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News

Immensely high internal pressure in Herpes virus facilitates DNA ejection from capsid.


 

A new study reveals a key mechanism for viral infection that has been highly preserved in viruses that release their genome into the cell nucleus without disassembling the capsid. The study was conducted by Bauer et al at Carnegie Mellon University on the Herpes Virus (HSV-1), one of the most studied viruses with this kind of an infection mechanism. For the first time, it brings into light the presence of high internal pressure of tens of atmospheres due to an extremely condensed genome in a human eukaryotic virus like HSV-1

HSV-1 packages the genome into a thousand times small capsid that is on the nanometer scale creating immense amount of force and stress. This is overcome by the energies produced by the DNA packaging motors while packaging the genome. This energy is ultimately responsible for the internal pressure that results into forceful DNA ejection making it nearly a passive process of ejection. Bauer et al study this by using an osmotic stress agent PEG 8000 to osmotically suppress DNA ejection and as a result find the pressure within the capsid. They found that the osmotic pressure outside was balanced by an internal capsid pressure of approximately 18 atm. Towards the end of the process of DNA ejection, any remaining DNA was either found to be pushed out by enzymatic action or by the osmotic pressure generated within the capsid due to a higher concentration outside in the cell nucleus.

This new study gives an insight into an evolutionarily fixed mechanism that can now be targeted by antiviral drugs. Until now, targeting of nucleotide sequences coding for proteins was difficult due to their constant mutation which led to infections like Herpes being incurable. It also gives more ideas to find evolutionarily similar properties and constant mechanisms in viruses like HIV. It gives hope to cure infections that have been fatal for quite a while.