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Review
. 2016 Nov 23;8(11):317.
doi: 10.3390/v8110317.

The Expanding Family of Virophages

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Free PMC article
Review

The Expanding Family of Virophages

Meriem Bekliz et al. Viruses. .
Free PMC article

Abstract

Virophages replicate with giant viruses in the same eukaryotic cells. They are a major component of the specific mobilome of mimiviruses. Since their discovery in 2008, five other representatives have been isolated, 18 new genomes have been described, two of which being nearly completely sequenced, and they have been classified in a new viral family, Lavidaviridae. Virophages are small viruses with approximately 35-74 nm large icosahedral capsids and 17-29 kbp large double-stranded DNA genomes with 16-34 genes, among which a very small set is shared with giant viruses. Virophages have been isolated or detected in various locations and in a broad range of habitats worldwide, including the deep ocean and inland. Humans, therefore, could be commonly exposed to virophages, although currently limited evidence exists of their presence in humans based on serology and metagenomics. The distribution of virophages, the consequences of their infection and the interactions with their giant viral hosts within eukaryotic cells deserve further research.

Keywords: Megavirales; metagenomic; mimivirus; mobilome; virophages.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
The intracellular life cycle of virophages: This scheme summarizes the different steps of the intra-amoebal life cycle of a virophage and its giant viral host. In (1), the giant virus and the virophage enter the amoeba; In (2), the giant virus and the virophage are internalized in vacuoles; The virus factory (VF) appears in (3), followed by the production of virophages and giant virus virions. Finally, the amoeba is lysed and the two types of viruses are liberated (4).
Figure 2
Figure 2
Comparison of conserved gene architectures in the genomes of virophages. MCP: major capsid protein; mCP: minor capsid protein; S3H: DNA helicase/primase; ZnR: zinc-ribbon domain; PRO: cysteine protease; ATPase: putative FtsK-HerA family DNA packaging ATPase; polB: family B DNA polymerase; GIY: GIY-YIG endonuclease/Zn-ribbon.
Figure 3
Figure 3
Phylogeny reconstruction based on the capsid proteins from virophages. The sequences were aligned with the Muscle software [49]; the un-rooted tree was built using the maximum likelihood method.

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