Partial purification of RNase P from Schizosaccharomyces pombe

Ribonuclease P from the fission yeast Schizosaccharomyces pombe was partially purified using DEAE-cellulose and phosphocellulose column chromatography. The yeast RNase P enzyme cleaves Escherichia coli tRNATyr precursor to give tRNATyr containing its mature 5' end. The enzyme activity is inhibited after treatment with nucleases; this indicates the requirement of a nucleic acid component for activity. The enzyme purification was greatly facilitated by using a synthetically prepared radioactive ApApApCOH ligated to the 5'-terminal phosphate of E. coli tRNAfMet (ApApApCp-tRNA) substrate. (p denotes a [32P]phosphate group.) This substrate was cleaved by yeast RNase P to the mature tRNA and a tetranucleoside triphosphate ApApApCOH. The synthetic substrate allowed the utilization of a simple assay procedure measuring the trichloroacetic acid solubility of the ApApApC product, thus avoiding the more cumbersome gel electrophoric separation of reaction products.