Enzymatic conversion of 5'-phosphate-terminated RNA to 5'-di- and triphosphate-terminated RNA.

Abstract

From vaccinia virus cores, an enzyme, 5''-phosphate-polyribonucleotide kinase, was isolated that in the presence of ATP and Mg2+ catalyzes the conversion of 5''-phosphate and 5''-diphosphate termini of RNA to the 5''-triphosphate species. With the exception of dATP, other nucleoside triphosphates were inactive as phosphate donors; activity with dATP was 10% of that observed with ATP. The purified enzyme did not phosphorylate 5''-hydroxyl- or 5''-monophosphate-terminated polydeoxyribonucleotides, although a variety of 5''-monophosphate-terminated RNA chains were active as phosphate acceptors. By using a coupled system of 5''-phosphate-polyribonucleotide kinase and guanylyltransferase in the presence of ATP, GRP, Mg2+ and S-adenosylmethionine, capping of 5''-P-, 5''-PP- and 5''-PPP-RNA was demonstrated; in the absence of 5''-phosphate-polyribonucleotide kinase only 5''-PPP-RNA was capped by guanylyltransferase.