Bovine Adenovirus-3 pVIII Suppresses Cap-Dependent mRNA Translation Possibly by Interfering with the Recruitment of DDX3 and Translation Initiation Factors to the mRNA Cap.

Lisanework E Ayalew,Amit Gaba,Amrutlal K Patel,Azharul Islam,Suresh K Tikoo

doi:10.3389/fmicb.2016.02119

Lisanework E Ayalew, Amit Gaba + Show 3 more

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https://doi.org/10.3389/fmicb.2016.02119

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Journal: Frontiers in Microbiology	Publication Date: Dec 27, 2016
Citations: 5	License type: cc-by

Affiliation: University of Saskatchewan

Abstract

Earlier, targeting of DDX3 by few viral proteins has defined its role in mRNA transport and induction of interferon production. This study was conducted to investigate the function of bovine adenovirus (BAdV)-3 pVIII during virus infection. Here, we provided evidence regarding involvement of DDX3 in cap dependent cellular mRNA translation and demonstrated that targeting of DDX3 by adenovirus protein VIII interfered with cap-dependent mRNA translation function of DDX3 in virus infected cells. Adenovirus late protein pVIII interacted with DDX3 in transfected and BAdV-3 infected cells. pVIII inhibited capped mRNA translation in vitro and in vivo by limiting the amount of DDX3 and eIF3. Diminished amount of DDX3 and eIFs including eIF3, eIF4E, eIF4G, and PABP were present in cap binding complex in BAdV-3 infected or pVIII transfected cells with no trace of pVIII in cap binding complex. The total amount of eIFs appeared similar in uninfected or infected cells as BAdV-3 did not appear to degrade eIFs. The co-immunoprecipitation experiments indicated the absence of direct interaction between pVIII and eIF3, eIF4E, or PABP. These data indicate that interaction of pVIII with DDX3 interferes with the binding of eIF3, eIF4E and PABP to the 5′ Cap. We conclude that DDX3 promotes cap-dependent cellular mRNA translation and BAdV-3 pVIII inhibits translation of capped cellular mRNA possibly by interfering with the recruitment of eIFs to the capped cellular mRNA.

Highlights

DDX3, a member of DEAD (Asp-Glu-Ala-Asp) box family of RNA helicases (Tarn and Chang, 2009), is a 73 kDa nucleo-cytoplasmic shuttling protein and is biologically active both in the nucleus and the cytoplasm (Lai et al, 2008; Lee et al, 2008)
Proteomic analysis of the nucleoli of bovine adenovirus (BAdV)-3 infected and uninfected Madin-Darby Bovine Kidney (MDBK) cells identified a number of nucleolar proteins, which appeared to be involved in bovine adenovirus 3 (BAdV-3) infection (Patel and Tikoo, unpublished data)
Since one of these proteins identified as DDX3 appeared to be important for BAdV-3 replication, we initially determined if DDX3 interacted with any BAdV-3 protein using matchmaker GAL4 Yeast two hybrid assays (Supplementary file)

Summary

Introduction

DDX3, a member of DEAD (Asp-Glu-Ala-Asp) box family of RNA helicases (Tarn and Chang, 2009), is a 73 kDa nucleo-cytoplasmic shuttling protein and is biologically active both in the nucleus and the cytoplasm (Lai et al, 2008; Lee et al, 2008). DDX3 may accomplish modulation of cellular mRNA translation by interacting with specific eukaryotic translation initiation factors like eIF4E and PABP (Shih et al, 2012), eIF2α (Lai et al, 2008), eIF3 (Lee et al, 2008), or eIF4G (Soto-Rifo et al, 2012). There is a strong evidence for the active involvement of Ded, the yeast homologue of DDX3 in translation initiation (Chuang et al, 1997) and interacting with eIF4G (Hilliker et al, 2011). The translation of stalled mRNAs in vitro is repressed by Ded (Hilliker et al, 2011)

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