Cryo-EM structure of human DNA-PK holoenzymeYin, X., Liu, M., Tian, Y., Wang, J., Xu, Y.
(2017) Cell Res. 27: 1341-1350
- PubMed: 28840859
- DOI: 10.1038/cr.2017.110
- PubMed Abstract:
DNA-dependent protein kinase (DNA-PK) is a serine/threonine protein kinase complex composed of a catalytic subunit (DNA-PKcs) and KU70/80 heterodimer bound to DNA. DNA-PK holoenzyme plays a critical role in non-homologous end joining (NHEJ), the majo ...
DNA-dependent protein kinase (DNA-PK) is a serine/threonine protein kinase complex composed of a catalytic subunit (DNA-PKcs) and KU70/80 heterodimer bound to DNA. DNA-PK holoenzyme plays a critical role in non-homologous end joining (NHEJ), the major DNA repair pathway. Here, we determined cryo-electron microscopy structure of human DNA-PK holoenzyme at 6.6 Å resolution. In the complex structure, DNA-PKcs, KU70, KU80 and DNA duplex form a 650-kDa heterotetramer with 1:1:1:1 stoichiometry. The N-terminal α-solenoid (∼2 800 residues) of DNA-PKcs adopts a double-ring fold and connects the catalytic core domain of DNA-PKcs and KU70/80-DNA. DNA-PKcs and KU70/80 together form a DNA-binding tunnel, which cradles ∼30-bp DNA and prevents sliding inward of DNA-PKcs along with DNA duplex, suggesting a mechanism by which the broken DNA end is protected from unnecessary processing. Structural and biochemical analyses indicate that KU70/80 and DNA coordinately induce conformational changes of DNA-PKcs and allosterically stimulate its kinase activity. We propose a model for activation of DNA-PKcs in which allosteric signals are generated upon DNA-PK holoenzyme formation and transmitted to the kinase domain through N-terminal HEAT repeats and FAT domain of DNA-PKcs. Our studies suggest a mechanism for recognition and protection of broken DNA ends and provide a structural basis for understanding the activation of DNA-PKcs and DNA-PK-mediated NHEJ pathway.
Key Laboratory of Molecular Medicine, Ministry of Education, Department of Systems Biology for Medicine, School of Basic Medical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China.,Fudan University Shanghai Cancer Center, Institute of Biomedical Sciences, Shanghai Medical College of Fudan University, Shanghai 200032, China.,CAS Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai 200031, China.,State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, School of Life Sciences, Fudan University, Shanghai 200433, China.,State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China.