Cryo-EM structures of NHEJ assemblies with nucleosomes.

Abstract:: DNA double-strand breaks (DSBs) are highly deleterious lesions that can trigger cell death or carcinogenesis if unrepaired or misrepaired. In mammals, most DSBs are repaired by non-homologous end joining (NHEJ), which begins when Ku70/80 binds DNA ends and recruits DNA-PKcs to form the DNA-PK holoenzyme. Although recent cryo-EM studies have resolved several NHEJ assemblies, how these factors access DSBs within nucleosomes remains unclear. Here, we present cryo-EM structures of human Ku70/80 and DNA-PK bound to nucleosomes. Ku70/80 binds the DNA end and bends it away from the nucleosome core, while the Ku70 C-terminal SAP domain makes an additional, specific DNA contact. Our DNA-PK-nucleosome structure further reveals the opening of the Ku80 vWA domain, and we show that non-hydrolysable ATP promotes synapsis by stabilising the Ku80-mediated DNA-PK dimer. These structures reveal a model for DSB recognition on nucleosomal DNA and provide insights relevant to targeting NHEJ in cancer therapy.

Authors:: C Hall, P Frit, A Kefala-Stavridi, A Pelletier, SW Hardwick, H Amin, MK Bilyard, T Maia De Oliviera, A Tariq, S Zahid, DY Chirgadze, S Balasubramanian, K Meek, V Ropars, J-B Charbonnier, M Modesti, P Calsou, S Britton, TL Blundell, T Schalch, AK Chaplin

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