A review.A multi-million pound international program will put the Ubiquitin Proteasome System (UPS) center-stage for the identification of new drug targets.Profiling activities suggested that the UPS fell into an increasing 'sweet spot' for research and development.ITI LS's anal. showed that, while absolute numbers of publications about the UPS were lower than those of the better established targets, the rate of increase was much higher, pointing to a rapidly moving area of research.The UPS is the main route through which proteins are degraded within the nucleus and cytosol, and activity of this system has been implicated in processes as diverse as apoptosis, differentiation, proliferation, gene transcription, signal transduction and metabolic regulation.