ROLE OF THE UBIQUITIN PROTEASOME SYSTEM IN REGULATED PROTEIN-DEGRADATION IN SACCHAROMYCES-CEREVISIAE/

Selective degradation of proteins in eukaryotes is mediated primarily by the ubiquitin system in conjunction with the 26S proteasome. The ye ast Saccharomyces cerevisiae has proved a powerful model system to stu dy protein degradation in vivo. Biochemical and genetic studies comple mented by the sequence analysis of the entire yeast genome have identi fied more than 70 genes presumed to function in the ubiquitin/proteaso me system. Moreover, a number of physiological substrates of the ubiqu itin system have been identified in yeast which are key regulatory pro teins involved in the control of the cell cycle and transcription. In this review we will describe the enzymes effecting ubiquitin-protein c onjugation and degradation. In addition we will discuss several target s of this system and describe the cellular functions mediated by this pathway.