Nucleocapsid-like cryo-EM structure of influenza B virus

Abstract

Influenza viruses belong to the Orthomyxoviridae family, they are categorized into four types: A, B, C, and D. Influenza B viruses co-circulate annually with influenza A strains during seasonal flu epidemics in humans, causing severe disease. The segmented RNA encapsidated by multiple copies of the nucleoprotein (NP) and attached to the heterotrimeric polymerase forms the central replicative unit called the viral ribonucleoprotein (vRNP). All influenza NP proteins share the same core domain folding, only NP of influenza B virus (B/NP) has an extended unfolded N-terminal tail of 70 amino-acids. This disordered N-terminal tail is required for nuclear localization of the protein, and may be involved in viral RNA transcription and replication regulation. In this study, we report that in absence of the extended N-terminal tail, the truncated NP maintains RNA binding ability and NP oligomeric state in vitro . We then reconstituted RNP-like particles by incubating truncated B/NP with synthetic RNA and we solved the cryo-EM structure at 4.1 Å resolution. Their morphology appears identical to native vRNPs extracted from viruses when observed by negative-stain electron microscopy. Overall, our results suggest that vRNPs from influenza virus type A, B and D share the same right-handed antiparallel helical conformation and that the B/NP N-terminal tail does not participate to the helical architecture stabilization once the vRNPs are assembled.

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Cite

BibTeX RIS

BibTeX

@article{thirion2026nucleocapsidlike,
  title = {{Nucleocapsid-like cryo-EM structure of influenza B virus}},
  author = {Marie Thirion and Alice Stelfox and Florian Chenavier and Héléna Chomat and Catherine Isel and Lily-Lorette Freslon and Eleftherios Zarkadas and Rob Ruigrok and Nadia Naffakh and Thibaut Crépin and Allison Ballandras-Colas},
  journal = {PLoS Pathogens},
  year = {2026},
  month = aug,
  doi = {10.1371/journal.ppat.1014449},
  url = {https://cnrs.hal.science/hal-05773831v1},
  note = {CC BY 4.0},
}

RIS

TY  - JOUR
TI  - Nucleocapsid-like cryo-EM structure of influenza B virus
AU  - Marie Thirion
AU  - Alice Stelfox
AU  - Florian Chenavier
AU  - Héléna Chomat
AU  - Catherine Isel
AU  - Lily-Lorette Freslon
AU  - Eleftherios Zarkadas
AU  - Rob Ruigrok
AU  - Nadia Naffakh
AU  - Thibaut Crépin
AU  - Allison Ballandras-Colas
PY  - 2026
DA  - 2026/08/10
JO  - PLoS Pathogens
DO  - 10.1371/journal.ppat.1014449
UR  - https://cnrs.hal.science/hal-05773831v1
AB  - Influenza viruses belong to the Orthomyxoviridae family, they are categorized into four types: A, B, C, and D. Influenza B viruses co-circulate annually with influenza A strains during seasonal flu epidemics in humans, causing severe disease. The segmented RNA encapsidated by multiple copies of the nucleoprotein (NP) and attached to the heterotrimeric polymerase forms the central replicative unit called the viral ribonucleoprotein (vRNP). All influenza NP proteins share the same core domain folding, only NP of influenza B virus (B/NP) has an extended unfolded N-terminal tail of 70 amino-acids. This disordered N-terminal tail is required for nuclear localization of the protein, and may be involved in viral RNA transcription and replication regulation. In this study, we report that in absence of the extended N-terminal tail, the truncated NP maintains RNA binding ability and NP oligomeric state in vitro . We then reconstituted RNP-like particles by incubating truncated B/NP with synthetic RNA and we solved the cryo-EM structure at 4.1 Å resolution. Their morphology appears identical to native vRNPs extracted from viruses when observed by negative-stain electron microscopy. Overall, our results suggest that vRNPs from influenza virus type A, B and D share the same right-handed antiparallel helical conformation and that the B/NP N-terminal tail does not participate to the helical architecture stabilization once the vRNPs are assembled.
SN  - 1553-7366
SN  - 1553-7374
ER  -

Abstract

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