FANCI binds branched DNA and is monoubiquitinated by UBE2T-FANCL.

FANCI is integral to the Fanconi anemia (FA) pathway of DNA damage repair. Upon the occurrence of DNA damage, FANCI becomes monoubiquitinated on Lys-523 and relocalizes to chromatin, where it functions with monoubiquitinated FANCD2 to facilitate DNA repair. We show that FANCI and its C-terminal fragment possess a DNA binding activity that prefers branched structures. We also demonstrate that FANCI can be ubiquitinated on Lys-523 by the UBE2T-FANCL pair in vitro. These findings should facilitate future efforts directed at elucidating molecular aspects of the FA pathway.