1. Department of Virology, Biological Faculty; Moscow State University; Moscow 119234 Russia
2. A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University; Moscow 119992 Russia
3. N. I. Vavilov Institute of General Genetics, Russian Academy of Science; Moscow 119991 Russia
4. Centre National de la Recherche Scientifique; Institut de Biologie Moléculaire des Plantes (IBMP); Strasbourg 67084 France