Monoubiquitination by the human Fanconi anemia core complex clamps FANCI:FANCD2 on DNA in filamentous arrays

• DOI: 10.7554/elife.54128
• Publication Date: 2020-03-13T13:00:19Z
• Authors: Winnie Tan; Sylvie van Twest; Andrew Leis; Rohan Bythell-Dou...; Vincent J Murphy; Michael Sharp; Michael W Parker; Wayne Crismani; Andrew J Deans
• Keywords: DNA Replication; 0303 health sciences; DNA Repair; QH301-705.5; Science; Fanconi Anemia Complementation Group D2 Protein; Q; R; Ubiquitination; 610; DNA repair; Chromosomes and Gene Expression; Fanconi Anemia Complementation Group Proteins; 3. Good health; 03 medical and health sciences; Fanconi anemia; ubiquitin; biochemistry; Medicine; Humans; Biology (General); DNA Damage

FANCI:FANCD2 monoubiquitination is a critical event for replication fork stabilization by the Fanconi anemia (FA) DNA repair pathway. It has been proposed that at stalled replication forks, monoubiquitinated-FANCD2 serves to recruit DNA repair proteins that contain ubiquitin-binding motifs. Here, we have reconstituted the FA pathway in vitro to study functional consequences of FANCI:FANCD2 monoubiquitination. We report that monoubiquitination does not promote any specific exogenous protein:protein interactions, but instead stabilizes FANCI:FANCD2 heterodimers on dsDNA. This clamping requires monoubiquitination of only the FANCD2 subunit. We further show using electron microscopy that purified monoubiquitinated FANCI:FANCD2 forms filament-like arrays on long dsDNA. Our results reveal how monoubiquitinated FANCI:FANCD2, defective in many cancer types and all cases of FA, is activated upon DNA binding.