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  • Title: Isolation and purification of double-stranded ribonuclease from calf thymus.
    Author: Ohtsuki K, Groner Y, Hurwitz J.
    Journal: J Biol Chem; 1977 Jan 25; 252(2):483-91. PubMed ID: 833140.
    Abstract:
    A RNase from calf thymus, which specifically cleaves native or synthetic double-stranded RNA molecules endonucleolytically, has been isolated and purified from calf thymus. For optimal activity, the enzyme requires a sulfhydryl reagent and divalent cations; over 95 per cent of the activity is inhibited by 0.5 mm ethidium bromide. The degradation of [3H]poly(C)-poly(I) by purified enzyme preparations yields labeled dinucleotides and octanucleotides; the latter oligonucleotide contained 5'-phosphate and 3'-hydroxyl termini. The enzyme cleaves high molecular weight RNAs such as RNA products formed in vitro by T3 phage-induced RNA polymerase from T3 phage DNA, heterogeneous RNA isolated from duck reticulocyte nuclei, and 45 S RNA isolated from rat liver nucleoli. The mode of degradation of RNA in vitro with the double-stranded RNase is similar to that of Escherichia coli RNase III and appears to act endonucleolytically. The degradation of 45 S RNA with the enzyme results in the production of 29 S and 19 S RNA fragments. These findings suggest that the enzyme may be involved in the processing of high molecular weight precursor RNAs to mRNA or rRNAs in a manner analogous to that reported for RNase III of E. coli.
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