Cryo-EM of NHEJ supercomplexes provides insights into DNA repair

  • Mol Cell. 2021 Aug 19;81(16):3400-3409.e3. doi: 10.1016/j.molcel.2021.07.005.
Amanda K Chaplin  1 ,  Steven W Hardwick  2 ,  Antonia Kefala Stavridi  3 ,  Christopher J Buehl  4 ,  Noah J Goff  4 ,  Virginie Ropars  5 ,  Shikang Liang  3 ,  Taiana Maia De Oliveira  6 ,  Dimitri Y Chirgadze  2 ,  Katheryn Meek  4 ,  Jean-Baptiste Charbonnier  5 ,  Tom L Blundell  7
Affiliations
  • 1. Department of Biochemistry, University of Cambridge, Sanger Building, Tennis Court Road, Cambridge CB2 1GA, UK. Electronic address: [email protected].
  • 2. CryoEM Facility, Department of Biochemistry, University of Cambridge, Sanger Building, Tennis Court Road, Cambridge CB2 1GA, UK.
  • 3. Department of Biochemistry, University of Cambridge, Sanger Building, Tennis Court Road, Cambridge CB2 1GA, UK.
  • 4. College of Veterinary Medicine, Department of Microbiology & Molecular Genetics, Department of Pathobiology & Diagnostic Investigation, Michigan State University, East Lansing, MI 48824, USA.
  • 5. Institute for Integrative Biology of the Cell (I2BC), Institute Joliot, CEA, CNRS, Université Paris-Saclay, 91198, Gif-sur-Yvette Cedex, France.
  • 6. AstraZeneca R&D, Discovery Sciences, Mechanistic and Structural Biology, Cambridge, UK.
  • 7. Department of Biochemistry, University of Cambridge, Sanger Building, Tennis Court Road, Cambridge CB2 1GA, UK. Electronic address: [email protected].
PMID: 34352203 DOI: 10.1016/j.molcel.2021.07.005
Abstract

Non-homologous end joining (NHEJ) is one of two critical mechanisms utilized in humans to repair DNA double-strand breaks (DSBs). Unrepaired or incorrect repair of DSBs can lead to Apoptosis or Cancer. NHEJ involves several proteins, including the Ku70/80 heterodimer, DNA-dependent protein kinase catalytic subunit (DNA-PKcs), X-ray cross-complementing protein 4 (XRCC4), XRCC4-like factor (XLF), and Ligase IV. These core proteins bind DSBs and ligate the damaged DNA ends. However, details of the structural assembly of these proteins remain unclear. Here, we present cryo-EM structures of NHEJ supercomplexes that are composed of these core proteins and DNA, revealing the detailed structural architecture of this assembly. We describe monomeric and dimeric forms of this supercomplex and also propose the existence of alternate dimeric forms of long-range synaptic complexes. Finally, we show that mutational disruption of several structural features within these NHEJ complexes negatively affects DNA repair.

Keywords
DNA repair; DNA-PK; NHEJ; cryo-EM; long-range synaptic complexes; non-homologous end joining.