Flu Enzyme's Thieving Ways

Structural detective work has fingered a protein thief that precipitates flu infections, an advance that could lead to new flu drugs. Influenza viruses use their RNA polymerase enzymes to steal short tags from the host's RNA. They then use those tags to commandeer the host's protein synthesis machinery for making viral proteins. However, researchers don't understand how each part of the polymerase contributes to the operation. Now, two independent teams have discovered that a portion of a polymerase subunit called PA acts as an endonuclease, which is the enzyme responsible for snipping the tags off the host's RNA. Stephen Cusack, Rob W. H. Ruigrok, and coworkers at the European Molecular Biology Laboratory and the University of Grenoble, both in France, identified the culprit when they solved the X-ray crystal structure of PA from a seasonal flu virus (Nature, DOI: 10.1038/nature07745). Zihe Rao of Tsinghua University, Yingfang Liu of the Chinese Academy of Sciences, both in Beijing, and colleagues reached the same conclusion, examining the corresponding portion of avian flu (Nature, DOI: 10.1038/nature07720).