Effect of mutations downstream of the internal ribosome entry site on initiation of poliovirus protein synthesis.

While the majority of cellular mRNAs are translated by a cap-dependent mechanism, a subset of mRNAs can use an alternative mode of translation that, instead of cap, relies on discreet RNA elements that help to recruit the ribosome. This mode of translation, termed Internal Ribosome Entry Site (IRES)–dependent translation, is particularly important during conditions of compromised global protein synthesis or for a local, precisely timed translation of specific mRNAs. This latter purpose is of considerable importance in cells of the CNS for their normal function. Recently, the disruption of the IRES-mediated translation has also been linked to pathological processes, suggesting that full understanding and targeting of this peculiar mechanism could be used for therapeutic intervention.

Download Full-text

The hepatitis C virus internal ribosome entry site facilitates efficient protein synthesis in blood vessel endothelium during tumour angiogenesis

Nucleic Acids Research ◽

10.1093/nar/gng046 ◽

2003 ◽

Vol 31 (8) ◽

pp. 46e-46 ◽

Cited By ~ 3

Author(s):

G. T. Y. Chung

Keyword(s):

Protein Synthesis ◽

Hepatitis C Virus ◽

Hepatitis C ◽

Blood Vessel ◽

Internal Ribosome Entry Site ◽

Tumour Angiogenesis ◽

Entry Site ◽

Internal Ribosome Entry ◽

Virus Internal Ribosome Entry

Download Full-text

The internal ribosome entry site of the Dengue virus mRNA is active when cap-dependent translation initiation is inhibited.

Journal of Virology ◽

10.1128/jvi.01998-20 ◽

2020 ◽

Author(s):

Leandro Fernández-García ◽

Jenniffer Angulo ◽

Hade Ramos ◽

Aldo Barrera ◽

Karla Pino ◽

...

Keyword(s):

Protein Synthesis ◽

Dengue Virus ◽

Translation Initiation ◽

Internal Ribosome Entry Site ◽

Entry Site ◽

Internal Ribosome Entry ◽

Mouth Disease Virus ◽

Independent Mechanism ◽

In Cells

Dengue virus (DENV) is an enveloped, positive-sense, single-stranded RNA virus belonging to the Flaviviridae family. Translation initiation of the DENV mRNA can occur following a cap-dependent or a cap-independent mechanism. Two non-mutually exclusive cap-independent mechanisms of translation initiation have been described for the DENV mRNA. The first corresponds to a 5′end-dependent internal ribosome entry site (IRES)-independent mechanism, while the second relies on IRES-dependent initiation. In this report, we study the recently discovered DENV IRES. Results show that the DENV IRES is functional in the rabbit reticulocyte (RRL) in vitro translation system. In accordance, the activity of DENV IRES was resistant to the cleavage of eIF4G by the Foot-and-mouth disease virus leader protease in RRL. In cells, the DENV IRES exhibited only a marginal activity under standard culture conditions. The DENV IRES showed weak activity in HEK 293T cells; however, the DENV IRES activity was significantly enhanced in HEK 293T cells expressing the Human rhinovirus 2A protease. These findings suggest that the DENV IRES enables viral protein synthesis under conditions that suppress canonical translation initiation. IMPORTANCE Dengue virus (DENV), the etiological agent of Dengue, a febrile and hemorrhagic disease, infects millions of people per year in tropical and subtropical countries. When infecting cells, DENV induces stress conditions known to inhibit canonical protein synthesis. Under these conditions, DENV mRNA thrives using non-canonical modes of translation initiation. In this study, we characterize the mechanism dependent upon an internal ribosome entry site (IRES). Herein, we describe the activity of the DENV IRES in vitro and cells. We show that in cells, DENV IRES enables the viral mRNA to translate under conditions that suppress canonical translation initiation.

Download Full-text

Functional Insights into the Adjacent Stem-Loop in Honey Bee Dicistroviruses That Promotes Internal Ribosome Entry Site-Mediated Translation and Viral Infection

Journal of Virology ◽

10.1128/jvi.01725-17 ◽

2017 ◽

Vol 92 (2) ◽

Cited By ~ 4

Author(s):

Hilda H. T. Au ◽

Valentina M. Elspass ◽

Eric Jan

Keyword(s):

Protein Synthesis ◽

Virus Infection ◽

Honey Bee ◽

Internal Ribosome Entry Site ◽

Viral Protein ◽

Entry Site ◽

Viral Protein Synthesis ◽

Stem Loop ◽

Internal Ribosome Entry ◽

Paralysis Virus

ABSTRACTAll viruses must successfully harness the host translational apparatus and divert it toward viral protein synthesis. Dicistroviruses use an unusual internal ribosome entry site (IRES) mechanism whereby the IRES adopts a three-pseudoknot structure that accesses the ribosome tRNA binding sites to directly recruit the ribosome and initiate translation from a non-AUG start site. A subset of dicistroviruses, including the honey bee Israeli acute paralysis virus (IAPV), encode an extra stem-loop (stem-loop VI [SLVI]) 5′ adjacent to the intergenic region (IGR) IRES. Previously, the function of this additional stem-loop was unknown. Here, we provide mechanistic and functional insights into the role of SLVI in IGR IRES translation and in virus infection. Biochemical analyses of a series of mutant IRESs demonstrated that SLVI does not function in ribosome recruitment but is required for proper ribosome positioning on the IRES to direct translation. Using a chimeric infectious clone derived from the related cricket paralysis virus, we showed that the integrity of SLVI is important for optimal viral translation and viral yield. Based on structural models of ribosome-IGR IRES complexes, SLVI is predicted to be in the vicinity of the ribosome E site. We propose that SLVI of IAPV IGR IRES functionally mimics interactions of an E-site tRNA with the ribosome to direct positioning of the tRNA-like domain of the IRES in the A site.IMPORTANCEViral internal ribosome entry sites are RNA elements and structures that allow some positive-sense monopartite RNA viruses to hijack the host ribosome to start viral protein synthesis. We demonstrate that a unique stem-loop structure is essential for optimal viral protein synthesis and for virus infection. Biochemical evidence shows that this viral stem-loop RNA structure impacts a fundamental property of the ribosome to start protein synthesis.

Download Full-text