PT  - JOURNAL ARTICLE
AU  - Alejandro Villalta
AU  - Alain Schmitt
AU  - Leandro F. Estrozi
AU  - Emmanuelle R. J. Quemin
AU  - Jean-Marie Alempic
AU  - Audrey Lartigue
AU  - Vojtěch Pražák
AU  - Lucid Belmudes
AU  - Daven Vasishtan
AU  - Agathe M. G. Colmant
AU  - Flora A. Honoré
AU  - Yohann Couté
AU  - Kay Grünewald
AU  - Chantal Abergel
TI  - The giant Mimivirus 1.2 Mb genome is elegantly organized into a 30 nm helical protein shield
AID  - 10.1101/2022.02.17.480895
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.02.17.480895
4099  - http://biorxiv.org/content/early/2022/02/18/2022.02.17.480895.short
4100  - http://biorxiv.org/content/early/2022/02/18/2022.02.17.480895.full
AB  - 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.One-Sentence Summary Mimivirus genome organization in the icosahedral virion.Competing Interest StatementThe authors have declared no competing interest.