An NAD Derivative Produced During Transfer RNA Splicing: ADP-Ribose 1′′-2′′Cyclic Phosphate

Transfer RNA (tRNA) splicing is essential in Saccharomyces cerevisiae as well as in humans, and many of its features are the same in both. In yeast, the final step of this process is removal of the 2′ phosphate generated at the splice junction during ligation. A nicotinamide adenine dinucleotide (NAD)-dependent phosphotransferase catalyzes removal of the 2′ phosphate and produces a small molecule. It is shown here that this small molecule is an NAD derivative: adenosine diphosphate (ADP)-ribose 1"-2" cyclic phosphate. Evidence is also presented that this molecule is produced in Xenopus laevis oocytes as a result of dephosphorylation of ligated tRNA.