To dephosphorylate viral 59 triphosphate RNA, calf intestine alkaline phosphatase (CIAP) (Fermentas) was used. Briefly, RNA was isolated using Trizol according to manufacturer's instructions. For dephosphorylation the reaction mix was set up in a 50 ml volume with 50 mg RNA, 25 U CIAP and 80 U RiboLock RNase inhibitor (Fermentas) and was incubated for 3 h at 42uC. Thereafter the RNA was isolated using the RNeasy mini Kit from Qiagen. RNAs used as control were mock-treated replacing CIAP by glycerol.