Dengue virus selectively annexes endoplasmic reticulum-associated translation machinery as a strategy for co-opting host cell protein synthesis


A primary question in Dengue virus (DENV) biology is the molecular strategy for recruitment of host cell protein synthesis machinery. Here we combined cell fractionation, ribosome profiling, and RNA-seq to investigate the subcellular organization of viral genome translation and replication as well as host cell translation and its response to DENV infection. We report that throughout the viral life cycle, DENV (+) and (-) strand RNAs were highly partitioned to the endoplasmic reticulum (ER), identifying the ER as the primary site of DENV translation. DENV infection was accompanied by an ER compartment-specific remodeling of translation, where ER translational capacity was subverted from host transcripts to DENV (+) strand RNA, particularly at late stages of infection. Remarkably, translation levels and patterns in the cytosol compartment were only modestly affected throughout the experimental time course of infection. Comparisons of ribosome footprinting densities of the DENV (+) strand RNA and host mRNAs indicated that DENV (+) strand RNA was only sparsely loaded with ribosomes. Combined, these observations suggest a mechanism where ER-localized translation and translational control mechanisms, likely cis-encoded, are used to repurpose the ER for DENV virion production. Consistent with this view, we found ER-linked cellular stress response pathways commonly associated with viral infection, namely the interferon response and unfolded protein response, to be only modestly activated during DENV infection. These data support a model where DENV reprograms the ER protein synthesis and processing environment to promote viral survival and replication, while minimizing the activation of anti-viral and proteostatic stress response pathways.ImportanceDENV, a prominent human health threat with no broadly effective or specific treatment, depends on host cell translation machinery for viral replication, immune evasion, and virion biogenesis. The molecular mechanism by which DENV commandeers the host cell protein synthesis machinery and the subcellular organization of DENV replication and viral protein synthesis is poorly understood. Here we report that DENV has an almost exclusively ER-localized life cycle, with viral replication and translation largely restricted to the ER. Surprisingly, DENV infection largely affects only ER-associated translation, with relatively modest effects on host cell translation in the cytosol. DENV RNA translation is very inefficient, likely representing a strategy to minimize disruption of ER proteostasis. Overall these findings demonstrate that DENV has evolved an ER-compartmentalized life cycle and thus targeting the molecular signatures and regulation of the DENV-ER interaction landscape may reveal strategies for therapeutic intervention.






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Publication Info

Reid, DW, RK Campos, JR Child, T Zheng, KWK Chan, SS Bradrick, SG Vasudevan, MA Garcia-Blanco, et al. (2018). Dengue virus selectively annexes endoplasmic reticulum-associated translation machinery as a strategy for co-opting host cell protein synthesis. Journal of Virology. 10.1128/JVI.01766-17 Retrieved from

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Christopher Vincent Nicchitta

Professor of Cell Biology

  Our laboratory studies the cellular architecture and regulation of protein synthesis, with the goal of understanding how cells regulate the subcellular organization and temporal dynamics of protein synthesis. We focus on mRNA localization - the process by which cells control where and when a protein is synthesized by localizing its mRNA to a discrete location(s) in the cell. Such regulation is critical for many aspects of cell dynamics, cell signaling and cell division. Of the diverse mRNA localization phenomena that have been identified to date, the most prominent is mRNA localization to the endoplasmic reticulum (ER). mRNA localization to the ER operates on an unusually large scale (essentially the entire mRNA transcriptome is partially represented on the ER, with those mRNAs encoding secretory and membrane proteins being highly ER-enriched), and continuously– all newly exported mRNAs undergo selection for translation in the cytosol and/or the ER compartments.

We use a broad array of experimental approaches - biochemistry, cell biology, genomics, and computational biology - and are focusing on several related themes. First, we are working to identify the mRNA-encoded signals used to target mRNAs to the ER as well as the cellular factors that recognize these signals. One mechanism, in which a signal in nascent secretory and membrane proteins directs mRNA recruitment to the ER, has been previously described. It is clear though that there are multiple pathways that direct mRNAs to the ER, including pathways that direct cytosolic and nucleoplasmic protein-encoding mRNAs to the ER. We are also investigating how, once localized, mRNAs are anchored to the ER membrane. In a recent study, we reported that the cohort of mRNAs encoding organelle resident proteins(e.g., nuclear envelope, ER, Golgi, lysosomes, peroxisomes) are localized tothe ER and directly anchored to components of the ER membrane. We are very interested in understanding the cis-encoded anchoring signals and the integral membrane proteins that function in mRNA anchoring to biological membrane, and lastly, how direct mRNA anchoring influences mRNA translation and mRNA stability.

In parallel efforts, we discovered that mRNA translation is under distinct regulatory control in the cytosol and ER compartments, with translation being 3-5 fold more efficient on the ER. These differences are substantial and suggest that mRNA localization to the ER may represent an important post-transcriptional gene expression mechanism. To gain insight into the mechanisms and factors responsible for the compartmental regulation of mRNA translation we are using traditional biochemical approaches (pulse-labeling, cell fractionation, immunoprecipitation, proteomics) as well as genomic approaches (ribosome footprinting, deep sequencing).

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