title: p53 directs conformational change and translation initiation blockade of human fibroblast growth factor 2 mRNA.
abstract: Tumour suppressor p53 has been shown to inhibit fibroblast growth factor 2 expression post-transcriptionally in cultured cells. Here we have investigated the mechanism responsible for this post-transcriptional blockade. Deletion mutagenesis of the FGF-2 mRNA leader revealed the requirement of at least four RNA cis-acting elements to mediate the inhibitory effect of p53 in SK-Hep-1 transfected cells, suggesting the involvement of RNA secondary or tertiary structures. Recombinant wild-type, but not Ala(143) mutant p53, was able to specifically repress FGF-2 mRNA translation in rabbit reticulocyte lysate, in a dose dependent manner. Sucrose gradient experiments showed that p53 blocks translation initiation by preventing 80S ribosome formation on an mRNA bearing the FGF-2 mRNA leader sequence. Interaction of wild-type and mutant p53 with different RNAs showed no significant correlation between p53 RNA binding activity and its translational inhibiting effect. However, by checking the accessibility of the FGF-2 mRNA leader to complementary oligonucleotide probes, we showed that the binding to RNA of wild-type, but not mutant p53, induced RNA conformational changes that might be responsible for the translational blockade. This strongly suggests that p53 represses FGF-2 mRNA translation by a direct mechanism involving its nucleic acid unwinding-annealing activity.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U397, Endocrinologie et Communication Cellulaire, Institut Fédératif de Recherche Louis Bugnard, C.H.U. Rangueil, 31403 Toulouse Cedex 04, France.
authors.forename: B
authors.initials: B
authors.lastname: Galy
authors.forename: L
authors.initials: L
authors.lastname: Créancier
authors.forename: L
authors.initials: L
authors.lastname: Prado-Lourenço
authors.forename: A C
authors.initials: AC
authors.lastname: Prats
authors.forename: H
authors.initials: H
authors.lastname: Prats
mesh_terms: D020121:5' Untranslated Regions; D000818:Animals; D019677:Artificial Gene Fusion; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000235:genetics; D016222:Fibroblast Growth Factor 2 / Q000096:biosynthesis / Q000235:genetics*; D006801:Humans; D009154:Mutation; D009690:Nucleic Acid Conformation; D010442:Peptide Chain Initiation, Translational; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D018411:Spodoptera / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology*
chemical_list: D020121:5' Untranslated Regions; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D016222:Fibroblast Growth Factor 2; D015500:Chloramphenicol O-Acetyltransferase