||The proteasome is a multicatalytic proteinase complex that is involved in the selective degradation of intracellular proteins. The 20S proteasome is the proteolytic core particle of a large protein degradation complex, the 26S proteasome. This 700 kDa protein is ubiquitously distributed in both the cytoplasm and the nucleus in all eukaryotes.The protein is responsible for degrading many cell-cycle control factors, signal transduction factors, transcription factors, and oncogene and anti-oncogene products, thus controlling cell proliferation, differentiation, and apoptosis. Changes in expression of the 20S proteasome have been documented in a number of physiological and pathological conditions such as skeletal muscle atrophy and Alzheimer neurodegeneration. Ethanol inhibits proteasome activity, resulting in the accumulation of insoluble protein aggregates known as Mallory bodies, a common signature of alcoholic liver diseases. On the other hand, proteosome inhibitors exhibit anti-inflammatory and antiproliferative effects, evidence that the proteosome may be an important drug target for the treatment for cancer and inflammatory diseases.