Eukaryotic cells, from yeast to human, contain some 6000 to 30000 protein-encoding genes and at least as many proteins. While much attention and research had been devoted to how proteins are synthesized, the reverse process, i.e. how proteins are degraded, long received little attention. The Nobel Prize in Chemistry for 2004 is shared between three scientists: Aaron Ciechanover, Avram Hershko and Irwin Rose who discovered ubiquitin-mediated proteolysis. Numerous cellular processes regulated by ubiquitin-mediated proteolysis include the immune response, cell cycle, DNA repair and transcription and protein quality control
