Interplay between ribosomal protein S27a and MDM2 protein in p53 activation in response to ribosomal stress

Xiao Xin Sun, Tiffany DeVine, Kishore B. Challagundla, Mu Shui Dai

57 Scopus citations


Ribosomal proteins play a critical role in tightly coordinating p53 signaling with ribosomal biogenesis. Several ribosomal proteins have been shown to induce and activate p53 via inhibition of MDM2. Here, we report that S27a, a small subunit ribosomal protein synthesized as an 80-amino acid ubiquitin C-terminal extension protein (CEP80), functions as a novel regulator of the MDM2-p53 loop. S27a interacts with MDM2 at the central acidic domain of MDM2 and suppresses MDM2-mediated p53 ubiquitination, leading to p53 activation and cell cycle arrest. Knockdown of S27a significantly attenuates the p53 activation in cells in response to treatment with ribosomal stress-inducing agent actinomycin D or 5-fluorouracil. Interestingly, MDM2 in turn ubiquitinates S27a and promotes proteasomal degradation of S27a in response to actinomycin D treatment, thus forming a mutual-regulatory loop. Altogether, our results reveal that S27a plays a non-redundant role in mediating p53 activation in response to ribosomal stress via interplaying with MDM2.

Original languageEnglish (US)
Pages (from-to)22730-22741
Number of pages12
JournalJournal of Biological Chemistry
Issue number26
Publication statusPublished - Jul 1 2011


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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