Addition of mononucleotides to oligoribonucleotide acceptors with T4 RNA ligase

RNA ligase induced by bacteriophage T4 catalyzed the addition of nucleoside 5',3'-diphosphates to oligoribonucleotide acceptors in the presence of ATP. The reactions proceeded in equimolar concentrations of donors and acceptors. Several oligonucleotides of defined sequence were synthesized by this method in yields of 28-68%. The enzyme required the phosphate ester at the 3' position of the donor molecule, nucleoside 5',2'-diphosphates being unable to serve as donors. Thymidine 5',3'-diphosphate was active as a donor for the enzyme. The ligation product, (Ap)2ApCp, was also obtained from the reaction of (Ap)2A and 5'-adenylylated cytidine 5',3'-diphosphate (A5'pp5'Cp) with RNA ligase in the absence of ATP. These results show that the minimal substrate for RNA ligase is a nucleoside 5',3'-diphosphate.