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Cell Growth and Development

Ribosomal Protein L11 Negatively Regulates Oncoprotein MDM2 and Mediates a p53-Dependent Ribosomal-Stress Checkpoint Pathway

, , , , , & show all
Pages 8902-8912 | Received 27 Jun 2003, Accepted 21 Aug 2003, Published online: 27 Mar 2023
 

Abstract

The gene encoding p53 mediates a major tumor suppression pathway that is frequently altered in human cancers. p53 function is kept at a low level during normal cell growth and is activated in response to various cellular stresses. The MDM2 oncoprotein plays a key role in negatively regulating p53 activity by either direct repression of p53 transactivation activity in the nucleus or promotion of p53 degradation in the cytoplasm. DNA damage and oncogenic insults, the two best-characterized p53-dependent checkpoint pathways, both activate p53 through inhibition of MDM2. Here we report that the human homologue of MDM2, HDM2, binds to ribosomal protein L11. L11 binds a central region in HDM2 that is distinct from the ARF binding site. We show that the functional consequence of L11-HDM2 association, like that with ARF, results in the prevention of HDM2-mediated p53 ubiquitination and degradation, subsequently restoring p53-mediated transactivation, accumulating p21 protein levels, and inducing a p53-dependent cell cycle arrest by canceling the inhibitory function of HDM2. Interference with ribosomal biogenesis by a low concentration of actinomycin D is associated with an increased L11-HDM2 interaction and subsequent p53 stabilization. We suggest that L11 functions as a negative regulator of HDM2 and that there might exist in vivo an L11-HDM2-p53 pathway for monitoring ribosomal integrity.

ACKNOWLEDGMENTS

We thank John Cogswell and Cathy Finlay (GlaxoSmithKline) for providing the Hdm2 and p53 adenoviruses, Bert Vogelstein for providing pGL13-Luc plasmid, Karen Vousden for communicating their unpublished results, and Y. Joe He for helping figure preparation.

Y.Z. is a recipient of a Career Award in Biomedical Science from the Burroughs Wellcome Fund and a Howard Temin Award from National Cancer Institute. Y.X. is a recipient of a Career Development Award from the United States Department of Army Breast Cancer Research Program. This study was supported by the M. D. Anderson Research Trust (Y.Z.) and NIH grant CA65572 (Y.X.).

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