scholarly journals Translation Initiation Factor eIF4B Interacts with a Picornavirus Internal Ribosome Entry Site in both 48S and 80S Initiation Complexes Independently of Initiator AUG Location

1999 ◽  
Vol 73 (9) ◽  
pp. 7505-7514 ◽  
Author(s):  
Kerstin Ochs ◽  
RenéC. Rust ◽  
Michael Niepmann
Keyword(s):  
Translation Initiation ◽  
Internal Ribosome Entry Site ◽  
Ribosomal Subunit ◽  
Translation Initiation Factor ◽  
Entry Site ◽  
Small Ribosomal Subunit ◽  
Internal Ribosome Entry ◽  
Initiation Factors ◽  
Mouth Disease Virus ◽  
Energy Dependent

ABSTRACT Most eukaryotic initiation factors (eIFs) are required for internal translation initiation at the internal ribosome entry site (IRES) of picornaviruses. eIF4B is incorporated into ribosomal 48S initiation complexes with the IRES RNA of foot-and-mouth disease virus (FMDV). In contrast to the weak interaction of eIF4B with capped cellular mRNAs and its release upon entry of the ribosomal 60S subunit, eIF4B remains tightly associated with the FMDV IRES during formation of complete 80S ribosomes. Binding of eIF4B to the IRES is energy dependent, and binding of the small ribosomal subunit to the IRES requires the previous energy-dependent association of initiation factors with the IRES. The interaction of eIF4B with the IRES in 48S and 80S complexes is independent of the location of the initiator AUG and thus independent of the mechanism by which the small ribosomal subunit is placed at the actual start codon, either by direct internal ribosomal entry or by scanning. eIF4B does not greatly rearrange its binding to the IRES upon entry of the ribosomal subunits, and the interaction of eIF4B with the IRES is independent of the polypyrimidine tract-binding protein, which enhances FMDV translation.

scholarly journals Interaction of Translation Initiation Factor eIF4B with the Poliovirus Internal Ribosome Entry Site

2002 ◽  
Vol 76 (5) ◽  
pp. 2113-2122 ◽  
Author(s):  
Kerstin Ochs ◽  
Lanja Saleh ◽  
Gergis Bassili ◽  
Volker H. Sonntag ◽  
Amandus Zeller ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Internal Ribosome Entry Site ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Initiation Factors ◽  
Polypyrimidine Tract Binding Protein ◽  
Energy Dependent ◽  
Domain V

ABSTRACT Poliovirus translation is initiated at the internal ribosome entry site (IRES). Most likely involving the action of standard initiation factors, this highly structured cis element in the 5" noncoding region of the viral RNA guides the ribosome to an internal silent AUG. The actual start codon for viral protein synthesis further downstream is then reached by ribosomal scanning. In this study we show that two of the secondary structure elements of the poliovirus IRES, domain V and, to a minor extent, domain VI, are the determinants for binding of the eukaryotic initiation factor eIF4B. Several mutations in domain V which are known to greatly affect poliovirus growth also seriously impair the binding of eIF4B. The interaction of eIF4B with the IRES is not dependent on the presence of the polypyrimidine tract-binding protein, which also binds to the poliovirus IRES. In contrast to its weak interaction with cellular mRNAs, eIF4B remains tightly associated with the poliovirus IRES during the formation of complete 80S ribosomes. Binding of eIF4B to the IRES is energy dependent, and binding of the small ribosomal subunit to the IRES requires the previous energy-dependent association of initiation factors with the IRES. These results indicate that the interaction of eIF4B with the 3" region of the poliovirus IRES may be directly involved in translation initiation.

scholarly journals Functional interaction of translation initiation factor eIF4G with the foot-and-mouth disease virus internal ribosome entry site

2001 ◽  
Vol 82 (4) ◽  
pp. 757-763 ◽  
Author(s):  
Lanja Saleh ◽  
René C. Rust ◽  
Ralf Füllkrug ◽  
Ewald Beck ◽  
Gergis Bassili ◽  
...  
Keyword(s):  
Translation Initiation ◽  
Foot And Mouth Disease ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Entry Site ◽  
Stem Loop ◽  
Internal Ribosome Entry ◽  
Initiation Factors ◽  
Mouth Disease Virus ◽  
Ires Element

In the life-cycle of picornaviruses, the synthesis of the viral polyprotein is initiated cap-independently at the internal ribosome entry site (IRES) far downstream from the 5′ end of the viral plus-strand RNA. The cis-acting IRES RNA elements serve as binding sites for translation initiation factors that guide the ribosomes to an internal site of the viral RNA. In this study, we show that the eukaryotic translation initiation factor eIF4G interacts directly with the IRES of foot-and-mouth disease virus (FMDV). eIF4G binds mainly to the large Y-shaped stem–loop 4 RNA structure in the 3′ region of the FMDV IRES element, whereas stem–loop 5 contributes only slightly to eIF4G binding. Two subdomains of stem–loop 4 are absolutely essential for eIF4G binding, whereas another subdomain contributes to a lesser extent to binding of eIF4G. At the functional level, the translational activity of stem–loop 4 subdomain mutants correlates with the efficiency of binding of eIF4G in the UV cross-link assay. This indicates that the interaction of eIF4G with the IRES is crucial for the initiation of FMDV translation. A model for the interaction of initiation factors with the IRES element is discussed.

The hepatitis C virus internal ribosome-entry site: a new target for antiviral research

2002 ◽  
Vol 30 (2) ◽  
pp. 140-145 ◽  
Author(s):  
J. Gallego ◽  
G. Varani
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Translation Initiation ◽  
Internal Ribosome Entry Site ◽  
Ribosomal Subunit ◽  
Initiation Factor ◽  
Entry Site ◽  
Viral Protein Synthesis ◽  
Initiation Mechanism ◽  
Internal Ribosome Entry

The hepatitis C virus (HCV) is the main causative agent of non-A, non-B hepatitis in humans and a major cause of mortality and morbidity in the world. Currently there is no effective treatment available for the infection caused by this virus, whose replication depends on an unusual translation-initiation mechanism. The viral RNA contains an internal ribosome-entry site (IRES) that is recognized specifically by the small ribosomal subunit and by eukaryotic initiation factor 3, and these interactions allow cap (7-methylguanine nucleotide)-independent initiation of viral protein synthesis. In this article, we review the structure and mechanism of translation initiation of the HCV IRES, and its potential as a target for novel antivirals.

scholarly journals Interaction of Eukaryotic Initiation Factor eIF4B with the Internal Ribosome Entry Site of Foot-and-Mouth Disease Virus Is Independent of the Polypyrimidine Tract-Binding Protein

1999 ◽  
Vol 73 (7) ◽  
pp. 6111-6113 ◽  
Author(s):  
René C. Rust ◽  
Kerstin Ochs ◽  
Karsten Meyer ◽  
Ewald Beck ◽  
Michael Niepmann
Keyword(s):  
Disease Virus ◽  
Translation Initiation ◽  
Internal Ribosome Entry Site ◽  
Foot And Mouth Disease ◽  
Initiation Factor ◽  
Polypyrimidine Tract ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Polypyrimidine Tract Binding Protein ◽  
Mouth Disease Virus

ABSTRACT Eukaryotic translation initiation factor 4B (eIF4B) binds directly to the internal ribosome entry site (IRES) of foot-and-mouth disease virus (FMDV). Mutations in all three subdomains of the IRES stem-loop 4 reduce binding of eIF4B and translation efficiency in parallel, indicating that eIF4B is functionally involved in FMDV translation initiation. In reticulocyte lysate devoid of polypyrimidine tract-binding protein (PTB), eIF4B still bound well to the wild-type IRES, even after removal of the major PTB-binding site. In conclusion, the interaction of eIF4B with the FMDV IRES is essential for IRES function but independent of PTB.

scholarly journals Conserved Nucleotides within the J Domain of the Encephalomyocarditis Virus Internal Ribosome Entry Site Are Required for Activity and for Interaction with eIF4G

2003 ◽  
Vol 77 (23) ◽  
pp. 12441-12449 ◽  
Author(s):  
Angela T. Clark ◽  
Morwenna E. M. Robertson ◽  
Graeme L. Conn ◽  
Graham J. Belsham
Keyword(s):  
Internal Ribosome Entry Site ◽  
Single Point ◽  
Encephalomyocarditis Virus ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Initiation Of Translation ◽  
Mouth Disease Virus ◽  
J Domain

ABSTRACT The internal ribosome entry site (IRES) elements of cardioviruses (e.g., encephalomyocarditis virus [EMCV] and foot-and-mouth disease virus) are predicted to have very similar secondary structures. Among these complex RNA structures there is only rather limited complete sequence conservation. Within the J domain of the EMCV IRES there are four highly conserved nucleotides (A704, C705, G723, and A724)., which are predicted to be unpaired and have been targeted for mutagenesis. Using an IRES-dependent cell selection system, we have isolated functional IRES elements from a pool of up to 256 mutants. All changes to these conserved nucleotides resulted in IRES elements that were less efficient at directing internal initiation of translation than the wild-type element, and even some of the single point mutants were highly defective. Each of the mutations adversely affected the ability of the RNAs to interact with the translation initiation factor eIF4G.

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

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.

scholarly journals Efficient Cleavage of Ribosome-Associated Poly(A)-Binding Protein by Enterovirus 3C Protease

2002 ◽  
Vol 76 (5) ◽  
pp. 2062-2074 ◽  
Author(s):  
N. Muge Kuyumcu-Martinez ◽  
Michelle Joachims ◽  
Richard E. Lloyd
Keyword(s):  
Translation Initiation ◽  
Binding Protein ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Initiation Factors ◽  
3C Protease

ABSTRACT Poliovirus (PV) causes a rapid and drastic inhibition of host cell cap-dependent protein synthesis during infection while preferentially allowing cap-independent translation of its own genomic RNA via an internal ribosome entry site element. Inhibition of cap-dependent translation is partly mediated by cleavage of an essential translation initiation factor, eIF4GI, during PV infection. In addition to cleavage of eIF4GI, cleavage of eIF4GII and poly(A)-binding protein (PABP) has been recently proposed to contribute to complete host translation shutoff; however, the relative importance of eIF4GII and PABP cleavage has not been determined. At times when cap-dependent translation is first blocked during infection, only 25 to 35% of the total cellular PABP is cleaved; therefore, we hypothesized that the pool of PABP associated with polysomes may be preferentially targeted by viral proteases. We have investigated what cleavage products of PABP are produced in vivo and the substrate determinants for cleavage of PABP by 2A protease (2Apro) or 3C protease (3Cpro). Our results show that PABP in ribosome-enriched fractions is preferentially cleaved in vitro and in vivo compared to PABP in other fractions. Furthermore, we have identified four N-terminal PABP cleavage products produced during PV infection and have shown that viral 3C protease generates three of the four cleavage products. Also, 3Cpro is more efficient in cleaving PABP in ribosome-enriched fractions than 2Apro in vitro. In addition, binding of PABP to poly(A) RNA stimulates 3Cpro-mediated cleavage and inhibits 2Apro-mediated cleavage. These results suggest that 3Cpro plays a major role in processing PABP during virus infection and that the interaction of PABP with translation initiation factors, ribosomes, or poly(A) RNA may promote its cleavage by viral 2A and 3C proteases.

Sign in / Sign up

Export Citation Format

Share Document