Journal Article

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

Lees-Miller, Susan P., Wang, Annie, He, Yuan, Fishbain, Susan, Naila, Tasmin, Tomkinson, Alan E., Chen, Siyu, Lee, Linda

2021

Overview

DNA double-strand breaks (DSBs) are a highly cytotoxic form of DNA damage and the incorrect repair of DSBs is linked to carcinogenesis 1 , 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 receptors 2 , 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. Double-strand DNA break repair by the non-homologous end joining pathway involves the transition from a complex that bridges the DNA ends to a complex that aligns the DNA for ligation through the dissociation of the kinase subunits of the DNA-PK complexes.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 101/28 / 631/337/1427/2122 / 631/337/1427/2191 / 631/45/535/1258/1259 / 631/535/1258/1259 / 82/16 / 82/29 / 82/80 / 82/83 / Antibodies / Carcinogens / Cryoelectron Microscopy / Crystal structure / Cytotoxicity / Deoxyribonucleic acid / Dissociation / DNA / DNA - chemistry / DNA - metabolism / DNA - ultrastructure / DNA Breaks, Double-Stranded / DNA damage / DNA End-Joining Repair / DNA ligase (ATP) / DNA Ligase ATP - metabolism / DNA Ligase ATP - ultrastructure / DNA repair / DNA Repair Enzymes - metabolism / DNA Repair Enzymes - ultrastructure / DNA-Activated Protein Kinase - metabolism / DNA-Activated Protein Kinase - ultrastructure / DNA-Binding Proteins - metabolism / DNA-Binding Proteins - ultrastructure / DNA-dependent protein kinase / Electron microscopy / Genetic aspects / Genetic research / Homology / Humanities and Social Sciences / Humans / Kinases / Ku Autoantigen - metabolism / Ku Autoantigen - ultrastructure / Lymphocytes / Lymphocytes T / Models, Molecular / multidisciplinary / Non-homologous end joining / Phosphorylation / Protein kinase C / Protein kinases / Proteins / Scaffolds / Science / Science (multidisciplinary)