[3] Joining of RNA molecules with RNA ligase

T4 RNA ligase catalyzes the ATP-dependent phosphodiester bond formation between a 5´-terminal phosphate (donor) and a 3´-terminal hydroxyl (acceptor). Although the enzyme can produce circular products with substrates of sufficient length that contain the required termini RNA ligase is also a very effective intermolecular joining reagent for oligonucleotide synthesis. The versatility of RNA ligase as a reagent for oligoribonucleotide synthesis is illustrated by the following two examples. For preparative synthesis, the enzyme readily catalyzes the equimolar joining of two oligoribonucleotide blocks on a moderate scale (ca. 1 μmol) and the enzyme can be used to synthesize small amounts of internally P-labeled oligomers of high specific activity. This chapter discusses applications for oligoribonucleotide synthesis and also explains the use of RNA ligase for the preparation of deoxy oligomers.