On the cover of Cell!

▎WuXi AppTec Content Team Editor What does the virus look like in your mind? The viruses we are familiar with are often either icosahedral similar to a sphere (represented by adenovirus); or a helical column such as tobacco mosaic virus
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In addition, there are some complex viruses that have both properties, such as bacteriophages
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However, these forms are not all of the virus
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In some hidden corners of the earth with extremely harsh environments, scientists have found more viruses with strange shapes that can infect archaea.
Spindle virus is one of them
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Where do these viruses with sharp ends and plump in the middle, shaped like lemons, come from? ▲ Schematic diagram of spindle-shaped virus and other forms of viruses in a near-boiling acidic volcanic hydrothermal environment (Image source: Egelman lab at UVA) Recently, a team led by the University of Virginia and the Pasteur Institute in France published a paper The evolutionary path of spindle virus was revealed in
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The authors point out that these viruses evolved from columnar viruses, and the change in morphology gave them a huge survival advantage
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The study was also selected as the cover article of the latest issue of Cell
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"We now recognize a new model to explain how proteins make up the capsids that viruses use to package DNA," said corresponding author Edward H.
Egelman, professor of medicine at the University of Virginia School of Medicine.
"This discovery could help not only Our understanding of how specific viruses evolve may also provide new avenues for drug and vaccine delivery
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" The study analyzed Sulfolobus single-tailed virus 1 (SMV1), a virus whose host lives in 75~ In acidic volcanic hydrothermal fluids at 90°C
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These viruses, which live in extreme environments that are almost boiling, have a magical property: one end of their spindle-shaped bodies grows a "tail"
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The research team points out that this structure likely explains how ancient columnar viruses evolved into today's spindle shape
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The study used cryo-electron microscopy to obtain the atomic structure of the SMV1 protein capsid
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They found that a highly hydrophobic protein is likely integrated into the host's cell membrane before viral particle assembly, forming seven protein chains that slide between the spindle virus body and tail
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▲ The cryo-electron microscope structure of SMV1 (image source: Reference [1]) It is precisely because of these protein chains that SMV1 no longer has a fixed shape, they are like puffer fish: as the diameter of the helical column changes, the capsid of the virus " expand" into a near spherical shape, thereby providing more space for the genetic material
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At the same time, these protein strands form an impassable barrier to keep the surrounding acid from entering and damaging the virus' DNA
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Thus, this study suggests that today's spindle-shaped viruses likely evolved from ancient columnar ancestors
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These columnar viruses contain very limited DNA, and the transformation of the protein capsid to a spindle shape allows SMV1 to pack more genetic material than its ancestors
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From an evolutionary point of view, it is undoubtedly an extremely important change to carry a larger genome
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▲Schematic diagram of the transformation from columnar virus to spindle virus (Image source: Reference [1]) Professor Egelman concluded: "It is very important for us to understand how viruses evolve
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But we can also learn from viruses, and based on These simple structures develop new technologies
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"Reference: [1] Fengbin Wang et al, Spindle-shaped archaeal viruses evolved from rod-shaped ancestors to package a larger genome, Cell (2022).
DOI: https://doi.
org/10.
1016/j.
cell.
2022.
02.
019[2] Shapeshifting volcano virus points to new ways to deliver drugs, vaccines.
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