scholarly journals A Rat Brain Bicistronic Gene with an Internal Ribosome Entry Site Codes for a Phencyclidine-binding Protein with Cytotoxic Activity

2008 ◽  
Vol 284 (4) ◽  
pp. 2245-2257 ◽  
Author(s):  
Dongwei Hui ◽  
Keshava N. Kumar ◽  
Julie R. Mach ◽  
Ashik Srinivasan ◽  
Ranu Pal ◽  
...  
Keyword(s):  
Cytotoxic Activity ◽  
Rat Brain ◽  
Internal Ribosome Entry Site ◽  
Binding Protein ◽  
Entry Site ◽  
Internal Ribosome Entry

scholarly journals Nuclear Protein Sam68 Interacts with the Enterovirus 71 Internal Ribosome Entry Site and Positively Regulates Viral Protein Translation

2015 ◽  
Vol 89 (19) ◽  
pp. 10031-10043 ◽  
Author(s):  
Hua Zhang ◽  
Lei Song ◽  
Haolong Cong ◽  
Po Tien
Keyword(s):  
Life Cycle ◽  
Internal Ribosome Entry Site ◽  
Viral Protein ◽  
Nuclear Protein ◽  
Binding Protein ◽  
Enterovirus 71 ◽  
Protein Translation ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Cellular Factors

ABSTRACTEnterovirus 71 (EV71) recruits various cellular factors to assist in the replication and translation of its genome. Identification of the host factors involved in the EV71 life cycle not only will enable a better understanding of the infection mechanism but also has the potential to be of use in the development of antiviral therapeutics. In this study, we demonstrated that the cellular factor 68-kDa Src-associated protein in mitosis (Sam68) acts as an internal ribosome entry site (IRES)trans-acting factor (ITAF) that binds specifically to the EV71 5′ untranslated region (5′UTR). Interaction sites in both the viral IRES (stem-loops IV and V) and the heterogeneous nuclear ribonucleoprotein K homology (KH) domain of Sam68 protein were further mapped using an electrophoretic mobility shift assay (EMSA) and biotin RNA pulldown assay. More importantly, dual-luciferase (firefly) reporter analysis suggested that overexpression of Sam68 positively regulated IRES-dependent translation of virus proteins. In contrast, both IRES activity and viral protein translation significantly decreased in Sam68 knockdown cells compared with the negative-control cells treated with short hairpin RNA (shRNA). However, downregulation of Sam68 did not have a significant inhibitory effect on the accumulation of the EV71 genome. Moreover, Sam68 was redistributed from the nucleus to the cytoplasm and interacts with cellular factors, such as poly(rC)-binding protein 2 (PCBP2) and poly(A)-binding protein (PABP), during EV71 infection. The cytoplasmic relocalization of Sam68 in EV71-infected cells may be involved in the enhancement of EV71 IRES-mediated translation. Since Sam68 is known to be a RNA-binding protein, these results provide direct evidence that Sam68 is a novel ITAF that interacts with EV71 IRES and positively regulates viral protein translation.IMPORTANCEThe nuclear protein Sam68 is found as an additional new host factor that interacts with the EV71 IRES during infection and could potentially enhance the translation of virus protein. To our knowledge, this is the first report that describes Sam68 actively participating in the life cycle of EV71 at a molecular level. These studies will not only improve our understanding of the replication of EV71 but also have the potential for aiding in developing a therapeutic strategy against EV71 infection.

scholarly journals Cleavage of Poly(A)-Binding Protein by Poliovirus 3C Proteinase Inhibits Viral Internal Ribosome Entry Site-Mediated Translation

2008 ◽  
Vol 82 (19) ◽  
pp. 9389-9399 ◽  
Author(s):  
Jennifer M. Bonderoff ◽  
Jennifer L. LaRey ◽  
Richard E. Lloyd
Keyword(s):  
Internal Ribosome Entry Site ◽  
Binding Protein ◽  
Virus Protein ◽  
Dependent Manner ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Initiation Factors ◽  
Polypyrimidine Tract Binding Protein ◽  
In Cells

ABSTRACT The two enteroviral proteinases, 2A proteinase (2Apro) and 3C proteinase (3Cpro), induce host cell translation shutoff in enterovirus-infected cells by cleaving canonical translation initiation factors. Cleavage of poly(A)-binding protein (PABP) by 3Cpro has been shown to be a necessary component for host translation shutoff. Here we show that 3Cpro inhibits cap-independent translation mediated by the poliovirus internal ribosome entry site (IRES) in a dose-dependent manner in HeLa translation extracts displaying cap-poly(A) synergy. This effect is independent of the stimulatory effect of 2Apro on IRES translation, and 3Cpro-induced translation inhibition can be partially rescued by addition of recombinant PABP in vitro. 3Cpro inhibits IRES translation on transcripts containing or lacking poly(A) tails, suggesting that cleavage of PABP and IRES trans-activating factors polypyrimidine tract-binding protein and poly r(C)-binding protein 2 may also be important for inhibition. Expression of 3Cpro cleavage-resistant PABP in cells increased translation of nonreplicating viral minigenome reporter RNAs during infection and also delayed and reduced virus protein synthesis from replicating RNA. Further, expression of cleavage-resistant PABP in cells reduced the accumulation of viral RNA and the output of infectious virus. These results suggest that cleavage of PABP contributes to viral translation shutoff that is required for the switch from translation to RNA replication.

A unique phosphorylation-dependent eIF4E assembly on 40S ribosomes co-ordinated by hepatitis C virus protein NS5A that activates internal ribosome entry site translation

2014 ◽  
Vol 462 (2) ◽  
pp. 291-302 ◽  
Author(s):  
Swarupa Panda ◽  
Dhiviya Vedagiri ◽  
Thangaraj Soundara Viveka ◽  
Krishnan Harinivas Harshan
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Internal Ribosome Entry Site ◽  
Binding Protein ◽  
Virus Protein ◽  
Entry Site ◽  
Complex Assembly ◽  
Internal Ribosome Entry ◽  
Cap Binding Complex

Hepatitis C virus (HCV) NS5A sequesters the phosphorylated mRNA cap-binding protein eIF4E from the cap-binding complex and assembles with 40S ribosome forming a tripartite complex. This complex assembly regulates HCV internal ribosome entry site-mediated translation.

scholarly journals Cytoplasmic Expression of mRNAs Containing the Internal Ribosome Entry Site and 3′ Noncoding Region of Hepatitis C Virus: Effects of the 3′ Leader on mRNA Translation and mRNA Stability

2002 ◽  
Vol 76 (24) ◽  
pp. 12457-12462 ◽  
Author(s):  
Li Kuo Kong ◽  
Peter Sarnow
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Translation Initiation ◽  
Internal Ribosome Entry Site ◽  
Binding Protein ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
Noncoding Regions ◽  
End Sequences ◽  
End To End

ABSTRACT Translation initiation in many eukaryotic mRNAs is modulated by an interaction between the cap binding protein complex, bound to the 5′ end of the mRNA, and the polyadenosine binding protein, bound to the 3′-terminal polyadenosine sequences. A few cellular and viral mRNAs, such as the hepatitis C virus (HCV) mRNA genome, lack 3′-terminal polyadenosine sequences. For such mRNAs, the question of whether their 3′-end sequences also regulate the initiation phase of protein synthesis via an interaction with their 5′ ends has received intense scrutiny. For HCV mRNA, various experimental designs have led to conflicting interpretations, that the 3′ end of the RNA can modulate translation initiation either in a positive or in a negative fashion. To examine the possibility of end-to-end communication in HCV in detail, mRNAs containing the HCV internal ribosome entry site linked to a luciferase coding region, followed by different 3′ noncoding regions, were expressed in the cytoplasm of cultured cells by T7 RNA polymerase. The intracellular translation efficiencies, steady-state levels, stabilities, and 3′-end sequences of these chimeric RNAs were examined. It was found that the HCV 3′ noncoding region modulates neither the translation nor the stability of the mRNAs. Thus, there is no detectable end-to-end communication in cytoplasmically expressed chimeric mRNAs containing the HCV noncoding regions. However, it remains an open question whether end-to-end communication occurs in full-length HCV mRNAs in the infected liver.

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