432: Echovirus 18: Capsid opening releases the genome

Mukhamedova L et al., Proceedings of the National Academy of Sciences - Using cryo-electron tomography and single-particle cryo-EM of infected Cos-7 cells, the authors show that echovirus 18 (E18) releases its RNA in vivo by capsid opening with loss of one to three pentamers. Binding to the neonatal Fc receptor (FcRn) expels VP1 pocket factors and primes particles for uncoating. Activated intermediates were not detected in cells, indicating rapid genome release. Key terms: echovirus 18, enterovirus, genome release, capsid opening, FcRn.

Study Highlights:
Cryo-EM/ET of infected cells resolved genome-containing E18 particles to 4.3 Å and imaged empty and open capsids in situ. Binding of E18 to FcRn induces partial expulsion of VP1 pocket factors, consistent with receptor- triggered priming. Empty capsids observed inside cells lack one to three pentamers of capsid proteins, providing direct evidence of capsid opening as the genome release mechanism. Activated particles were not detected in cells, implying these intermediates are short- lived and genome release is rapid.

Conclusion:
Capsid opening is the physiological uncoating mechanism of echovirus 18 in infected cells: receptor (FcRn) binding expels pocket factors and primes particles, and genome release occurs rapidly via loss of one to several pentamers with empty, incomplete capsids observed in situ.

Music:
Enjoy the music based on this article at the end of the episode.

Article title:
Particles of echovirus 18 open to release their genomes in vivo

First author:
Mukhamedova L

Journal:
Proceedings of the National Academy of Sciences

DOI:
10.1073/pnas.2601182123

Reference:
Mukhamedova L., Buchta D., Hrebík D., et al. Particles of echovirus 18 open to release their genomes in vivo. PNAS. 2026;123(30):e2601182123. https://doi.org/10.1073/pnas.2601182123

License:
This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/

Support:
Base by Base is independent and ad-free — no sponsors, no paywall. If an episode was worth your time, chip in and keep the papers audited and the original songs coming:
❤️ Support monthly: https://buy.stripe.com/cNifZhclVebvagk2JDgEg01
☕ One-time donation: https://donate.stripe.com/7sY4gz71B2sN3RWac5gEg00
More at basebybase.com

On PaperCast Base by Base you'll discover the latest in genomics, functional genomics, structural genomics, and proteomics.

Episode link: https://basebybase.com/episodes/echovirus-18-capsid-opening-432

QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2026-07-23.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited the transcript sections describing E18 structure, FcRn binding and pocket-factor expulsion, endosomal acidification and detachment, in vivo evidence of empty/open capsids, and the genome release mechanism.
- transcript topics: Echovirus 18 capsid structure and pocket factor; FcRn receptor binding and pocket-factor expulsion; Endocytosis and endosomal acidification as uncoating trigger; In vivo evidence: genome-containing particles lack pocket factors; Capsid opening with loss of one to three pentamers; Endosome rupture and cytoplasmic delivery of RNA

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 5
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- In vivo, echovirus 18 genome release...