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. 2021 Apr;11(4):1076-1083.
doi: 10.1002/2211-5463.13106. Epub 2021 Feb 25.

Observation of arenavirus nucleoprotein heptamer assembly

Nicolas Papageorgiou  1 , Afroditi Vaitsopoulou  1   2 , Awa Diop  1 , Thi Hong Van Nguyen  1 , Bruno Canard  1   3 , Karine Alvarez  1 , François Ferron  1   3
Affiliations

Observation of arenavirus nucleoprotein heptamer assembly

Nicolas Papageorgiou et al. FEBS Open Bio. 2021 Apr.

Abstract

Arenaviruses are enveloped viruses containing a segmented, negative, and ambisense single-stranded RNA genome wrapped with a nucleoprotein (NP). The NP is the most abundant viral protein in infected cells and plays a critical role in both replication/transcription and virion assembly. The NP associates with RNA to form a ribonucleoprotein (RNP) complex, and this implies self-assembly while the exact structure of this polymer is not yet known. Here, we report a measurement of the full-length Mopeia virus NP by negative stain transmission electron microscopy. We observed RNP complex particles with diameter 15 ± 1 nm as well as symmetric circular heptamers of the same diameter, consistent with previous observations.

Keywords: Arenaviridae; Bunyavirales; assembly; nucleoprotein.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Fig. 1
Fig. 1
NP WebLogo representing the sequence conservation of Mammarenavirus sequences and their conservation on the structure (PDB: 3MWP). The WebLogo is derived from an alignment of 43 sequences (partial and identical sequences were previously removed). Domains and linker are indicated on the side of the alignment and the structure. Size of amino acid represents its conservation. On the structure, sequence identity is plotted by color change from deep blue (identical) to white (< 50%); missing linker is represented by a dashed line.
Fig. 2
Fig. 2
(A) MOPV‐NP size exclusion chromatography followed by UV at 280 nm (blue) and 260 nm (red). The three peaks fraction are delimited by two‐sided arrows and labeled M1, M2, M3. The M1 peak eluted as a multimer and has a 260/280 ratio over 1, indicating that the content is enriched in nucleic acid. (B) 12% SDS/PAGE analysis of M1, M2, M3 concentrated fractions, indicating that NP is mostly retrieved in M1. (C) General aspect of the sample studied shown in the bottom inset. The scale bar corresponds to a length of 100 nm.
Fig. 3
Fig. 3
(A) TEM images of RNP particles from freshly purified MOPV‐NP protein. The scale bar show a length of 30nm (B) class averages corresponding to heptamers observed in this experiment.
Fig. 4
Fig. 4
The upper part of the figure shows a 3D reconstruction of the observed heptameric particles at 27 Å resolution with the corresponding, FSC coefficient in function of the spatial frequencies in Å −1. At the bottom part of the figure are shown the particle classes used for the reconstruction.
Fig. 5
Fig. 5
Volume analysis of NP density and comparison with crystallographic data.
See this image and copyright information in PMC

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