The ER membrane protein complex is required to ensure correct topology and stable expression of flavivirus polyproteins
Flaviviruses translate their genomes as multi-pass transmembrane proteins at the endoplasmic reticulum (ER) membrane. Here, we show that the ER membrane protein complex (EMC) is indispensable for the expression of viral polyproteins. We demonstrated that EMC was essential for accurate folding and post-translational stability rather than translation efficiency. Specifically, we revealed degradation of NS4A-NS4B, a region rich in transmembrane domains, in absence of EMC. Orthogonally, by serial passaging of virus on EMC-deficient cells, we identified two non-synonymous point mutations in NS4A and NS4B, which rescued viral replication. Finally, we showed a physical interaction between EMC and viral NS4B and that the NS4A-4B region adopts an aberrant topology in the absence of the EMC leading to degradation. Together, our data highlight how flaviviruses hijack the EMC for transmembrane protein biogenesis to achieve optimal expression of their polyproteins, which reinforces a role for the EMC in stabilizing challenging transmembrane proteins during synthesis.
Ribosome profiling/RNAseq data have been deposited as NCBI BioProject under the accession code PRJNA526529.
Article and author information
Howard Hughes Medical Institute
- Jonathan S Weissman
Helen Hay Whitney Foundation
- Matthew J Shurtleff
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Guangxia Gao, Institute of Biophysics, Chinese Academy of Sciences, China
- Received: May 15, 2019
- Accepted: September 13, 2019
- Accepted Manuscript published: September 13, 2019 (version 1)
- Version of Record published: September 23, 2019 (version 2)
© 2019, Ngo et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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