The eIF4G homolog DAP5/p97 supports the translation of select mRNAs during endoplasmic reticulum stress

Lewis, Stephen M.; Cerquozzi, Sonia; Graber, Tyson E.; Ungureanu, Nicoleta Hosszu; Andrews, Meghan; Holčı́k, Martin

doi:10.1093/nar/gkm1007

Cited by 79 publications

(101 citation statements)

References 35 publications

(81 reference statements)

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“…The role of DAP5 in initiation of mRNA translation of IRES-containing genes in cellular stress conditions has been studied in different model systems. 14,15,19,27,28 However, proteolytic modifications of DAP5 by viral proteases and subsequent functional changes have not been previously explored. By site-directed mutagenesis, FMKSQ↓G 434 LSQ was identified as the cleavage site of 2A protease, consistent with cleavage recognition sites reported for other substrates of 2A.…”

Section: Discussionmentioning

confidence: 99%

“…FLAG-DAP5/97 plasmid (WT DAP5) was generously provided by Dr. Martin Holcik (Children's Hospital of Eastern Ontario, Ottawa, ON, Canada). 15 pIRES-2A was produced as described previously. 12 Cell lystates were prepared at 24 and/or 48 h after transfection for western blot analysis using the appropriate antibody, described below.…”

Section: Methodsmentioning

confidence: 99%

“…14 DAP5 initiates translation of proteins specifically expressed during development, cell cycle regulation and endoplasmic reticulum (ER) stress conditions, where global cap-dependent translation is compromised. 15,16 It has been reported that DAP5 regulates IRES-driven translation of Bcl-2 (B-cell lymphoma 2), p53, XIAP (X-linked inhibitor of apoptosis protein), CDK1 (cyclin-dependent kinase 1), c-Myc and other IRES-containing genes under conditions of stress, growth and apoptosis. [17][18][19] DAP5 mRNA also contains an IRES in its 5′-UTR, and is proficient in promoting its own translation, generating a positive feedback loop for its expression.…”

mentioning

confidence: 99%

“…[17][18][19] DAP5 mRNA also contains an IRES in its 5′-UTR, and is proficient in promoting its own translation, generating a positive feedback loop for its expression. 14,15 Additionally, DAP5 may undergo post-translational modifications, such as cleavage by caspases during apoptosis, generating a truncated, yet functional 86-kDa form of DAP5 that is more potent and efficient at translation initiation. 14 The role of DAP5 in initiation of IRES-driven translation has been studied in various model systems but not in the setting of viral infection.…”

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confidence: 99%

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Cleavage of DAP5 by coxsackievirus B3 2A protease facilitates viral replication and enhances apoptosis by altering translation of IRES-containing genes

Hanson

Qiu

et al. 2015

Cell Death Differ

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Cleavage of eukaryotic translation initiation factor 4G (eIF4G) by enterovirus proteases during infection leads to the shutoff of cellular cap-dependent translation, but does not affect the initiation of cap-independent translation of mRNAs containing an internal ribosome entry site (IRES). Death-associated protein 5 (DAP5), a structural homolog of eIF4G, is a translation initiation factor specific for IRES-containing mRNAs. Coxsackievirus B3 (CVB3) is a positive single-stranded RNA virus and a primary causal agent of human myocarditis. Its RNA genome harbors an IRES within the 5′-untranslated region and is translated by a cap-independent, IRES-driven mechanism. Previously, we have shown that DAP5 is cleaved during CVB3 infection. However, the protease responsible for cleavage, cleavage site and effects on the translation of target genes during CVB3 infection have not been investigated. In the present study, we demonstrated that viral protease 2A but not 3C is responsible for DAP5 cleavage, generating 45-and 52-kDa N-(DAP5-N) and C-terminal (DAP5-C) fragments, respectively. By site-directed mutagenesis, we found that DAP5 is cleaved at amino acid G434. Upon cleavage, DAP5-N largely translocated to the nucleus at the later time points of infection, whereas the DAP5-C largely remained in the cytoplasm. Overexpression of these DAP5 truncates demonstrated that DAP5-N retained the capability of initiating IRES-driven translation of apoptosis-associated p53, but not the prosurvival Bcl-2 (B-cell lymphoma 2) when compared with the full-length DAP5. Similarly, DAP5-N expression promoted CVB3 replication and progeny release; on the other hand, DAP5-C exerted a dominant-negative effect on cap-dependent translation. Taken together, viral protease 2A-mediated cleavage of DAP5 results in the production of two truncates that exert differential effects on protein translation of the IRES-containing genes, leading to enhanced host cell death. Coxsackievirus B3 (CVB3), a primary cause of viral myocarditis, is associated with sudden, unexpected death, 1 dilated cardiomyopathy and heart failure. 2 The CVB3 genome consists of a single open reading frame, which is translated to a polyprotein, and subsequently processed by viral proteases 2A and 3C. Similar to other picornaviruses, the CVB3 genome is linked to a small viral peptide, Vpg, rather than a 7-methyl guanosine cap structure at its 5′ terminus. Thus, CVB3 RNA is translated by a cap-independent mechanism and is driven by an internal ribosome entry site (IRES) harbored in the 5′ untranslated region (5′-UTR). 3,4 Viral proteases actively suppress multiple host cell activities that help the virus evade host defense mechanisms, promote viral replication and promote host cell apoptosis. For example, enterovirus proteases can cleave eukaryotic translation initiation factors 4GI (eIF4GI) 5-7 and eIF4GII. 8,9 Picornavirus proteases have also been reported to cleave other canonical translation initiation factors in the cap-dependent translation initiation complex, such as eIF5B 10 and ...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Cleavage of DAP5 by coxsackievirus B3 2A protease facilitates viral replication and enhances apoptosis by altering translation of IRES-containing genes

Hanson

Qiu

et al. 2015

Cell Death Differ

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“…Indeed, precedent for functional eIF4G isoforms exist in the literature. The eIF4G homologue protein DAP5/p97 is known to support translation of select mRNAs during endoplasmic reticulum stress and has also been proposed to function in non-stressed cells [14,15]. Although DAP5 lacks the eIF4E-binding domain, it could retain the capacity to interact with eIF4E homologues.…”

mentioning

confidence: 99%

Versatility of the translational machinery during stress: changing partners to keep dancing

Gebauer

2012

Cell Res

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Cap-dependent translation is initiated by the binding of eIF4E to the cap structure at the 5′ end of mRNAs. During hypoxic stress, global translation decreases because eIF4E is inactivated. In a recent article in Nature, Lee and colleagues show that residual hypoxic translation is maintained by a specialized isoform of eIF4E, which binds to target mRNAs in complex with a hypoxia-induced RNP.Translation of most messenger RNAs in the cell is initiated by binding of eukaryotic initiation factor (eIF) 4E to the m 7 GpppN cap structure at the mRNA 5′ end. Multiple eIF4E isoforms have been described in a variety of organisms along the evolutionary scale, but their functions remain for the most part obscure [1]. Translation is drastically reduced upon low oxygen tension (hypoxia) by mechanisms that inhibit the function of eIF4E. Cell function under hypoxia, however, is maintained by a significant degree of "residual" translation. In a recent article in Nature, Lee and colleagues show that the eIF4E homologue 4E2, in complex with the transcription factor HIF-2α and the RNA-binding protein RBM4, sustains cap-dependent translation during hy-. Thus, by using a specialized isoform of eIF4E in complex with a hypoxia-induced RNP, the translational machinery preserves selective protein synthesis during stress (Figure 1).The hypoxia inducible factor (HIF) family of transcription factors maintain cellular oxygen homeostasis. HIF-2α is induced under hypoxia and activates the expression of epidermal growth factor receptor (EGFR), a factor that confers growth advantage to hypoxic tumor cells. Lee and colleagues first show that the accumulation of EGFR is independent of the transcriptional activity of HIF-2α. First, EGFR protein accumulates in cells treated with transcription inhibitors; second, no changes in the steady state amounts of EGFR mRNA are detected upon hypoxia; and third, depletion of HIF-1β, a factor required for HIF transcriptional activity, has no effect on EGFR expression. These results pointed to a surprising direct role of HIF-2α in EGFR mRNA translation, a notion reinforced by the finding that HIF-2α associates with polysomes.The authors further show that HIF-2α associates to a region of EGFR 3′ UTR that is necessary and sufficient to drive translation of reporters in a HIF-2α-dependent manner. HIF-2α does not contain discernible RNA-binding motifs, raising the possibility that RNA binding is mediated by interactions with bridge RNA-binding proteins. An unbiased search for HIF-2α interactors identified RBM4, a protein involved in translational control [3,4]. RBM4 interacts with the HIF-2α-responsive region of EGFR 3′ UTR, and its depletion results in dissociation of HIF-2α from EGFR mRNA, indicating that RBM4 recruits HIF-2α to the 3′ UTR of the EGFR transcript. Furthermore, depletion of RBM4 abrogates the hypoxic translation of endogenous EGFR or EGFR reporters without affecting the levels of HIF-2α. Thus, RBM4 mediates the effects of HIF-2α in hypoxic translation of EGFR mRNA.But the HIF-2α/RBM4 complex regulate...

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Translation initiation by cap‐dependent ribosome recruitment: Recent insights and open questions

2018

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Gene expression universally relies on protein synthesis, where ribosomes recognize and decode the messenger RNA template by cycling through translation initiation, elongation, and termination phases. All aspects of translation have been studied for decades using the tools of biochemistry and molecular biology available at the time. Here, we focus on the mechanism of translation initiation in eukaryotes, which is remarkably more complex than prokaryotic initiation and is the target of multiple types of regulatory intervention. The "consensus" model, featuring cap-dependent ribosome entry and scanning of mRNA leader sequences, represents the predominantly utilized initiation pathway across eukaryotes, although several variations of the model and alternative initiation mechanisms are also known. Recent advances in structural biology techniques have enabled remarkable molecular-level insights into the functional states of eukaryotic ribosomes, including a range of ribosomal complexes with different combinations of translation initiation factors that are thought to represent bona fide intermediates of the initiation process. Similarly, high-throughput sequencing-based ribosome profiling or "footprinting" approaches have allowed much progress in understanding the elongation phase of translation, and variants of them are beginning to reveal the remaining mysteries of initiation, as well as aspects of translation termination and ribosomal recycling. A current view on the eukaryotic initiation mechanism is presented here with an emphasis on how recent structural and footprinting results underpin axioms of the consensus model. Along the way, we further outline some contested mechanistic issues and major open questions still to be addressed. This article is categorized under: Translation > Translation Mechanisms Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

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The eIF4G homolog DAP5/p97 supports the translation of select mRNAs during endoplasmic reticulum stress

Cited by 79 publications

References 35 publications

Cleavage of DAP5 by coxsackievirus B3 2A protease facilitates viral replication and enhances apoptosis by altering translation of IRES-containing genes

Cleavage of DAP5 by coxsackievirus B3 2A protease facilitates viral replication and enhances apoptosis by altering translation of IRES-containing genes

Versatility of the translational machinery during stress: changing partners to keep dancing

Translation initiation by cap‐dependent ribosome recruitment: Recent insights and open questions

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