Degradation of rapidly turned over cellular proteins is commonly thought to be energy dependent, to require tagging of protein substrates by multi-ubiquitin chains, and to involve the 26 S proteasome, which is the major neutral proteolytic activity in both the cytosol and the nucleus. The c-Jun oncoprotein is very unstable in vivo. Using cell-free degradation assays, we show that ubiquitinylation, along with other types of tagging, is not an absolute prerequisite for ATP-dependent degradation of c-Jun by the 26 S proteasome. This indicates that a protein may bear intrinsic structural determinants allowing its selective recognition and breakdown by the 26 S proteasome. Moreover, taken together with observations by different groups, our data point to the notion of the existence of multiple degradation pathways operating on c-Jun.
Ubiquitinylation is not an absolute requirement for degradation of c-Jun protein by the 26 S proteasome
Jariel-Encontre, I.; Pariat, M.; Martin, F.; Carillo, S.; Salvat, C.; Piechaczyk, M.
J Biol Chem
1995-05-12 / vol 270 / pages 11623-7
Animals; Blotting, Western; Electrophoresis, Polyacrylamide Gel; Rats; Cell-Free System; Antibodies, Monoclonal; Molecular Weight; *Proteasome Endopeptidase Complex; Cell Nucleus/enzymology; Cytosol/enzymology; Liver/*enzymology; Peptide Hydrolases/isolation & purification/*metabolism; Proto-Oncogene Proteins c-jun/isolation & purification/*metabolism; Ubiquitins/*metabolism