Fig. 5.

Coronavirus NendoU activity produces molecules with 2′-3′ cyclic phosphate termini. Ligation of 5′-[³²P]pCp with the 3′ terminus of coronavirus nsp15 cleavage products using T4 RNA ligase requires pretreatment with PNK that (in contrast to CIP) is capable of removing 2′-3′ cyclic phosphates. Reaction products were analyzed by denaturing PAGE and autoradiography. Lane 1, ligation reaction with control RNA m4; lanes 2-4, ligation reactions with purified 5′-terminal nsp15 cleavage product without further treatment (lane 2) and after treatment with PNK (lane 3) or CIP (lane 4).