Biomaterial Database

Separation and characterization of two activities from HeLa cell nuclei that degrade double-stranded RNA. 1978

B K Saha, and D Schlessinger

Two enzymatic activities that degrade double-stranded RNA have been partially purified from HeLa cell nuclei using reoviral [3H]RNA as the substrate. The two active fractions, separated by chromatography on phosphocellulose, are designated PC I and PC II. Both fractions degrade a variety of double-stranded RNAs with an absolute requirement for a divalent cation. However, they are distinct by at least five criteria. 1)PC I degrades a variety of single- and double-stranded RNAs, single- and double-stranded DNAs, and DNA.RNA hybrids, in addition to double-stranded reoviral RNA. In contrast, PC II has maximal activity with reoviral RNA, some activity with rRNA, and much less activity with the other substrates. 2) Analyses of reaction products by sucrose gradient centrifugation and chromatography on Sephadex G-100 and DEAE-cellulose indicate that, PC I cleaves reoviral RNA endonucleolytically to a final mixture of mono- and oligonucleotides, whereas the only acid- or alcohol-soluble products of PC II are 5'-XMPs produced exonucleolytically. 3) PC I activity is stimulated 2-fold more by MnCl2 than by MgCl2, whereas PC II activity is stimulated 3-fold more by MgCl2 than by MnCl2. 4) PC I activity is inhibited by NaCl concentrations as low as 10 mM, whereas PC II requires 50 to 80 mM NaCl for optimal activity. 5)Estimated by their sedimentation rates in glycerol gradients, PC I and PC II have apparent molecular weights of 55,000 and 20,000, respectively.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D002467	Cell Nucleus	Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)	Cell Nuclei,Nuclei, Cell,Nucleus, Cell
D002499	Centrifugation, Density Gradient	Separation of particles according to density by employing a gradient of varying densities. At equilibrium each particle settles in the gradient at a point equal to its density. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Centrifugations, Density Gradient,Density Gradient Centrifugation,Density Gradient Centrifugations,Gradient Centrifugation, Density,Gradient Centrifugations, Density
D002845	Chromatography	Techniques used to separate mixtures of substances based on differences in the relative affinities of the substances for mobile and stationary phases. A mobile phase (fluid or gas) passes through a column containing a stationary phase of porous solid or liquid coated on a solid support. Usage is both analytical for small amounts and preparative for bulk amounts.	Chromatographies
D006367	HeLa Cells	The first continuously cultured human malignant CELL LINE, derived from the cervical carcinoma of Henrietta Lacks. These cells are used for, among other things, VIRUS CULTIVATION and PRECLINICAL DRUG EVALUATION assays.	Cell, HeLa,Cells, HeLa,HeLa Cell
D012260	Ribonucleases	Enzymes that catalyze the hydrolysis of ester bonds within RNA. EC 3.1.-.	Nucleases, RNA,RNase,Acid Ribonuclease,Alkaline Ribonuclease,Ribonuclease,RNA Nucleases,Ribonuclease, Acid,Ribonuclease, Alkaline
D012313	RNA	A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. (Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)	RNA, Non-Polyadenylated,Ribonucleic Acid,Gene Products, RNA,Non-Polyadenylated RNA,Acid, Ribonucleic,Non Polyadenylated RNA,RNA Gene Products,RNA, Non Polyadenylated
D012367	RNA, Viral	Ribonucleic acid that makes up the genetic material of viruses.	Viral RNA
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities