Action of Pennisetum typhoides double-stranded ribonuclease on viral ds RNAs.

A ribonuclease that preferentially cleaves natural and synthetic double-stranded (ds) RNAs has been partially purified from Pennisetum typhoides. The enzyme degrades [3H]poly(rA) X poly(rU) to acid-soluble products. The ds RNase does not degrade RNA:DNA hybrid but appears to have about 18% activity against single-stranded (ss) RNAs under the assay conditions used for the cleavage of ds RNAs. The RNase has a molecular weight of 35,000 daltons as determined from gel filtration using Sephadex G-200. The ds RNase shows an absolute requirement for divalent cations Mg++ or Mn++ and monovalent cations K+ or Na+. The specificity of the enzyme towards ds RNA template is supported by the inhibition of cleavage of ds RNAs by ethidium bromide and Penicillium chrysogenum viral ds RNA. The enzyme preparation acts on ds RNAs isolated from Saccharomyces cerevisiae and P. chrysogenum virus. The purified ds RNase also cleaves the in vitro transcriptional products of adenovirus DNA and this activity is inhibited by 5 mM ethidium bromide suggesting that ds regions of adenovirus RNA are involved in the cleavage process.