When a virus infects a cell, the cell often turns on genes for molecules known as heat-shock proteins. Is this reaction part of a cell’s defense against viruses, an unintended result of viral action, or something that the virus deliberately does to aid itself?
Studies of a gene from a bird virus suggest that it’s the last answer—a self-serving action by the virus. Jolanta B. Glotzer of the Institute for Molecular Pathology in Vienna, Austria, and her colleagues found that introducing this gene into bird cells promoted the production of two heat-shock proteins. The researchers then created a form of the virus lacking the gene. This mutant virus couldn’t replicate within untreated bird cells, the scientists report in the Sept. 14 Nature. In cells warmed to create heat-shock proteins, however, the mutant virus was able to make copies of itself.
It’s still not clear why this virus and presumably others need to turn on their host’s genes for heat-shock proteins. One potential reason is that the proteins can stop cells from committing suicide, which might give a virus more time to replicate within the cell. Or perhaps the heat-shock proteins, which normally help other cellular proteins fold into their appropriate shapes, provide the same service for viral proteins.