Ubiquitin dependence of selective protein degradation demonstrated in the mammalian cell cycle mutant ts85.
We have shown that covalent conjugation of ubiquitin to proteins is temperature-sensitive in the mouse cell cycle mutant ts85 due to a specifically thermolabile ubiquitin-activating enzyme (accompanying paper). We show here that degradation of short-lived proteins is also temperature sensitive in ts85 , in contrast to wild-type and revertant cells. While more than 70% of the prelabeled abnormal proteins (containing amino acid analogs) or puromycyl peptides are degraded within 4 hr at the permissive temperature in both ts85 and wild-type cells, less than 15% are degraded in ts85 cells at the nonpermissive temperature. Degradation of abnormal proteins and puromycyl peptides in both ts85 cells and wild-type cells is nonlysosomal and ATP-dependent. Immunochemical analysis shows a strong and specific reduction in the levels of in vivo labeled ubiquitin-protein conjugates at the nonpermissive temperature in ts85 cells. Degradation of normal, short-lived proteins is also specifically temperature sensitive in ts85 . We suggest that the contribution of ubiquitin-independent pathways to the degradation of short-lived proteins in this higher eucaryotic cell is no more than 10%, and possibly less.
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D008325:Mammary Neoplasms, Experimental / Q000503:physiopathology; D051379:Mice; D009154:Mutation; D009363:Neoplasm Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009698:Nucleoproteins / Q000378:metabolism*; D013696:Temperature; D014452:Ubiquitins
D002868:Chromosomal Proteins, Non-Histone; D009363:Neoplasm Proteins; D009698:Nucleoproteins; D014452:Ubiquitins; D000255:Adenosine Triphosphate