title: Nuclear location of ribonuclease H and increased level of magnesium-dependent ribonuclease H in rat liver on thioacetamide treatment.
abstract: Rat liver nuclei were isolated in aqueous solutions of low ionic strength or anhydrous glycerol. The presence of ribonuclease H (RNase H) [EC 3.1.4.34] activity in the cytoplasm is due to extraction of the nuclear enzyme by buffer and inorganic salts. Two forms of RNase H were separated from rat liver nuclei by affinity chromatography using a DNA-cellulose column. When the RNase H in the wash solution of nuclei with 0.3 M sucrose and in nuclear solution extracted with 0.15 M NaCl were fractionated on a single-stranded DNA-cellulose column, two peaks corresponding to Mn2+- and Mg2+-dependent RNases H were eluted at 0.1 M and 0.2 M NaCl, respectively, and a peak having both RNase H activities was recovered in the wash-through fraction from the column. Among the enzymes from these two fractions in the nuclei, the activity of the Mg2+-dependent RNase H which binds to DNA-cellulose increased several-fold within 24 h of a single injection of thioacetamide. The activities of Mg2+-dependent RNase H extracted with higher-salt solution from the nuclei and recovered in the flow-through fraction from the DNA-cellulose column and the Mn2+-dependent RNase H activities were relatively unaffected by an injection of thioacetamide.
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology*; D004720:Endonucleases / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D016914:Ribonuclease H; D012260:Ribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D013853:Thioacetamide / Q000494:pharmacology*
chemical_list: D000081:Acetamides; D013853:Thioacetamide; D004720:Endonucleases; D012260:Ribonucleases; D016914:Ribonuclease H; D008274:Magnesium