Fanconi anemia (FA) is characterized by hypersensitivity to DNA interstrand cross-linking agents. The resulting genomic instability is thought to underlie early-onset cancer, bone marrow failure, and other problems seen in the disease. Central to the FA DNA repair pathway is the Fanconi anemia I–Fanconi anemia D2 (ID) complex formed by the FANCD2 and FANCI proteins, which localize to sites of DNA repair. Joo et al. determined the crystal structure of the mouse ID complex and the isolated FANCI protein. The complex has a trough-like shape, with the monoubiquitination sites within the ID interface, at the bottom of the electropositive trough, in two solvent-accessible tunnels that could each accommodate a ubiquitin tail. The trough forms a series of grooves that, in FANCI, are able to bind to a Y-shaped fragment of DNA, suggesting how the complex might bind to a replication fork stalled at a DNA cross-link.
W. Joo, G. Xu, N. S. Persky, A. Smogorzewska, D. G. Rudge, O. Buzovetsky, S. J. Elledge, N. P. Pavletich, Structure of the FANCI-FANCD2 complex: Insights into the Fanconi anemia DNA repair pathway. Science 333, 312–316 (2011). [Abstract] [Full Text]