Some components of regulatory networks can modify the impact of mutations to other components. For example, proteins that repress the activity of other proteins may also tend to buffer the impacts of mutations in the proteins they repress. What are the rules that dictate whether one protein buffers or enhances the impacts of mutations in another? To investigate rules that arise from regulatory relationships, my lab focuses on the network of proteins that are regulated by the protein-folding chaperone Hsp90. Hsp90 modifies the impacts of mutations in many genes, sometimes buffering these impacts but more often exaggerating them. My lab’s goal is to predict which mutations will be buffered v. enhanced by Hsp90. In doing so we strive to reveal generic rules that explain how regulatory network structure contributes to epistasis.