Biophysical characterization of the interaction between FAAP20-UBZ4 domain and Rev1-BRCT domain.

FAAP20 (Fanconi anemia-associated protein 20) is a subunit of the Fanconi anemia (FA) core complex that repairs interstrand cross-links. To understand the molecular basis for the FA core complex-mediated recruitment of Rev1 to the DNA lesion, we characterized the interactions among FAAP20-UBZ4, Rev1-BRCT, and ubiquitin using NMR. We found that FAAP20-UBZ4 binds not only ubiquitin but also Rev1-BRCT. Mapping the protein-protein interactions showed that FAAP20-UBZ4 has distinct binding surfaces for ubiquitin and Rev1-BRCT. In addition, the chemical exchange patterns indicated that the interaction between FAAP20-UBZ4 and ubiquitin might enhance the binding affinity between FAAP20-UBZ4 and Rev1-BRCT. These results provide new insight into the Rev1 recognition mechanism by FAAP20.