Viruses melt ‘glassy ’ DNA

US Researchers have identified the factors that enable viral DNA to turn from solid to liquid, which allows them to infect host cells. They say the process could become a target for new antiviral therapies. The DNA inside a virus’s protein shell is packed much more densely than in the nucleus of a human cell. Recent research has shown that due to the tight packing and the mutual repulsion of the negative charges on the DNA’s phosphate groups, the chain can hardly move. Earlier this year,Douglas Smith and colleagues at the University of California at San Diego analysed the mechanisms of the packing process driven by a motor protein and demonstrated that the packaged DNA of an inactive virus exhibits non-equilibrium or ‘glassy ’ dynamics. 1 Yet during infection, viruses can inject their DNA like a liquid into the host cell at high speed. So how can the pressurised, frozen DNA suddenly become liquid enough for this to happen? A group led by Alex Evilevitchat Carnegie Mellon University has worked out the mechanism for this process in two unrelated types of virus. For th