Models for FANCG-mediated interaction between monomers of FANCA. (A) A single molecule of FANCG mediates interaction between FANCA monomers. This interaction may involve physical bridging, with or without contact between the FANCA monomers. Models involving direct FANCA/FANCA contact could include the stabilization of a preexisting weak or transient interaction between FANCA monomers not detectable in the 2-hybrid system. Alternatively, FANCG may bind to only one FANCA monomer, causing structural change that allows for interaction with a second monomer. (B) Multiple molecules of FANCG are involved in the interaction. Simple examples of 2:2 FANCA/FANCG stoichiometry are illustrated. Such interactions could involve FANCA promoting or stabilizing FANCG/FANCG interactions not detectable in the 2-hybrid system. (C) FANCG modifies one or more molecules of FANCA, allowing for multimerization of FANCA without direct involvement of FANCG in the complex. Although this is possible, the strong direct interaction of FANCA and FANCG seen in the 2-hybrid system favors models involving FANCG complexed with FANCA.