChemBioChem cover.


  • Nemoz C#, Ropars V#, Frit P#, Gontier A, Drevet P, Yu J, Guerois R, Pitois A, Comte A, Delteil C, Barboule N, Legrand P, Baconnais S, Yin Y, Tadi S, Barbet-Massin E, Berger I, Le Cam E, Modesti M, Rothenberg E, Calsou P* and Charbonnier JB.* (2018) XLF and APLF bind to Ku80 on two remote sites to ensure DNA repair by non-homologous end-joining. Nat. Struct. Mol. Biol. 25:971-980 (PubMed) (CEA press release) (CNRS press release). F1000PRIME recommended.


  • Bombarde O, Larminat F, Gomez D, Frit P, Racca P, Gomes B, Guilbaud N, Calsou P. (2017). The DNA binding polyamine moiety in the vectorized DNA topoisomerase II inhibitor F14512 alters reparability of the consequent enzyme-linked DNA double strand breaks, Mol Cancer Ther, 16:2166-77 (PubMed)


  • Chanut P, Britton S , Coates J, Jackson SP and Calsou P (2016) Coordinated nuclease activities release Ku from single-ended DNA double strand breaks. Nat Commun 7:12889 (PubMed) (CNRS news release)
  • Hegde M, Dutta A, Yang C, Mantha A, Hegde P, Pandey A, Sengupta S, Yu Y, P Calsou, Chen DJ, Lees-Miller S and S Mitra (2016) Scaffold Attachment Factor A (SAF-A) and Ku Temporally Regulate Repair of Radiation-induced Clustered Genome Lesions. Oncotarget 7:54430-54444 (PubMed)


  • Menchon G, Bombarde O, Trivedi M, Negrel A, Inard C, Giudetti B, Baltas M, Milon A, Modesti M, Czaplicki G and Calsou P (2016) Structure-Based Virtual Ligand Screening on the XRCC4/DNA Ligase IV Interface. Sci Rep 6:22878 (PubMed)
  • Lamaa A, Le Bras M, Skuli N, Britton S, Frit P, Calsou P, Prats H, Cammas A and Millevoi S (2016) A novel cytoprotective function for the DNA repair protein Ku in regulating p53 mRNA translation and function. EMBO Rep 17:508-518 (PubMed)
  • Chabalier-Taste C, Brichese L, Racca C, Canitrot Y, Calsou P and Larminat F (2016) Polo-like kinase 1 mediates BRCA1 phosphorylation and recruitment at DNA double-strand breaks. Oncotarget 19:2269-2283 (PubMed)


  • Yuan Y, Britton S, Delteil C, Coates J, Jackson SP, Barboule N, Frit P and Calsou P (2015) Single-stranded DNA oligomers stimulate error-prone alternative repair of DNA double-strand breaks through hijacking Ku protein. Nucleic Acids Res 43:10264-10276 (PubMed) (CNRS news release)
  • Douglas P, Ye R, Morrice N, Britton S, Trinkle-Mulcahy L and Lees-Miller SP. (2015) Phosphorylation of SAF-A/hnRNP-U Serine 59 by Polo-Like Kinase 1 Is Required for Mitosis. Mol Cell Biol 35:2699-2713 (PubMed)
  • Sabater L, Nicolau-Travers ML, De Rache A, Prado E, Dejeu J, Bombarde O, Lacroix J, Calsou P, Defrancq E, Mergny JL, Gomez D* and Pratviel G* (2015) The nickel(II) complex of guanidinium phenyl porphyrin, a specific G-quadruplex ligand, targets telomeres and leads to POT1 mislocalization in culture cells. J Biol Inorg Chem 20:729-738 (PubMed) (*corresponding authors)
  • Brown JS, Lukashchuk N, Sczaniecka-Clift M, Britton S, le Sage C, Calsou P, Beli P, Galanty Y and Jackson SP (2015) Neddylation Promotes Ubiquitylation and Release of Ku from DNA-Damage Sites. Cell Rep 11:704-714 (PubMed)


  • Di Paolo A, Racca CCalsou P and Larminat F (2014) Loss of BRCA1 impairs centromeric cohesion and triggers chromosomal instability. FASEB J 28:5250-5261 (PubMed)
  • Britton S#, Dernoncourt E#, Delteil C, Froment C, Schiltz O, Salles B, Frit P* and Calsou P* (2014). DNA damage triggers SAF-A and RNA biogenesis factors exclusion from chromatin coupled to R-loops removal. Nucleic Acids Res 42:9047-9062 (PubMed) (#equal contribution, *corresponding authors)
  • Frit PBarboule NYuan YGomez D and Calsou P (2014) Alternative End-Joining pathway(s): Bricolage at DNA breaks. DNA Repair 17:81-97 (PubMed)


  • Cottarel J, Frit PBombarde O, Salles B, Négrel A, Bernard S, Jeggo PA, Lieber MR, Modesti M andCalsou P (2013) A noncatalytic function of the ligation complex during nonhomologous end joining. J Cell Biol 200:173-186 (PubMed)
  • E Gicquel, JP Souchard, F Magnusson, J Chemaly, P Calsou and P Vicendo (2013) Role of intercalation and redox potential in DNA photosensitization by ruthenium(II) polypyridyl complexes: assessment using DNA repair protein tests. Photochem Photobiol Sci 12:1517-1526 (PubMed)


  • Cheng QBarboule NFrit PGomez DBombarde O, Couderc B, Ren G-S, Salles B and Calsou P(2011) Ku counteracts mobilization of PARP1 and MRN in chromatin damaged with DNA double-strand breaks. Nucleic Acids Res 39:9605-9619 (PubMed)
  • Romera C, Bombarde O, Bonnet R, Gomez D, Dumy P, Calsou P, Gwan JF, Lin JH, Defrancq E and Pratviel G (2011) Improvement of porphyrins for G-quadruplex DNA targeting. Biochimie 93:1310-1317 (PubMed)


  • Ye J, Lenain C, Bauwens S, Rizzo A, Saint-Léger A, Poulet A, Benarroch D, Magdinier F, Morere J, Amiard S, Verhoeyen E, Britton S, Calsou P, Salles B, Bizard A, Nadal M, Salvati E, Sabatier L, Wu Y, Biroccio A, Londoño-Vallejo A, Giraud-Panis MJ and Gilson E (2010) TRF2 and Apollo cooperate with Topoisomerase 2α to protect human telomeres from replicative damage. Cell 142:230-242 (PubMed)
  • Gomez D, Guédin A, Mergny J.L, Salles B, Riou J.F, Teulade-Fichou MP and Calsou P (2010) A G-quadruplex structure within the 5’-UTR of TRF2 mRNA represses translation in human cells. Nucleic Acids Res 38:7187-7198 (PubMed)
  • Bombarde O, Boby C, Gomez DFrit P, Giraud-Panis MJ, Gilson E, Salles B and Calsou P (2010) TRF2/RAP1 and DNA-PK mediate a double protection against joining at telomeric ends. EMBO J 29:1573-1584 (PubMed)


  • Britton S, Froment C, Frit P, Monsarrat B, Salles B and Calsou P (2009) Cell Nonhomologous End Joining capacity controls SAF-A phosphorylation by DNA-PK in response to DNA double-strand breaks inducers. Cell Cycle 8:3717-3722 (PubMed) (comment by K Meek in Cell Cycle 8:3809)
  • Britton SFrit P, Biard D, Salles B and Calsou P (2009) ARTEMIS nuclease facilitates apoptotic chromatin cleavage. Cancer Res 69:8120-8126 (PubMed)
  • Wu PY, Frit P*, Meesala S, Dauvillier S, Modesti M, Andres SN, Huang Y, Sekiguchi J, Calsou P, Salles B and Junop MS* (2009) Structural and functional interaction between the human DNA repair proteins DNA Ligase IV and XRCC4. Mol Cell Biol 29:3163-3172 (*corresponding authors) (PubMed)










  • 2022 ANR "inJUNCTION", collaboration between S.Britton, D. Monchaud, A. Granzhan, N. Chéron and L. Trantirek.
  • 2022 ANR "MAG4", to D.Gomez, collaboration with F. Benoit-Vical and V. Gervais.
  • 2022 INCA PLBIO collaboration between M.-J. Pillaire, S. Manenti and C. Joffre.
  • 2022 Roche ROADS program to A. Peixoto.
  • 2022 Cancéropôle Grand-Sud-Ouest – Soutien à l’Emergence. Projet "CRIM".
  • 2022 Ligue Régionale contre le Cancer to S. Britton, collaboration with Y. Génisson.
  • 2021 Prématuration Région Occitanie "Prostacure" to S. Britton, collaboration with Y. Génisson and R. Chauvin/V. Maraval.
  • 2021 ANR "iCARE", collaboration between D.Gomez, E. Defrancq, M. Delarue, A. Granzhan, J.-L. Mergny, J.-F. Riou.
  • 2020 ANR "BreakDance", collaboration between P. Calsou, J.-B. Charbonnier, M. Delarue, M. Modesti.
  • 2020 ANR "MELICENDRe", collaboration between F. Larminat, C. Francastel and D. Fachinetti.
  • 2019 Pre-Maturation grant from SATT-TTT to S. Britton, collaboration with Y. Génisson & R. Chauvin.
  • 2019 Plan Cancer Aviesan "DDRi" to S. Britton, collaboration with P. Dallemagne, CERMN, Caen.
  • 2019 Plan Cancer Aviesan "ANASTOMOSIS" to P.Calsou, collaboration with D. Monchaud, ICMUB, Dijon.
  • 2019 Cancéropôle Grand-Sud-Ouest – Soutien à l’Emergence. Projet "KILR".
  • 2019 Cancéropôle Grand-Sud-Ouest – Soutien à l’Emergence. Projet "CX-Break".
  • 2018-2020 Labellisation Ligue Nationale Contre le Cancer "Cassures double-brin de l'ADN : mécanismes de réparation et connexions thérapeutiques en oncologie".
  • 2018 Programme Prématuration Région Occitanie "OPTIBREAK", collaboration with Pascal demange, Lionel Mourey, Yves Génisson.
  • 2017 ANR "NHEJ LIG4", collaboration with M. Modesti and J.-B. Charbonnier"
  • 2017 Fondation ARC.  "Development of new anticancer agents". 
  • 2017 ANR JCJC to S. Britton. "Drugging DNA repair complexes". 
  • 2016 IDEX "Fishing out the intracellular target of novel antitumor pharmacophores bio-inspired from marine sponge" collaboration between S.Britton, Y. Génisson and R. Chauvin.
  •  2016 ANR "G4-TopIPro" collaboration between D. Gomez, E. Defrancq and J.-F. Riou.
  •  2016 Cancéropôle Grand Sud-Ouest – Soutien à l’Emergence (Cibles pharmacologiques de la Jaspine B) to S. Britton & P. Calsou.
  •  2016 Cancéropôle Grand Sud-Ouest – Soutien à l’Emergence (G4POPSTAR, collaboration with G. Pratviel and S. Millevoi).
  •  2016 Electricité de France - Conseil de Radioprotection.
  •  2015 Electricité de France - Conseil de Radioprotection.




We are always looking for motivated students and post-docs.


In addition to project specific grants that will be advertised on the website, several funding opportunities are available if you are willing to join the lab: Marie Skłodowska-Curie Fellowships (dead-line mid-October), EMBO Long-Term Fellowships (dead line in February), Fondation de France Fellowships (dead-line end of March), Fondation ARC Fellowships (dead-line in September) and FRM fellowships (dead-line in mid-April). If you have a good track record and fit well in the team, you can also apply with us to a Permanent Researcher position at CNRS (Chargé de Recherche) to join the team for the long run.


Each year, motivated students with a Master degree or equivalent can compete to obtain a PhD Fellowship from the Toulouse Doctoral School "Biologie-Santé-Biotechnologies".

Licence-Master internships

Research projects are usually advertised through each of the Masters (see here for the Master Biosanté). However, you can contact us in advance if you are interested by our research and want us to deposit a project in your favorite Master.

Summer internships

We frequently take summer students in the lab. The minimum duration for a summer internship in the lab is 1 month. Summer internships are good opportunities to learn basic to advanced laboratory techniques, gain experience, consolidate your CV, have your first publications and build up your network. See the French web-page to see which projects are available.