5'-RNA self-capping from guanosine diphosphate.

A selected RNA (isolate 6) efficiently catalyzes a self-capping reaction with free GDP, yielding the same 5'-capped structure as is formed by protein GTP:RNA guanylyltransferase. This unexplored RNA-catalyzed reaction type involving nucleophilic attack on phosphate by phosphate adds to the variety of possible postsynthetic RNA-catalyzed RNA modifications. The selected RNA requires only Ca2+ for activation and has a broad active pH range of 4.5-9.0. The RNA also has a 5'-pyrophosphatase activity.