title: Susceptibility of p53 unstructured N terminus to 20 S proteasomal degradation programs the stress response.
abstract: The N-terminal transcription activation domain of p53 is intrinsically unstructured. We show in vitro and in vivo that this domain initiates p53 degradation by the 20 S proteasome in a ubiquitin-independent fashion. The decay of metabolically labeled p53 follows biphasic kinetics with an immediate fast phase that is ubiquitin-independent and a second slower phase that is ubiquitin-dependent. The 20 S proteasome executes the first phase by default, whereas the second phase requires the 26 S proteasome. p53 N-terminal binding proteins, such as Hdmx, can selectively block the first phase of degradation. Remarkably, gamma-irradiation inhibits both p53 decay phases, whereas UV selectively negates the second phase, giving rise to discrete levels of p53 accumulation. Our data of a single protein experiencing double mode degradation mechanisms each with unique kinetics provide the mechanistic basis for programmable protein homeostasis (proteostasis).
authors.affiliation: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Peter
authors.initials: P
authors.lastname: Tsvetkov
authors.forename: Nina
authors.initials: N
authors.lastname: Reuven
authors.forename: Carol
authors.initials: C
authors.lastname: Prives
authors.forename: Yosef
authors.initials: Y
authors.lastname: Shaul
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D005720:Gamma Rays; D045325:HCT116 Cells; D006602:Hexosyltransferases; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008956:Models, Chemical; D009154:Mutation; D041681:NIH 3T3 Cells; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D016159:Tumor Suppressor Protein p53; D006602:Hexosyltransferases; C517590:RPN2 protein, human; D046988:Proteasome Endopeptidase Complex