Specific RNA-cleaving activities from HeLa cells.

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Abstract
Subcellular fractionation of [human cervical carcinoma] HeLa cells was carried out under gentle conditions to isolate enzymes that cleave RNA precursors in a specific manner. Four separate activities-cleavage of HeLa cell heterogeneous nuclear RNA, the HeLa cell 45S rRNA precursor, RNA.cntdot.DNA hybrids (RNase H) and the Escherichia coli tRNATyr precursor (RNase P)-were revealed by these studies. The specificity and limited nature of these cleavages suggest that they are due to eukaryotic RNA-processing enzymes. The virtual absence oi random nucleases from these enzymes was demonstrated by their inability to cleave the 8000-base early mRNA precursor of bacteriophage T7, E. coli 30S rRNA precursor on HeLa cytoplasmic poly(A)-containing RNA.