title: Thirty-thousand-year-old distant relative of giant icosahedral DNA viruses with a pandoravirus morphology.
abstract: The largest known DNA viruses infect Acanthamoeba and belong to two markedly different families. The Megaviridae exhibit pseudo-icosahedral virions up to 0.7 μm in diameter and adenine-thymine (AT)-rich genomes of up to 1.25 Mb encoding a thousand proteins. Like their Mimivirus prototype discovered 10 y ago, they entirely replicate within cytoplasmic virion factories. In contrast, the recently discovered Pandoraviruses exhibit larger amphora-shaped virions 1 μm in length and guanine-cytosine-rich genomes up to 2.8 Mb long encoding up to 2,500 proteins. Their replication involves the host nucleus. Whereas the Megaviridae share some general features with the previously described icosahedral large DNA viruses, the Pandoraviruses appear unrelated to them. Here we report the discovery of a third type of giant virus combining an even larger pandoravirus-like particle 1.5 μm in length with a surprisingly smaller 600 kb AT-rich genome, a gene content more similar to Iridoviruses and Marseillevirus, and a fully cytoplasmic replication reminiscent of the Megaviridae. This suggests that pandoravirus-like particles may be associated with a variety of virus families more diverse than previously envisioned. This giant virus, named Pithovirus sibericum, was isolated from a >30,000-y-old radiocarbon-dated sample when we initiated a survey of the virome of Siberian permafrost. The revival of such an ancestral amoeba-infecting virus used as a safe indicator of the possible presence of pathogenic DNA viruses, suggests that the thawing of permafrost either from global warming or industrial exploitation of circumpolar regions might not be exempt from future threats to human or animal health.
authors.affiliation: Structural and Genomic Information Laboratory, Unité Mixte de Recherche 7256 (Institut de Microbiologie de la Méditerranée) Centre National de la Recherche Scientifique, Aix-Marseille Université, 13288 Marseille Cedex 9, France.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Legendre
authors.forename: Julia
authors.initials: J
authors.lastname: Bartoli
authors.forename: Lyubov
authors.initials: L
authors.lastname: Shmakova
authors.forename: Sandra
authors.initials: S
authors.lastname: Jeudy
authors.forename: Karine
authors.initials: K
authors.lastname: Labadie
authors.forename: Annie
authors.initials: A
authors.lastname: Adrait
authors.forename: Magali
authors.initials: M
authors.lastname: Lescot
authors.forename: Olivier
authors.initials: O
authors.lastname: Poirot
authors.forename: Lionel
authors.initials: L
authors.lastname: Bertaux
authors.forename: Christophe
authors.initials: C
authors.lastname: Bruley
authors.forename: Yohann
authors.initials: Y
authors.lastname: Couté
authors.forename: Elizaveta
authors.initials: E
authors.lastname: Rivkina
authors.forename: Chantal
authors.initials: C
authors.lastname: Abergel
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Claverie
mesh_terms: D000656:Amoeba / Q000821:virology*; D001483:Base Sequence; D016000:Cluster Analysis; D019295:Computational Biology; D004267:DNA Viruses / Q000145:classification / Q000235:genetics* / Q000648:ultrastructure*; D020869:Gene Expression Profiling; D008854:Microscopy, Electron; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D010802:Phylogeny; D040901:Proteomics; D017422:Sequence Analysis, DNA; D012800:Siberia; D012988:Soil Microbiology
keywords: giant DNA virus; icosahedral capsid; late Pleistocene