Structural and biochemical basis of interdependent FANCI‐FANCD2 ubiquitination. (17th November 2022)

• Record Type: Journal Article
• Authors: Lemonidis, Kimon; Rennie, Martin L; Arkinson, Connor; Chaugule, Viduth K; Clarke, Mairi; Streetley, James; Walden, Helen
• Is Part Of: EMBO journal. Volume 42:Number 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-11-17
• Subjects: Fanconi anaemia -- interstrand crosslink repair -- deubiquitination -- USP1‐UAF1 -- DNA binding; Molecular biology -- Periodicals; 572.805
• DOI: 10.15252/embj.2022111898
• Languages: English
• ISSNs: 0261-4189

Abstract

Abstract: Di‐monoubiquitination of the FANCI‐FANCD2 (ID2) complex is a central and crucial step for the repair of DNA interstrand crosslinks via the Fanconi anaemia pathway. While FANCD2 ubiquitination precedes FANCI ubiquitination, FANCD2 is also deubiquitinated at a faster rate than FANCI, which can result in a FANCI‐ubiquitinated ID2 complex (IUb D2). Here, we present a 4.1 Å cryo‐EM structure of IUb D2 complex bound to double‐stranded DNA. We show that this complex, like ID2Ub and IUb D2Ub, is also in the closed ID2 conformation and clamps on DNA. The target lysine of FANCD2 (K561) becomes fully exposed in the IUb D2‐DNA structure and is thus primed for ubiquitination. Similarly, FANCI's target lysine (K523) is also primed for ubiquitination in the ID2Ub ‐DNA complex. The IUb D2‐DNA complex exhibits deubiquitination resistance, conferred by the presence of DNA and FANCD2. ID2Ub ‐DNA, on the other hand, can be efficiently deubiquitinated by USP1‐UAF1, unless further ubiquitination on FANCI occurs. Therefore, FANCI ubiquitination effectively maintains FANCD2 ubiquitination in two ways: it prevents excessive FANCD2 deubiquitination within an IUb D2Ub ‐DNA complex, and it enables re‐ubiquitination of FANCD2 within a transient, closed‐on‐DNA, IUb D2 complex. Synopsis: Monoubiquitination of each subunit of the DNA‐clamping FANCI‐FANCD2 (ID2) complex is a central step in DNA interstrand crosslink repair via the Fanconi Anemia pathway. Here, structural and biochemical studies elucidate the interdependence of these two ubiquitination events. Ubiquitination on any of the two subunits of the FANCI‐FANCD2 complex transforms the complex into a DNA clamp and promotes ubiquitination of the other subunit. When ubiquitinated FANCI associates with DNA, both FANCI and FANCD2 are protected against deubiquitination by USP1‐UAF1. Ubiquitin conjugated to FANCI forms extensive interactions with FANCD2, which further protect the FANCI‐ubiquitinated FANCI‐FANCD2‐DNA complex from deubiquitination. Abstract : A transient complex ubiquitinated only on FANCI, resulting from faster FANCD2 deubiquitination kinetics, remains clamped on DNA and favors FANCD2 re‐ubiquitination.