EXPRESSION OF MAMMALIAN ANTIVIRAL ENZYMES FROM THE 2-5A SYSTEM IN TRANSGENIC PLANTS

The 2-5A system is an interferon-regulated antiviral RNA decay pathway present in cells of higher vertebrates, Two enzymes are essential, a 2-5A synthetase which produces 5'-phosphorylated, 2',5'-linked oligoad enylates (2-5A) in response to double-stranded RNA, and the 2-5A-depen dent RNase L. To determine if these human proteins would be functional in plants, we expressed the human cDNAs for a 2-5A synthetase and RNa se L in separate tobacco plants. Both proteins were enzymatically acti ve in extracts of transgenic plants while such activities were not det ected in the control plants. Furthermore, activation by 2-5A of RNase L in the transgenic plant leaves was shown to cause degradation of rib osomal RNA. The requirement for both the synthetase and RNase L for an tiviral activity was underscored by the observations that expression o f human RNase L alone or 5-SA-synthetase alone was insufficient to pro tect plants against either tobacco etch virus or tobacco mosaic virus.