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Molecular and Cellular Biology, October 2007, p. 7315-7333, Vol. 27, No. 20
0270-7306/07/$08.00+0     doi:10.1128/MCB.00272-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Regulation of H-ras Splice Variant Expression by Cross Talk between the p53 and Nonsense-Mediated mRNA Decay Pathways ^,

Jérôme Barbier, Martin Dutertre, Danielle Bittencourt, Gabriel Sanchez, Lise Gratadou, Pierre de la Grange, and Didier Auboeuf^*

INSERM U685, Equipe AVENIR, Hôpital Saint Louis, 1 Avenue Claude Vellefaux, Paris F-75010, France

Received 14 February 2007/ Returned for modification 6 March 2007/ Accepted 26 July 2007

When cells are exposed to a genotoxic stress, a DNA surveillance pathway that involves p53 is activated, allowing DNA repair. Eukaryotic cells have also evolved a mechanism called mRNA surveillance that controls the quality of mRNAs. Indeed, mutant mRNAs carrying premature translation termination codons (PTCs) are selectively degraded by the nonsense-mediated mRNA decay (NMD) pathway. However, in the case of particular genes, such as proto-oncogenes, mutations that do not create PTCs and therefore that do not induce mRNA degradation, can be harmful to cells. In this study, we showed that the H-ras gene in the absence of mutations produces an NMD-target splice variant that is degraded in the cytosol. We observed that a treatment with the genotoxic stress inducer camptothecin for 6 h favored the production of the H-ras NMD-target transcript degraded in the cytosol by the NMD process. Our data indicated that the NMD process allowed the elimination of transcripts produced in response to a short-term treatment with camptothecin from the major proto-oncogene H-ras, independently of PTCs induced by mutations. The camptothecin effects on H-ras gene expression were p53 dependent and involved in part modulation of the SC35 splicing factor. Interestingly, a long-term treatment with camptothecin as well as p53 overexpression for 24 h resulted in the accumulation of the H-ras NMD target in the cytosol, although the NMD process was not completely inhibited as other NMD targets are not stabilized. Finally, Upf1, a major NMD effector, was necessary for optimal p53 activation by camptothecin, which is consistent with recent data showing that NMD effectors are required for genome stability. In conclusion, we identified cross talk between the p53 and NMD pathways that regulates the expression levels of H-ras splice variants.

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* Corresponding author. Mailing address: INSERM U685, Institut Universitaire d'Hematologie, Hopital Saint-Louis, 1 Avenue Claude Vellefaux, Paris 75010, France. Phone: (33) 1 53 72 21 30. Fax: (33) 1 42 40 95 57. E-mail: auboeuf{at}stlouis.inserm.fr

Published ahead of print on 20 August 2007.

Supplemental material for this article may be found at http://mcb.asm.org/.

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Molecular and Cellular Biology, October 2007, p. 7315-7333, Vol. 27, No. 20
0270-7306/07/$08.00+0     doi:10.1128/MCB.00272-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

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