title: p28, a first in class peptide inhibitor of cop1 binding to p53.
abstract: BACKGROUND
  A 28 amino-acid (aa) cell-penetrating peptide (p28) derived from azurin, a redox protein secreted from the opportunistic pathogen Pseudomonas aeruginosa, produces a post-translational increase in p53 in cancer cells by inhibiting its ubiquitination.
  
  
  METHODS
  In silico computational simulations were used to predict motifs within the p53 DNA-binding domain (DBD) as potential sites for p28 binding. In vitro direct and competitive pull-down studies as well as western blot and RT-PCR analyses were used to validate predictions.
  
  
  RESULTS
  The L1 loop (aa 112-124), a region within the S7-S8 loop (aa 214-236) and T140, P142, Q144, W146, R282 and L289 of the p53DBD were identified as potential sites for p28 binding. p28 decreased the level of the E3 ligase COP1 >80%, in p53wt and p53mut cells with no decrease in COP1 in p53dom/neg or p53null cells. Brief increases in the expression of the E3 ligases, TOPORS, Pirh2 and HDM2 (human double minute 2) in p53wt and p53mut cells were in response to sustained increases in p53.
  
  
  CONCLUSIONS
  These data identify the specific motifs within the DBD of p53 that bind p28 and suggest that p28 inhibition of COP1 binding results in the sustained, post-translational increase in p53 levels and subsequent inhibition of cancer cell growth independent of an HDM2 pathway.
authors.affiliation: Department of Surgery, Division of Surgical Oncology, University of Illinois at Chicago College of Medicine, Chicago, IL, USA.
authors.forename: T
authors.initials: T
authors.lastname: Yamada
authors.forename: K
authors.initials: K
authors.lastname: Christov
authors.forename: A
authors.initials: A
authors.lastname: Shilkaitis
authors.forename: L
authors.initials: L
authors.lastname: Bratescu
authors.forename: A
authors.initials: A
authors.lastname: Green
authors.forename: S
authors.initials: S
authors.lastname: Santini
authors.forename: A R
authors.initials: AR
authors.lastname: Bizzarri
authors.forename: S
authors.initials: S
authors.lastname: Cannistraro
authors.forename: T K D
authors.initials: TK
authors.lastname: Gupta
authors.forename: C W
authors.initials: CW
authors.lastname: Beattie
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001400:Azurin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D054730:Protein Interaction Domains and Motifs / Q000187:drug effects / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D004791:Enzyme Inhibitors; D010446:Peptide Fragments; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D001400:Azurin; C471981:COP1 protein, human; D044767:Ubiquitin-Protein Ligases; C561466:azurin (50-77)