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The translational response of the human mdm2 gene in HEK293T cells exposed to rapamycin: a role for the 5'-UTRs

Published inNucleic acids research, vol. 39, no. 3, p. 989-1003
Publication date2011
Abstract

Polysomal messenger RNA (mRNA) populations change rapidly in response to alterations in the physiological status of the cell. For this reason, translational regulation, mediated principally at the level of initiation, plays a key role in the maintenance of cellular homeostasis. In an earlier translational profiling study, we followed the impact of rapamycin on polysome re-seeding. Despite the overall negative effect on transcript recruitment, we nonetheless observed that some mRNAs were significantly less affected. Consequently, their relative polysomal occupancy increased in the rapamycin-treated cells. The behaviour of one of these genes, mdm2, has been further analysed. Despite the absence of internal ribosome entry site activity we demonstrate, using a dual reporter assay, that both the reported mdm2 5'-UTRs confer resistance to rapamycin relative to the 5'-UTR of β-actin. This relative resistance is responsive to the downstream targets mTORC1 but did not respond to changes in the La protein, a reported factor acting positively on MDM2 translational expression. Furthermore, extended exposure to rapamycin in the presence of serum increased the steady-state level of the endogenous MDM2 protein. However, this response was effectively reversed when serum levels were reduced. Taken globally, these studies suggest that experimental conditions can dramatically modulate the expressional output during rapamycin exposure.

Keywords
  • 5' Untranslated Regions
  • HEK293 Cells
  • Humans
  • Polyribosomes/drug effects
  • Protein Biosynthesis/drug effects
  • Protein Synthesis Inhibitors/pharmacology
  • Proto-Oncogene Proteins c-mdm2/genetics/metabolism
  • Sirolimus/pharmacology
Citation (ISO format)
GENOLET, Raphaël et al. The translational response of the human mdm2 gene in HEK293T cells exposed to rapamycin: a role for the 5′-UTRs. In: Nucleic acids research, 2011, vol. 39, n° 3, p. 989–1003. doi: 10.1093/nar/gkq805
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Article (Published version)
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ISSN of the journal0305-1048
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