Tumor Suppressor Protein Pdcd4 Inhibits Translation of p53 mRNA

Wedeken, Lena; Singh, Priyanka; Klempnauer, Karl‐Heinz

doi:10.1074/jbc.m111.269456

Cited by 67 publications

(79 citation statements)

References 45 publications

(38 reference statements)

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“…The specific role of PDCD4 in the unwinding of secondary structures via eIF4AI/II was further demonstrated by overexpression of mutant PDCD4, PDCD4-Mut4 (Fig. S1), which contains four amino acid substitutions in two MA3 domains and fails to interact with eIF4AI/II (29). These results showed that both NMD and overall translation levels of Rβ-SL9.7 mRNA were not affected by overexpression of mutant PDCD4 (Fig.…”

Section: Resultssupporting

confidence: 48%

eIF4AIII enhances translation of nuclear cap-binding complex–bound mRNAs by promoting disruption of secondary structures in 5′UTR

Choe

Ryu

Park

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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It has long been considered that intron-containing (spliced) mRNAs are translationally more active than intronless mRNAs (identical mRNA not produced by splicing). The splicing-dependent translational enhancement is mediated, in part, by the exon junction complex (EJC). Nonetheless, the molecular mechanism by which each EJC component contributes to the translational enhancement remains unclear. Here, we demonstrate the previously unappreciated role of eukaryotic translation initiation factor 4AIII (eIF4AIII), a component of EJC, in the translation of mRNAs bound by the nuclear cap-binding complex (CBC), a heterodimer of cap-binding protein 80 (CBP80) and CBP20. eIF4AIII is recruited to the 5′-end of mRNAs bound by the CBC by direct interaction with the CBCdependent translation initiation factor (CTIF); this recruitment of eIF4AIII is independent of the presence of introns (deposited EJCs after splicing). Polysome fractionation, tethering experiments, and in vitro reconstitution experiments using recombinant proteins show that eIF4AIII promotes efficient unwinding of secondary structures in 5′UTR, and consequently enhances CBC-dependent translation in vivo and in vitro. Therefore, our data provide evidence that eIF4AIII is a specific translation initiation factor for CBC-dependent translation.eIF4AIII | cap-binding complex | translation | CTIF | nonsense-mediated mRNA decay I n mammalian cells, translation initiation is driven by two major cap-binding proteins (CBPs). One is the nuclear cap-binding complex (CBC), which is a heterodimer of nuclear CBP80 and CBP20 (CBP80/20) (1), and the other is the eukaryotic translation initiation factor (eIF) 4E, which is a major cytoplasmic CBP (2). The CBC binds the 5′-cap structure of a newly synthesized mRNA in the nucleus and then directly interacts with an eIF4G-like scaffold protein called CBP80/20-dependent translation initiation factor (CTIF) (3). Because CTIF is mostly present on the cytoplasmic side of the nuclear envelope and is found in the nucleus (3), the interaction between the CBC and CTIF may occur either in the nucleus or during mRNA export through the nuclear pore complex. In the cytoplasm, at the 5′-end of mRNA, the CBC-CTIF complex recruits the eIF3 complex (4) and then the 40S small subunit of the ribosome, thereby directing the socalled "first" (or pioneer) round of translation (1).Translation of a CBC-bound mRNA precedes that of the eIF4E-bound mRNA, because the CBC-bound mRNA is a precursor form of the eIF4E-bound mRNA (5). The timing of the replacement of the CBC by eIF4E has not yet been elucidated; however, it is known that the replacement is mediated by the action of importin α/β in a translation-independent manner (6). The replaced eIF4E at the 5′-end of mRNA recruits a scaffold protein, eIF4GI or eIF4GII, which recruits eIF3 and eIF4AI/II and, eventually, the 40S ribosomal subunit. Then, the recruited 40S subunit scans the mRNA until it reaches the authentic translation initiation codon AUG. Efficient ribosome scanning requires either eIF4AI or e...

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Section: Resultssupporting

confidence: 48%

eIF4AIII enhances translation of nuclear cap-binding complex–bound mRNAs by promoting disruption of secondary structures in 5′UTR

Choe

Ryu

Park

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…For RNA isolation from mice livers, a part of the organ was Translational isoforms of p53 in glucose deprivation D Khan et al suspended in TRI reagent (Sigma-Aldrich) and 200-μg/ml glycogen, homogenized by handheld Down's homogenizer (Sigma-Aldrich) by 50 strokes on ice and then manufacturer's protocol was followed as usual. For real-time PCR, first-strand cDNA was synthesized using oligo-(dT) 18 primer (Thermo Scientific) using RevertAid RT enzyme (Thermo Scientific) from 2-μg RNA. Reaction was set up with 2 μl of 1 : 5 diluted cDNA using DyNAmo qPCR kit (Thermo Scientific) that uses SYBR Green chemistry as per manufacturer's instructions on ABI Prism 7900HT machine (Applied Biosystems, Life Technologies) or ABI ViiA7 machine (Applied Biosystems, Life Technologies).…”

Section: Methodsmentioning

confidence: 99%

Reversible induction of translational isoforms of p53 in glucose deprivation

et al. 2015

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Tumor suppressor protein p53 is a master transcription regulator, indispensable for controlling several cellular pathways. Earlier work in our laboratory led to the identification of dual internal ribosome entry site (IRES) structure of p53 mRNA that regulates translation of full-length p53 and Δ40p53. IRES-mediated translation of both isoforms is enhanced under different stress conditions that induce DNA damage, ionizing radiation and endoplasmic reticulum stress, oncogene-induced senescence and cancer. In this study, we addressed nutrient-mediated translational regulation of p53 mRNA using glucose depletion. In cell lines, this nutrient-depletion stress relatively induced p53 IRES activities from bicistronic reporter constructs with concomitant increase in levels of p53 isoforms. Surprisingly, we found scaffold/matrix attachment region-binding protein 1 (SMAR1), a predominantly nuclear protein is abundant in the cytoplasm under glucose deprivation. Importantly under these conditions polypyrimidine-tractbinding protein, an established p53 ITAF did not show nuclear-cytoplasmic relocalization highlighting the novelty of SMAR1-mediated control in stress. In vivo studies in mice revealed starvation-induced increase in SMAR1, p53 and Δ40p53 levels that was reversible on dietary replenishment. SMAR1 associated with p53 IRES sequences ex vivo, with an increase in interaction on glucose starvation. RNAi-mediated-transient SMAR1 knockdown decreased p53 IRES activities in normal conditions and under glucose deprivation, this being reflected in changes in mRNAs in the p53 and Δ40p53 target genes involved in cell-cycle arrest, metabolism and apoptosis such as p21, TIGAR and Bax. This study provides a new physiological insight into the regulation of this critical tumor suppressor in nutrient starvation, also suggesting important functions of the p53 isoforms in these conditions as evident from the downstream transcriptional target activation. Cell Death and Differentiation (2015) 22, 1203-1218; doi:10.1038/cdd.2014.220; published online 27 February 2015 p53 is a master transcription factor and tumor suppressor. Apart from post-translational modifications of p53 and concomitant protein-protein interactions of p53 with diverse factors, translational control of p53 mRNA also plays an important role under stress conditions. 1 p53 and its N-terminally truncated isoform Δ40p53 (also known as ΔN-p53 or p53/47) are translated by internal ribosome entry site (IRES)-mediated translation initiation from the same mRNA under different stress conditions that induce DNA damage, ionizing radiation and endoplasmic reticulum (ER) stress, oncogene-induced senescence and cancer. [2][3][4][5][6][7] Thus, p53 mRNA has a dual IRES structure. 8 For their function, these IRESs rely on IRES trans-acting factors (ITAFs). Polypyrimidine-tract-binding protein (PTB) was shown to have differential affinity for the two IRESs of p53 and regulated p53 IRES functions by translocating from nucleus to cytoplasm on doxorubicin-induced DNA damage. 3 This PTB-med...

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“…Fourth, PDCD4 is thought to suppress translation of mRNAs containing structured 5'-UTRs by interacting with translation initiation factor EIF4A and inhibiting its helicase activity via its ma3 domains. 38 Here, we have identified ATG5 mRNA but not ATG12 mRNA as a translational The cell viability was determined using ccK8 assay and Lc3 puncta level was detected by immunofluorescence with or without 3-MA treatment as described above. (G-I) skov3 cells were treated with pEGFP-C1 (Mock) or pEGFP-C1-PDCD4 (pPDcD4) plasmids; hepG2 cells were transfected with siRNA targeting PDCD4 (siP) or control (sic) respectively.…”

Section: Discussionmentioning

confidence: 99%