Double-stranded ribonuclease activities from HeLa cell nuclei

Degradation of poly(I)·[³H] poly(C) to acid-soluble products is observed with a nuclear lysate from HeLa cells. Most of the activity is lost after Sephadex G-100 chromatography, but can be regained by mixing two fractions, FI and FII, that elute separately. FII has been further purified by chromatography on DEAE-cellulose and phosphocellulose, and is then totally dependent on FI for any activity with poly(I)·poly(C). However, FII retains some activity with poly(C); and in the presence of FI, it can be substituted by purified $\text{E. coli}$ RNase II for the degradation of poly(I)·poly(C). Thus, at least two macromolecular components participate in the bulk degradation of poly(I) poly(C) in HeLa nuclear lysates, and one of them may be a single-stranded exonuclease.