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Translational regulation of viral secretory proteins by 5’ coding regions and a viral RNA-binding protein
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.ORCID iD: 0000-0002-5864-8489
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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(English)In: Journal of Cell Biology, ISSN 0021-9525, E-ISSN 1540-8140Article in journal (Refereed) Accepted
Abstract [en]

A primary function of 5’ regions in many secretory protein mRNAs is to encode an endoplasmic reticulum (ER) targeting sequence. Here we show the regions coding for the ER-targeting sequences of the influenza proteins NA and HA also function as translational regulatory elements, which are controlled by the viral RNA-binding protein NS1. The translational increase depends on the nucleotide composition of the NA and HA ER-targeting sequences, their 5’ positioning, and is facilitated by the NS1 RNA-binding domain, which can associate with ER membranes. Inserting the ER-targeting sequence coding region of NA into different 5’UTRs confirmed that NS1 can promote the translation of secretory protein mRNAs based on the nucleotides within this region rather than the resulting amino acids. By analysing human protein mRNA sequences we found evidence that this mechanism of using 5’ coding regions and particular RNA-binding proteins to achieve gene-specific regulation may extend to human secreted proteins.

National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-141847OAI: oai:DiVA.org:su-141847DiVA: diva2:1089878
Available from: 2017-04-21 Created: 2017-04-21 Last updated: 2017-04-28
In thesis
1. NA transmembrane domain: Amphiphilic drift to accommodate two functions
Open this publication in new window or tab >>NA transmembrane domain: Amphiphilic drift to accommodate two functions
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Neuraminidase (NA) is one of two major antigens on the surface of influenza A viruses. It is comprised of a single N-terminal transmembrane domain (TMD), a stalk domain, and a C-terminal enzymatic head domain that cleaves sialic acid, most notably to release new particles from the host cell surface. NA is only enzymatically active as a homo-tetramer. However, it is not known which properties facilitate the oligomerization of NA during assembly. Our results show that, apart from anchoring the protein to the membrane, the NA TMD also contributes to the assembly process by keeping the stalk in a tetrameric conformation. The ability of the TMD to oligomerize is shown to be dependent on its amphiphilic characteristics that was largely conserved across the nine NA subtypes (N1-N9). Over time the NA TMDs in human H1N1 viruses were found to have become more amphiphilic, which correlated with stronger oligomerization. An old H1N1 virus with a more recent N1 TMD had impaired growth, but readily acquired compensatory mutations in the TMD to restore growth, by reverting the TMD oligomerization strength back to that of the old TMD, demonstrating a biological role of the TMD in folding and assembly. NA and the other viral proteins are spatially and temporally coordinated to achieve optimal viral production. By using a co-transfection analysis, the high AU-content in the NA and HA ER-targeting sequence coding regions (for NA TMD as well as the HA signal sequence) were found to inhibit their expression. The inhibition was alleviated by the early expressed influenza RNA-binding protein NS1, which promoted translation and showed enriched foci at the endoplasmic reticulum (ER). NS1, which expresses early during infection, is therefore likely the regulator of NA and HA to prevent premature expression. These results show that the NA TMD is under substantial selection pressure at both the nucleotide and amino acid level to accommodate its roles in ER-targeting, protein folding, and post-transcriptional regulation.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2017
Keyword
influenza, IAV, neuraminidase, NA, transmembrane domain, TMD, secretory protein, ER-targeting sequence, ER-targeting sequence coding region, protein regulation, NS1, GALLEX
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-142051 (URN)978-91-7649-825-5 (ISBN)978-91-7649-826-2 (ISBN)
Public defence
2017-06-05, Magnelisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
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Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Accepted.

Available from: 2017-05-11 Created: 2017-04-24 Last updated: 2017-05-12Bibliographically approved

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