A possible role of lipids in RNA polymerase from mammalian cells

The effects of treatment with phospholipases and extraction with solvents on the activities of RNA polymerases from several rat tissues were studied. The RNA polymerase activity of particulate enzyme from rat liver nuclei was decreased by pretreatment of the enzyme with phospholipase A. The phospholipase decreased the RNA polymerase activity in presence of Mg2+ but not that in presence of Mn2+. The effect of phospholipase A was observed only at low ionic concentration. When the RNA polymerase activity was determined in presence of ammonium sulfate, KCl, or NaCl, phospholipase A did not decrease the RNA polymerase activity. Extraction of the RNA polymerase with ether or iso-octane decreased the RNA polymerase activity to approximately the same extent as the pretreatment with phospholipase A. Phospholipase C produced similar changes as phospholipase A but phospholipase D and lipase did not have any effect on the RNA polymerase activity. Treatment with phospholipase A as well as extraction with solvents enhanced the activity of chromatin-bound RNA polymerase from rat brain, and the RNA polymerase activities of similar preparations from spleen, kidney, heart, and lung were affected only to a relatively smaller extent.

Transcription in yeast: separation and properties of multiple FNA polymerases

Four peaks of DNA-directed RNA polymerase activity are resolved by salt gradient elution of a sonicated yeast cell extract on DEAE-Sephadex. The enzymes, which are named IA, IB, II, and III in order of elution, all appear to come from cell nuclei. Only enzyme II is sensitive to alpha-amanitin. All enzymes are more active with Mn(++) than with Mg(++) as divalent ion. Enzymes IB and II have salt optima in the range 0.05-0.10 M (NH(4))(2)SO(4), whereas enzyme III is maximally active at 0.20-0.25 M (NH(4))(2)SO(4). With optimal salt concentration and saturating DNA, the template preference ratio, activity on native calfthymus DNA divided by activity on denatured calf-thymus DNA, is 2.2 for IB, 0.4 for II, and 3.5 for III. None of the yeast polymerases was inhibited by rifamycin SV. Rifamycin AF/013 effectively inhibited polymerases IB, II, and III.

3-Cyclic amine derivatives of rifamycin: strong inhibitors of the DNA polymerase activity of RNA tumor viruses

Derivatives of rifamycin-SV with substituted cyclic-amine side chains in position 3 of the ansa ring are strong inhibitors of RNA-directed DNA and DNA-directed DNA polymerase activity of RNA tumor viruses of murine, feline, and avian origin. Among 37 3-amine derivatives of rifamycin-SV that were tested, 29 3-cyclic amine derivatives were good inhibitors of the viral polymerases. Especially active were 3-piperidyl derivatives of rifamycin-SV with cyclohexyl and cyclohexylalkyl substituents. Derivatives that were effective against the viral polymerase also blocked cell transformation by the murine sarcoma virus. A DNA-directed DNA polymerase preparation from human KB cells was less sensitive to inhibition by these derivatives than the virion polymerase.