High salt effect on RNA synthesis in Krebs ascites tumor cells

The incubation of Krebs ascites tumor cells in medium with a high salt concentration resulted in a partial inhibition of nuclear RNA synthesis. The residual RNA polymerase activity in such nuclei was only slightly inhibited by low concentrations (50 nM) of alpha-amanitin. This finding suggested an inhibition of RNA polymerase II activity under conditions of medium hypertonicity. Indeed, RNA polymerase II, isolated from the nuclei of cells exposed to hypertonicity, revealed only half of the control activity. On the other hand, RNA polymerase I was not affected by hypertonicity. Moreover, chromatin fractions isolated from cells incubated in hypertonic or isotonic medium were equally template-active in RNA synthesis.     

Inhibitory effect of flavonoids on DNA-dependent DNA and RNA polymerases

Flavonoids, (-)-epigallocatechin (1), myricetin (2) and quercetin (3), were investigated for inhibitory effects on E. coli DNA polymerase I and T7 bacteriophage RNA polymerase. In both DNA and RNA synthesis, 1 and 3 inhibited enzyme reactions by non-competitive and mixed type inhibition respectively, with regard to template DNAs. Myricetin (2) inhibited DNA and RNA polymerase reactions by mixed type and competitive type inhibition, respectively, with template DNAs. It was suggested that 2 interacts with covalently closed circular DNA.     

High salt effect on RNA synthesis in Krebs ascites tumor cells

Summary The incubation of Krebs ascites tumor cells in medium with a high salt concentration resulted in a partial inhibition of nuclear RNA synthesis. The residual RNA polymerase activity in such nuclei was only slightly inhibited by low concentrations (50 nM) of -amanitin. This finding suggested an inhibition of RNA polymerase II activity under conditions of medium hypertonicity. Indeed, RNA polymerase II, isolated from the nuclei of cells exposed to hypertonicity, revealed only half of the control activity. On the other hand, RNA polymerase I was not affected by hypertonicity. Moreover, chromatin fractions isolated from cells incubated in hypertonic or isotonic medium were equally template-active in RNA synthesis.This investigation was supported by the Turkish Scientific and Technical Research Council (TÜBITAK), Project No. TAG 339.     

Kelletinin I and kelletinin A from the marine mollusc Buccinulum corneum are inhibitors of eukaryotic DNA polymerase alpha

The inhibitory effect of esters of p-hydroxybenzoic acid (kelletinins I and A), extracted from the marine gastropod Buccinulum corneum, have been tested on eukaryotic and prokaryotic enzymes of DNA metabolism such as DNA polymerases alpha and beta, DNA polymerase I, Exo III, pancreatic DNAse I, micrococcal DNAse and E. coli RNA polymerase. Kelletinin I and kelletinin A inhibit preferentially DNA polymerase alpha. The inhibitory effect of kelletinin I involves the hydroxyl group of p-hydroxybenzoic acid.     

Zur Wirkung von Zn++ auf die Nukleinsäurebiosynthese von Aszites-Tumorzellen

Summary Ascites tumour cells have been employed to study the reactivity of Zn⁺⁺ on nucleic acid biosynthesis. 10^–4 M Zn⁺⁺ caused a selective inhibition of DNA synthesis of intact cells. The rate of RNA- and protein-biosynthesis, however, remained unchanged. The activity of DNA polymerase as well as DNA dependent RNA polymerase was strongly affected by Zn⁺⁺ in vitro.