The FA core complex contains a homo-dimeric catalytic module for the symmetric mono-ubiquitination of FANCI-FANCD2
journal contributionposted on 2020-10-15, 08:42 authored by Paolo Swuec, Ludovic Renault, Aaron Borg, Fenil Shah, Vincent J Murphy, Sylvie van Twest, Ambrosius P Snijders, Andrew J Deans, Alessandro Costa
Activation of the main DNA interstrand crosslink repair pathway in higher eukaryotes requires mono-ubiquitination of FANCI and FANCD2 by FANCL, the E3 ligase subunit of the Fanconi anemia core complex. FANCI and FANCD2 form a stable complex; however, the molecular basis of their ubiquitination is ill defined. FANCD2 mono-ubiquitination by FANCL is stimulated by the presence of the FANCB and FAAP100 core complex components, through an unknown mechanism. How FANCI mono-ubiquitination is achieved remains unclear. Here, we use structural electron microscopy, combined with crosslink-coupled mass spectrometry, to find that FANCB, FANCL, and FAAP100 form a dimer of trimers, containing two FANCL molecules that are ideally poised to target both FANCI and FANCD2 for mono-ubiquitination. The FANCC-FANCE-FANCF subunits bridge between FANCB-FANCL-FAAP100 and the FANCI-FANCD2 substrate. A transient interaction with FANCC-FANCE-FANCF alters the FANCI-FANCD2 configuration, stabilizing the dimerization interface. Our data provide a model to explain how equivalent mono-ubiquitination of FANCI and FANCD2 occurs.
DNA repairFanconi anemiacryo-electron microscopyinterstrand crosslinkmono-ubiquitinationubiquitin ligaseAmino Acid SequenceChromatography, High Pressure LiquidDNA-Binding ProteinsDimerizationFanconi Anemia Complementation Group D2 ProteinFanconi Anemia Complementation Group ProteinsHumansMass SpectrometryMicroscopy, ElectronProtein MultimerizationProtein Structure, TertiarySubstrate SpecificityUbiquitinationCosta FC001065PRT0601 Biochemistry and Cell Biology