Structural basis of long-range to short-range synaptic transition in NHEJ

  • Nature. 2021 May;593(7858):294-298. doi: 10.1038/s41586-021-03458-7.
Siyu Chen  1  2 ,  Linda Lee  3  4 ,  Tasmin Naila  5  6  7 ,  Susan Fishbain  1 ,  Annie Wang  1 ,  Alan E Tomkinson  5  6  7 ,  Susan P Lees-Miller  3  4 ,  Yuan He  8  9  10  11
Affiliations
  • 1. Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA.
  • 2. Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, IL, USA.
  • 3. Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Alberta, Canada.
  • 4. Robson DNA Science Centre, Charbonneau Cancer Institute, University of Calgary, Calgary, Alberta, Canada.
  • 5. Department of Internal Medicine, University of New Mexico, Albuquerque, NM, USA.
  • 6. Department of Molecular Genetics & Microbiology, University of New Mexico, Albuquerque, NM, USA.
  • 7. University of New Mexico Comprehensive Cancer Center, University of New Mexico, Albuquerque, NM, USA.
  • 8. Department of Molecular Biosciences, Northwestern University, Evanston, IL, USA. [email protected].
  • 9. Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, IL, USA. [email protected].
  • 10. Chemistry of Life Processes Institute, Northwestern University, Evanston, IL, USA. [email protected].
  • 11. Robert H. Lurie Comprehensive Cancer Center of Northwestern University, Northwestern University, Chicago, IL, USA. [email protected].
PMID: 33854234 DOI: 10.1038/s41586-021-03458-7
Abstract

DNA double-strand breaks (DSBs) are a highly cytotoxic form of DNA damage and the incorrect repair of DSBs is linked to carcinogenesis1,2. The conserved error-prone non-homologous end joining (NHEJ) pathway has a key role in determining the effects of DSB-inducing agents that are used to treat Cancer as well as the generation of the diversity in antibodies and T cell receptors2,3. Here we applied single-particle cryo-electron microscopy to visualize two key DNA-protein complexes that are formed by human NHEJ factors. The Ku70/80 heterodimer (Ku), the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs), DNA Ligase IV (LigIV), XRCC4 and XLF form a long-range synaptic complex, in which the DNA ends are held approximately 115 Å apart. Two DNA end-bound subcomplexes comprising Ku and DNA-PKcs are linked by interactions between the DNA-PKcs subunits and a scaffold comprising LigIV, XRCC4, XLF, XRCC4 and LigIV. The relative orientation of the DNA-PKcs molecules suggests a mechanism for autophosphorylation in trans, which leads to the dissociation of DNA-PKcs and the transition into the short-range synaptic complex. Within this complex, the Ku-bound DNA ends are aligned for processing and ligation by the XLF-anchored scaffold, and a single catalytic domain of LigIV is stably associated with a nick between the two Ku molecules, which suggests that the joining of both strands of a DSB involves both LigIV molecules.