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Updated: Jun 27, 2026

Purification of Ubiquitinated p53 Proteins from Mammalian Cells
Published on: March 21, 2022
Molecular basis of Pirh2-mediated p53 ubiquitylation
Yi Sheng1, Rob C Laister, Alexander Lemak
1Ontario Cancer Institute and Department of Medical Biophysics, University of Toronto, Ontario M5G1L7, Canada.
Abstract:
Pirh2 (p53-induced RING-H2 domain protein; also known as Rchy1) is an E3 ubiquitin ligase involved in a negative-feedback loop with p53. Using NMR spectroscopy, we show that Pirh2 is a unique cysteine-rich protein comprising three modular domains. The protein binds nine zinc ions using a variety of zinc coordination schemes, including a RING domain and a left-handed beta-spiral in which three zinc ions align three consecutive small beta-sheets in an interleaved fashion. We show that Pirh2-p53 interaction is dependent on the C-terminal zinc binding module of Pirh2, which binds to the tetramerization domain of p53. As a result, Pirh2 preferentially ubiquitylates the tetrameric form of p53 in vitro and in vivo, suggesting that Pirh2 regulates protein turnover of the transcriptionally active form of p53.
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