Promotion of Viral IRES-Mediated Translation Initiation under Mild Hypothermia.

Maria Licursi,Seyd Razavi,Ricardo A Carmona-Martinez,Kensuke Hirasawa,Eric Jan

doi:10.1371/journal.pone.0126174

Maria Licursi, Seyd Razavi + Show 3 more

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https://doi.org/10.1371/journal.pone.0126174

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Journal: PloS one	Publication Date: May 7, 2015
Citations: 3	License type: CC BY 4.0

Affiliation: Memorial University of Newfoundland

Abstract

Internal ribosome entry site (IRES)-mediated translation is an essential replication step for certain viruses. As IRES-mediated translation is regulated differently from cap-dependent translation under various cellular conditions, we sought to investigate whether temperature influences efficiency of viral IRES-mediated translation initiation by using bicistronic reporter constructs containing an IRES element of encephalomyocarditis virus (EMCV), foot-and-mouth disease virus (FMDV), hepatitis C virus (HCV), human rhinovirus (HRV) or poliovirus (PV). Under mild hypothermic conditions (30 and 35°C), we observed increases in the efficiency of translation initiation by HCV and HRV IRES elements compared to translation initiation at 37°C. The promotion of HRV IRES activity was observed as early as 2 hours after exposure to mild hypothermia. We also confirmed the promotion of translation initiation by HRV IRES under mild hypothermia in multiple cell lines. The expression levels and locations of polypyrimidine tract-binding protein (PTB) and upstream of N-Ras (unr), the IRES trans-acting factors (ITAFs) of HCV and HRV IRES elements, were not modulated by the temperature shift from 37°C to 30°C. Taken together, this study demonstrates that efficiency of translation initiation by some viral IRES elements is temperature dependent.

Highlights

Translation of eukaryotic mRNAs is comprised of four stages: initiation, elongation, termination and ribosome recycling
To determine whether culture temperature influences viral internal ribosome entry site (IRES)-mediated translation NIH3T3 cells were transfected with bicistronic IRES reporter constructs (encephalomyocarditis virus (EMCV), foot and mouth disease virus (FMDV), human rhinovirus (HRV), hepatitis C virus (HCV), poliovirus (PV) or the empty vector) (Fig 1A)
The absolute values of firefly luciferase activity were increased in cells transfected with HRV IRES reporter construct exposed to mild hypothermia for 4, 8 and 12 hours relative to cells cultured at 37°C (Fig 2A)

Summary

Introduction

Translation of eukaryotic mRNAs is comprised of four stages: initiation, elongation, termination and ribosome recycling. The majority of eukaryotic mRNA translation is initiated by a mechanism known as cap-dependent translation, termed as a cap structure at the terminal base of the 5’ untranslated region (5’ UTR) is required [4]. Translation of some viral and cellular mRNAs can be initiated by the direct binding of a ribosome to a unique RNA element called an internal ribosome entry site (IRES) [5–8]. IRES elements were first discovered in the mRNAs of the Picornaviridae [6,9]. Several other viral and cellular mRNAs have been reported to contain an IRES element [5,10–14]. The IRES contains a high degree of RNA secondary structure and PLOS ONE | DOI:10.1371/journal.pone.0126174. The IRES contains a high degree of RNA secondary structure and PLOS ONE | DOI:10.1371/journal.pone.0126174 May 7, 2015

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