The giant mimivirus 1.2 Mb genome is elegantly organized into a 30 nm diameter helical protein shield
- Aix-Marseille University, CNRS-AMU UMR7256, France
- Univ. Grenoble Alpes, CNRS, CEA,, France
- University of Hamburg, Germany
- Université Grenoble Alpes, France
Abstract
Mimivirus is the prototype of the Mimiviridae family of giant dsDNA viruses. Little is known about the organization of the 1.2 Mb genome inside the membrane-limited nucleoid filling the ~0.5 µm icosahedral capsids. Cryo-electron microscopy, cryo-electron tomography and proteomics revealed that it is encased into a ~30 nm diameter helical protein shell surprisingly composed of two GMC-type oxidoreductases, which also form the glycosylated fibrils decorating the capsid. The genome is arranged in 5- or 6-start left-handed super-helices, with each DNA-strand lining the central channel. This luminal channel of the nucleoprotein fiber is wide enough to accommodate oxidative stress proteins and RNA polymerase subunits identified by proteomics. Such elegant supramolecular organization would represent a remarkable evolutionary strategy for packaging and protecting the genome, in a state ready for immediate transcription upon unwinding in the host cytoplasm. The parsimonious use of the same protein in two unrelated substructures of the virion is unexpected for a giant virus with thousand genes at its disposal.
Data availability
Mimivirus reunion genome has been deposited under the following accession number: BankIt2382307 Seq1 MW004169.3D reconstruction maps and the corresponding PDB have been deposited to EMDB (Deposition number Cl1a: 7YX4, EMD-14354; Cl1a focused refined: D_1292117739; Cl3a: 7YX5, EMD-14355; Cl2: 7YX3, EMD-14353).The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD021585 and 10.6019/PXD021585.The tomograms have been deposited in EMPIAR under accession number 1131 and tomograms video are provided with the article.
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Author details
Funding
European Research Council (832601)
- Chantal Abergel
Agence Nationale de la Recherche (ANR-16-CE11-0033-01)
- Chantal Abergel
Agence Nationale de la Recherche (ANR-10-INBS-08-01)
- Yohann Couté
Agence Nationale de la Recherche (ANR-17-EURE-0003)
- Yohann Couté
Wellcome Trust (107806/Z/15/Z)
- Kay Grünewald
Deutsche Forschungsgemeinschaft (INST 152/772-1|152/774-1|152/775-1|152/776-1)
- Kay Grünewald
Alexander von Humboldt-Stiftung (FRA 1200789 HFST-P)
- Emmanuelle RJ Quemin
Agence Nationale de la Recherche (ANR-10-INBS-04)
- Chantal Abergel
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2022, Villalta 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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The giant mimivirus 1.2 Mb genome is elegantly organized into a 30 nm diameter helical protein shield
eLife 11:e77607.
https://doi.org/10.7554/eLife.77607
