RNA Ligase

Definition

RNA ligases are enzymes that catalyze formation of a covalent linkage between two oligoribonucleotides via a phosphodiester bond. In the context of the “RNA world” hypothesis, this linkage reaction would have been of great importance to generate longer, more complex RNA molecules from shorter oligonucleotides, which are easier to synthesize from mononucleotides.

Overview

Because no dedicated RNA ligase ribozymes had been found in nature, the SELEX technology was applied to isolate artificial ribozymes from a combinatorial library of random RNA. The identified ribozymes catalyze the bond formation of a 5′-triphosphorylated RNA to the 3′-hydroxyl group of a second RNA molecule forming the natural 3–5′ phosphodiester linkage (Bartel and Szostak 1993):

$$ 5^{\prime }-{\mathrm{RNA}}_{(1)}-\mathrm{O}\mathrm{H}+5^{\prime }-\mathrm{P}\mathrm{P}\mathrm{P}-{\mathrm{RNA}}_{(2)}\to 5^{\prime }-{\mathrm{RNA}}_{(1)}-\mathrm{P}-{\mathrm{RNA}}_{(2)}+\mathrm{P}\mathrm{P} $$

These ribozymes...