title: The translation initiation factor DAP5 promotes IRES-driven translation of p53 mRNA.
abstract: Translational regulation of the p53 mRNA can determine the ratio between p53 and its N-terminal truncated isoforms and therefore has a significant role in determining p53-regulated signaling pathways. Although its importance in cell fate decisions has been demonstrated repeatedly, little is known about the regulatory mechanisms that determine this ratio. Two internal ribosome entry sites (IRESs) residing within the 5'UTR and the coding sequence of p53 mRNA drive the translation of full-length p53 and Δ40p53 isoform, respectively. Here, we report that DAP5, a translation initiation factor shown to positively regulate the translation of various IRES containing mRNAs, promotes IRES-driven translation of p53 mRNA. Upon DAP5 depletion, p53 and Δ40p53 protein levels were decreased, with a greater effect on the N-terminal truncated isoform. Functional analysis using bicistronic vectors driving the expression of a reporter gene from each of these two IRESs indicated that DAP5 preferentially promotes translation from the second IRES residing in the coding sequence. Furthermore, p53 mRNA expressed from a plasmid carrying this second IRES was selectively shifted to lighter polysomes upon DAP5 knockdown. Consequently, Δ40p53 protein levels and the subsequent transcriptional activation of the 14-3-3σ gene, a known target of Δ40p53, were strongly reduced. In addition, we show here that DAP5 interacts with p53 IRES elements in in vitro and in vivo binding studies, proving for the first time that DAP5 directly binds a target mRNA. Thus, through its ability to regulate IRES-dependent translation of the p53 mRNA, DAP5 may control the ratio between different p53 isoforms encoded by a single mRNA.
authors: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors: S
authors: S
authors: Weingarten-Gabbay
authors: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
authors: D
authors: D
authors: Khan
authors: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors: N
authors: N
authors: Liberman
authors: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors: Y
authors: Y
authors: Yoffe
authors: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors: S
authors: S
authors: Bialik
authors: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
authors: S
authors: S
authors: Das
authors: Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel.
authors: M
authors: M
authors: Oren
authors: Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
authors: A
authors: A
authors: Kimchi
mesh_terms: D048948:14-3-3 Proteins / Q000096:biosynthesis / Q000378:metabolism; D020121:5' Untranslated Regions / Q000235:genetics; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000378:metabolism; D045744:Cell Line, Tumor; D039603:Eukaryotic Initiation Factor-4G / Q000235:genetics / Q000378:metabolism*; D005095:Exoribonucleases / Q000096:biosynthesis / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D010442:Peptide Chain Initiation, Translational / Q000235:genetics*; D014176:Protein Biosynthesis; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics*; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis; D034741:RNA, Small Interfering; D012270:Ribosomes / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D048948:14-3-3 Proteins; D020121:5' Untranslated Regions; D014408:Biomarkers, Tumor; C491300:EIF4G2 protein, human; D039603:Eukaryotic Initiation Factor-4G; D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D005095:Exoribonucleases; C413442:SFN protein, human