The Fanconi Anemia (FA) pathway repairs DNA damage caused by endogenous and chemotherapy-induced DNA crosslinks, and responds to replication stress 1,2. Genetic inactivation of this pathway impairs development, prevents blood production and promotes cancer 1,3. The key molecular step in the FA pathway is the monoubiquitination of a pseudosymmetric heterodimer of FANCI-FANCD2 4,5 by the FA core complex-a megadalton multiprotein E3 ubiquitin ligase 6,7. Monoubiquitinated FANCD2 then recruits enzymes to remove the DNA crosslink or to stabilize the stalled replication fork. A molecular structure of the FA core complex would explain how it acts to maintain genome stability. Here we reconstituted an active, recombinant FA core complex, and used electron cryo-microscopy (cryoEM) and mass spectrometry to determine its structure. The FA core complex is comprised of two central dimers of the FANCB and FAAP100 subunits, flanked by two copies of the RING finger protein, FANCL. These two heterotrimers act as a scaffold to assemble the remaining five subunits, resulting in an extended asymmetric structure. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: