Internal Ribosome Entry Site-mediated Translation of a Mammalian mRNA Is Regulated by Amino Acid Availability

Fernandez, James; Yaman, Ibrahim; Mishra, Rangnath; Merrick, William C.; Snider, Martin D.; Lamers, Wouter H.; Hatzoglou, Maria

doi:10.1074/jbc.m009714200

Cited by 139 publications

(134 citation statements)

References 38 publications

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“…Autoradiograms were scanned and quantified using National Institutes of Health Image software. LUC activity in cell extracts was assayed as previously described (25). ATF4 was detected on Western blots using a polyclonal rabbit antibody from Santa Cruz Biotechnology.…”

Section: Methodsmentioning

confidence: 99%

Transcriptional Control of the Arginine/Lysine Transporter, Cat-1, by Physiological Stress

Fernandez¹,

Lopez²,

Wang³

et al. 2003

Journal of Biological Chemistry

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Cells respond to physiological stress by phosphorylating the ␣ subunit of the translation initiation factor eIF2. This adaptive response inhibits protein synthesis and up-regulates genes essential for cell survival. Cat-1, the transporter for the essential amino acids, arginine and lysine, is one of the up-regulated genes. We previously showed that stress increases cat-1 expression by coordinated stabilization of the mRNA and increased mRNA translation. This induction is triggered by amino acid depletion and the unfolded protein response (UPR), which is caused by unfolded proteins in the endoplasmic reticulum. We show here that cat-1 gene transcription is also increased by cellular stress. Our studies demonstrate that the cat-1 gene promoter/regulatory region is TATA-less and is located in a region that includes 94 bases of the first exon. Transcription from this promoter is stimulated 8-fold by cellular stress. An amino acid response element within the first exon is shown to be required for the response to amino acid depletion but not to the UPR. The stimulation of transcription by amino acid depletion requires activation of GCN2 kinase, which phosphorylates eIF2␣. This phosphorylation also induces translation of the cat-1 mRNA, demonstrating that stress-induced transcriptional and translational control of cat-1 are downstream targets of a signaling pathway initiating with eIF2␣ phosphorylation. Our studies show that the increase in cat-1 gene expression by cellular stress involves at least three types of coordinate regulation: regulation of transcription, regulation of mRNA stability, and regulation of mRNA translation.

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Section: Methodsmentioning

confidence: 99%

Transcriptional Control of the Arginine/Lysine Transporter, Cat-1, by Physiological Stress

Fernandez¹,

Lopez²,

Wang³

et al. 2003

Journal of Biological Chemistry

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“…However, the translation of the cationic amino-acid transporter gene cat-1 is stimulated under these conditions. It was found that an IRES whose activity is induced by amino-acid deprivation is responsible for the increased synthesis of cat-1 (Fernandez et al, 2001). Yaman and co-workers have proposed that the activity of this IRES is regulated by two sequential events.…”

Section: Regulation Of Gene Expression and Cellular Iressmentioning

confidence: 99%

Cellular internal ribosome entry segments: structures, trans-acting factors and regulation of gene expression

2004

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Initiation of translation in eukaryotic cells can occur by two distinct mechanisms, cap-dependent scanning and internal ribosome entry. The latter mechanism requires the formation of a complex RNA structural element termed an internal ribosome entry segment (IRES). IRESs are located in the 5 0 untranslated region of the message, and in the presence of trans-acting factors allow the ribosome to be recruited to a site that is a considerable distance from the cap structure. Many cellular mRNAs have now been shown to contain IRESs and it is likely that up to 10% of all mRNAs have the capability to initiate translation by this mechanism. The majority of IRESs that have been identified thus far are found in mRNAs whose protein products are associated with the control of cell growth and cell death, including many growth factors, proto-oncogenes and proteins required for apoptosis. In this review, we discuss the cellular situations when IRESs are required, the trans-acting factors that are necessary for IRES function and deregulation of IRES-mediated translation in tumorigenesis.

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“…21,22 Amino acid depletion induces GCN2 kinase-mediated phosphorylation of eIF2α, leading to a global decrease in protein synthesis and induction of an adaptive survival program. 21,23 Under this condition, IRES-mediated translation of the Cat-1 and SNAT2 mRNAs occur, 24,25 thus preparing cells to transport amino acids once they become available. Methionine synthase, a key enzyme that clears intracellular homocysteine, is induced by its cofactor, vitamin B12, at a translational level through an IRES in the 5'UTR of the mRNA.…”

mentioning

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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Internal Ribosome Entry Site-mediated Translation of a Mammalian mRNA Is Regulated by Amino Acid Availability

Cited by 139 publications

References 38 publications

Transcriptional Control of the Arginine/Lysine Transporter, Cat-1, by Physiological Stress

Transcriptional Control of the Arginine/Lysine Transporter, Cat-1, by Physiological Stress

Cellular internal ribosome entry segments: structures, trans-acting factors and regulation of gene expression

Reversible induction of translational isoforms of p53 in glucose deprivation

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