"Repairs 3'-OH/5'-PO4 nicks in duplex RNA or RNA:DNA hybrid in which the broken 3'-OH strand is RNA. The nick ligation reaction entails three nucleotidyl transfer steps. In the first step, the RNA ligase reacts with ATP in the absence of nucleic acid to form a covalent ligase-AMP intermediate and release pyrophosphate. In step 2, the ligase-AMP binds to the nicked duplex nucleic acid and transfers the adenylate to the 5'-PO4 terminus to form an adenylylated nicked intermediate. In step 3, the RNA ligase directs the attack of the nick 3'-OH on the 5'-phosphoanhydride linkage, resulting in a repaired 3' - 5' phosphodiester and release of AMP."xsd:string