Description
To understand the principles underlying protein-protein interaction (PPI) complex changes in response to external perturbations, we created a highly multiplexed version of the murine dihydrofolate reductase protein complementation assay (mDHFR PCA) in Saccharomyces cerevisiae, allowing quantitative PPI complex profiling in vivo. We investigated the effects of 14 different conditions (including small molecules, abiotic stress factors, and nutrient composition) on a total of 1383 PPIs. More than half of PPIs (758) were found to be variable, and their Gene Ontology (GO) annotations were found to be informative of both the nature of the perturbation within each condition, as well as the overall variability of the interactions across conditions. Many perturbations triggered network changes characterized by large connected modules centered around highly connected proteins ('hubs'), suggesting that cellular control of a few proteins (e.g., by mRNA levels) can induce widespread PPI remodeling. Under a diauxic shift from glucose to ethanol as the main carbon source, we found a striking relationship between PPI changes measured by our assay and those predicted by mRNA expression under a simple law of mass action based model.