title: Ubiquitin-independent degradation of antiapoptotic MCL-1.
abstract: Antiapoptotic myeloid cell leukemia 1 (MCL-1) is an essential modulator of survival during the development and maintenance of a variety of cell lineages. Its turnover, believed to be mediated by the ubiquitin-proteasome system, facilitates apoptosis induction in response to cellular stress. To investigate the contribution of ubiquitinylation in regulating murine MCL-1 turnover, we generated an MCL-1 mutant lacking the lysine residues required for ubiquitinylation (MCL-1(KR)). Here, we demonstrate that despite failing to be ubiquitinylated, the MCL-1(KR) protein is eliminated at a rate similar to that of wild-type MCL-1 under basal and stressed conditions. Moreover, the degradation of wild-type MCL-1 is not affected when ubiquitin-activating enzyme E1 activity is blocked. Likewise, both wild-type and MCL-1(KR) proteins are similarly degraded when expressed in primary lymphocytes. Supporting these findings, unmodified, in vitro-translated MCL-1 can be degraded in a cell-free system by the 20S proteasome. Taken together, these data demonstrate that MCL-1 degradation can occur independently of ubiquitinylation.
authors.affiliation: Department of Biochemistry, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Stewart
authors.forename: Brian
authors.initials: B
authors.lastname: Koss
authors.forename: Madhavi
authors.initials: M
authors.lastname: Bathina
authors.forename: Rhonda M
authors.initials: RM
authors.lastname: Perciavalle
authors.forename: Kristen
authors.initials: K
authors.lastname: Bisanz
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Opferman
mesh_terms: D000483:Alleles; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006207:Half-Life; D006413:Hematopoietic System / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D061988:Proteasome Inhibitors; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D007976:Leupeptins; C579094:Mcl1 protein, mouse; D050505:Mutant Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D025801:Ubiquitin; D003513:Cycloheximide; D044767:Ubiquitin-Protein Ligases; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
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