Effects of -amanitin on in vitro labeling of RNA from defined nuclear components in salivary gland cells from Chironomus tentans

The effect of alpha-amanitin on nucleoside labeling of RNA in nucleoli, chromosomes, nuclear sap, and cytoplasm from Chironomus tentans salivary gland cells was investigated by radioautography and gel electrophoresis. Preribosomal RNA formation and processing in the nucleolus was not measurably influenced by the drug, and both 28 S and 18 S ribosomal RNA were transferred to the cytoplasm. In the chromosomes the heterogeneous RNA labeling was completely inhibited for the large size range (above 45-50 S) and partially for the low range. The labeling of 4-5 S chromosomal RNA was only moderately reduced. Most of the chromosomes showed radioautographically a disappearance of the normal band pattern, but some retained a pattern of weakly labeled bands. The electrophoretic results for the nuclear sap paralleled those for the chromosomes. The effect of alpha-amanitin on RNA labeling in these cells is similar but not identical to that of the substituted benzimidazole 5,6-dichloro-1(beta-D-ribofuranosyl) benzimidazole (DRB).

Transcription of the adenovirus genome by an -amanitine-sensitive ribonucleic acid polymerase in HeLa cells

The properties of the ribonucleic acid (RNA) polymerase activity which transcribes the major portion of the adenovirus genome were studied. Nuclei were prepared from infected cells and incubated in vitro. Virus-specific RNA was determined by hybridization to adenovirus deoxyribonucleic acid (DNA). Adenovirus DNA is transcribed principally by an activity which resembles closely polymerase II of the host cell. This activity is inhibited by alpha-amanitine and stimulated by (NH(4))(2)SO(4). Its product is high-molecular-weight heterogeneous RNA. The polymerase activity measured early in infection (3 to 5 hr) resembles that found late in infection (16 to 18 hr).

Studies on isolated brain nuclear DNA-dependent RNA polymerase

DNA-dependent RNA polymerase, which was isolated from beef brain nuclei, was stimulated by Mn2+ and Mg2+. The polymerase was about four times as active with Mn2+ as with Mg2+ but both of these divalent cations were required for maximum activity. KCl stimulated the enzyme activity with an optimum concentration around 0.2 M. The stimulation by KCl was much more pronounced in the presence of Mn2+ or Mn2+ plus Mg24 than in the presence of Mg2+ alone. Spermidine and spermine also stimulated the RNA polymerase activity and this stimulation was much greater in the presence of Mn2+ than in the presence of Mg2+ or both together. With Mn2+ plus Mg2+, spermidine had little or no stimulatory effect when heat-denatured DNA served as template, whereas with Mn2+ alone, spermidine markedly stimulated the enzyme in the presence of either native or heat-denatured DNA. The effect of spermidine was different with Mg2+ alone. The enzyme was inhibited as much as 75% by actinomycin D and almost completely by α-amanitin but not by rifampicin. Yeast RNA inhibited the enzyme activity considerably while spermidine appeared to overcome and prevent this inhibition of RNA polymerase.

Rifamycin-resistant mutation in E. coli: effect of rifamycin on DNA-dependent RNA polymerase and on R17 phage growth

Rifamycin-resistant mutants in E. coli, K12, Hfr strain, were isolated without mutagenic treatment. The frequency of natural mutation of this type appeared to be approximately 10−9. Selection of resistant strains was effected by plating 109 cells on agar plates containing 50 μg of rifamycin per milliliter. A total of 11 strains resistant to rifamycin thus isolated remained Hfr and, in the presence of rifamycin, permitted the growth of the RNA-containing, male specific coliphage R17, which is sensitive to rifamycin in a wild-type E. coli. DNA-dependent RNA polymerase was prepared from these resistant mutants and examined for sensitivity toward rifamycin and other antibiotics. It was found that the RNA polymerase of the resistant strain is indeed resistant to rifamycin. However, both rifamycin-resistant and -sensitive enzymes are inhibited by the other three antibiotics (acridine orange, ethidium bromide, actinomycin D), which are known to interact with the template molecule.

DNA-dependent RNA polymerase from Tetrahymena pyriformis

DNA-dependent RNA polymerase has been isolated from sonicated nuclei of the ciliate protozoan Tetrahymena pyriformis. The enzyme has been further purified by column chromatography on DEAE-Sephadex and is approximately 300-fold purified relative to total cellular protein.