INTRACELLULAR-DISTRIBUTION OF PROTEASOMES

Proteasomes are large multicatalytic proteinase complexes which are re sponsible for the selective degradation of cellular proteins and the p roduction of peptides for antigen presentation. Proteasomes are locali zed both in the nucleus and in the cytoplasm, where some are associate d with the endoplasmic reticulum membrane. Recent studies have shown d ifferences in the localization of proteasome subpopulations, demonstra ted the functional importance of endoplasmic reticulum-associated prot easomes and investigated the role of putative nuclear localization sig nals and tyrosine phosphorylation on proteasome transport into the nuc leus.