An RNA ligase from wheat germ which participates in transfer RNA splicing in vitro

Transfer RNA half-molecules are intermediates in the splicing of tRNA precursors containing intervening sequences. We have utilized yeast tRNA half-molecules to identify and partially purify an ATP-dependent RNA ligase activity from extracts of wheat germ. This activity can complement a yeast tRNA endonuclease in vitro to efficiently splice 10 different yeast tRNA precursors. The products of in vitro splicing are a covalently joined tRNA and a circular intervening sequence RNA. The internucleotide bond formed at the splice junction is a 2'-phosphomonoester, 3',5'-phosphodiester structure. The 2'-phosphate originates from the 2',3'-cyclic phosphate at the 3' terminus of the 5' half-tRNA. The phosphodiester phosphate is derived from the gamma-phosphate of ATP.