Ubiquitinylation is not an absolute requirement for degradation of c-Jun protein by the 26 S proteasome.
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.
Jariel-Encontre
I
I
Institut de Génétique Moléculaire/UMR 9942, Montpellier, France.
Pariat
M
M
Martin
F
F
Carillo
S
S
Salvat
C
C
Piechaczyk
M
M
D000818:Animals; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002467:Cell Nucleus / Q000201:enzymology; D002474:Cell-Free System; D003600:Cytosol / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D016755:Proto-Oncogene Proteins c-jun / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D014452:Ubiquitins / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D016755:Proto-Oncogene Proteins c-jun; D014452:Ubiquitins; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease