Partial purification and characterization of a double-stranded RNA-specific nuclease from human placenta

Abstract

A double-stranded RNA-specific nuclease (ds R Nase) has been isolated and partially purified from human placenta by DEAE-cellulose and DNA-cellulose column chromatography. Denatured DNA-cellulose retained most of the single-stranded RNA-specific nuclease (ss R Nase) activity, whereas the ds R Nase came out in the void volume. N-ethylmaleimide at a concentration of 5 mM, selectively inhibited ds R Nase activity by 60% under the conditions in which the ss R Nase activity was inhibited to an extent of 7%. The ds R Nase was specifically inhibited byPenicillium chrysogenum viral ds RNA and by ethidium bromide. The partially purified ds R Nase showed requirements for Mg²⁺ whereas Mn²⁺ and NH₄⁺ ions were inhibitory. The DEAE-enzyme cleaved ³²P-labelled 45S ribosomal precursor RNAs from Yoshida ascites sarcoma cells into species that had similar electrophoretic mobilities as the mature rRNAs.