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p28, a first in class peptide inhibitor of cop1 binding to p53

T Yamada1, K Christov, A Shilkaitis

  • 1Department of Surgery, Division of Surgical Oncology, University of Illinois at Chicago College of Medicine, Chicago, IL, USA.

British Journal of Cancer
|June 6, 2013
PubMed
Abstract

Insights

The peptide p28, derived from azurin, increases levels of the tumor suppressor p53 in cancer cells by inhibiting its ubiquitination. This mechanism involves p28 binding to specific p53 DNA-binding domain motifs and inhibiting the COP1 ligase.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cancer Research

Background:

  • The cell-penetrating peptide p28, derived from Pseudomonas aeruginosa azurin, elevates p53 levels in cancer cells.
  • p28 functions by inhibiting p53 ubiquitination, a post-translational modification.
  • This mechanism is crucial for understanding p53 regulation in cancer therapy.

Purpose of the Study:

  • To identify specific binding sites of p28 within the p53 DNA-binding domain (DBD).
  • To elucidate the mechanism by which p28 increases p53 levels.
  • To investigate the role of E3 ligases in p28-mediated p53 stabilization.

Main Methods:

  • In silico simulations to predict p28 binding motifs on p53 DBD.
  • In vitro pull-down assays and western blotting to validate binding sites.
  • RT-PCR analysis to assess the expression of E3 ligases.

Main Results:

  • Specific p53 DBD motifs (L1 loop, S7-S8 loop, T140, P142, Q144, W146, R282, L289) were identified as p28 binding sites.
  • p28 significantly reduced COP1 (E3 ligase) levels (>80%) in p53 wild-type and mutant cells.
  • Expression of TOPORS, Pirh2, and HDM2 (human double minute 2) increased in response to p53 stabilization.

Conclusions:

  • p28 binds to specific motifs within the p53 DBD.
  • p28 inhibits cancer cell growth by increasing p53 levels through COP1 inhibition, independent of the HDM2 pathway.

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