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Published May 1984 | metadata_only
Journal Article

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, shortlived 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.

Additional Information

© 1984 by MIT. Received 21 December 1983, Revised 2 March 1984. We are greatly indebted to Hideo Yasuda (University of California. Davis) for the gifts of ts85, FM3A, and ts85R-MN3 cells. This work was supported by grants to A. V. from the National Institute of General Medical Sciences (GM31530) and the National Cancer Institute (CA30367). A. C. was supported by the Melvin Brown Memorial Fellowship through the Israel Cancer Research Fund and by fellowships from the Leukemia Society of America and the Medical Foundation, Inc. D. F. was supported by a departmental training grant from the National Institutes of Health. A. C. wishes to express his profound gratitude to Harvey F. Lodish (MIT) for his support and encouragement during this work. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC. Section 1734 solely to indicate thus fact.

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August 19, 2023
August 19, 2023