An inhibitory protein of Escherichia coli RNA polymerase in bacteriophage T3-infected cells (core polymerase-sigma factor-host polymerase-phage polymerase-initiation)

A partially purified protein isolated from bacteriophage T3-infected cells of Escherichia coli B markedly inhibits the activity of E. coli RNA polymerase, slightly inhibits the activity of purified T3 polymerase, and does not inhibit the activity of either core polymerase or the ribosome-bound T3 polymerase. The properties of this protein and its mechanism of action have been studied. It appears to antagonize the action of the sigma factor component of RNA polymerase.

Nucleolar necklaces in chick embryo myoblasts formed by lack of arginine

The round nucleoli of chick embryo myoblasts, when grown in a culture medium devoid of arginine, unravel in several days into 5-20 micro long, beaded strands termed nucleolar necklaces (NN). Addition of arginine reverses this change. The NN contain protein, RNA, and traces of DNA as determined cytochemically by enzyme digestion and by acridine-orange fluorescent staining. When a cell containing the beaded strand is treated with agents, such as actinomycin D, that prevent rRNA polymerase action, the strand collapses and condenses into a small dense nucleolus with segregated regions of ribonucleoprotein (RNP) and deoxyribonucleoprotein (DNP). The properties of the NN appear to resemble those of the nucleolar necklaces of amphibian oocytes. Cycloheximide or puromycin inhibition of general protein synthesis does not lead to NN formation. We suggest that NN formation during arginine starvation may be a result of a singular depletion of some rapidly turning over, arginine-rich proteins that normally attach to ribosomal RNA precursor molecules during their synthesis in the processing towards maturation of the ribosomes.

Effect of alpha-amanitin on ribonucleic acid polymerase II of rat brain nuclei and on retention of avoidance conditioning

1. alpha-Amanitin inhibits in vitro the activity of RNA polymerase II of rat brain nuclei. 2. The toxin does not pass the blood-brain barrier, but when injected intracerebrally is highly toxic for rats, and causes inhibition of RNA polymerase II of isolated brain nuclei. 3. Intracerebral injection of alpha-amanitin 6h before training to a passive avoidance task is followed by impaired performance of rats on retesting after 7 days, without affecting performance on retesting immediately after training.

Differential effects of -amanitin on RNA polymerase activity in nuclei and mitochondria

Concentrations of α-amanitin which strongly inhibit nuclear RNA polymerase activity in presence of Mn2+ and ammonium sulfate did not produce any significant inhibition of RNA polymerase activity in mitochondria from rat brain, spleen, liver, and kidney under identical conditions. Much higher concentrations of α-amanitin, however, inhibited the mitochondrial RNA polymerase. The effects of α-amanitin on the mitochondrial RNA polymerase activity in presence of Mg2+ were similar to those on nuclear enzyme under the same conditions; in both cases only relatively very high concentrations produced significant inhibition.

Specific interaction of tRNA 3'-terminal nucleotidyl transferase with polynucleates

E. coli tRNA lacking one or more of the 3′-terminal bases was prepared for use in the tRNA 3′-terminal nucleotidyl transferase system, by periodate–amine cleavage or by snake venom phosphodiesterase treatment. Optimal conditions for the transferase reaction with tRNA-pC and tRNA-pCpC and for detection of complexing of various nucleic acids to transferase were determined.Although R17 RNA-pC, R17 RNA-pCpC, and synthetic polynucleotides are unable to accept nucleoside monophosphates in the enzymic reaction, it was found that they are able to form complexes with the enzyme. The extent of binding depends inversely on the degree of base stacking in the synthetic polynucleotide. In keeping with this, melting of tRNA reduces both the CMP-accepting activity and the binding capacity. In competition studies, it was found that R17 RNA and tRNA compete with one another for binding, and that R17 RNA and to lesser extents, poly-U and poly-A, inhibit the transferase reaction with tRNA. Thermal studies, however, show that only tRNA can protect the enzyme from heat inactivation. These findings suggest that the recognition process for transferase and its nucleic acid substrate involves at least a two-step interaction. First, there is nonspecific binding which is followed by specific complex formation, an event which depends on the specific structure of tRNA.

RNA polymerases of maize: nuclear RNA polymerases

Two DNA-dependent RNA polymerases of nuclear origin have been purified from leaves of Zea mays. The two enzymes can be separated on DEAE-cellulose columns. Enzymes I and II are eluted with 0.08 and 0.20 M (NH(4))(2)SO(4), respectively. Both enzymes prefer maize nuclear DNA as a template; they are also more active in the presence of Mg(++) than Mn(++) and are inhibited by (NH(4))(2)-SO(4) or KCl. Neither enzyme is inhibited by rifamycin SV. Enzyme II is strongly inhibited by alpha-amanitin, whereas enzyme I is not significantly affected. Their ability to use native and denatured DNA as templates varies according to the extent and method of purification of the polymerase. Furthermore, enzyme II can be resolved by DEAE-chromatography or glycerol-gradient centrifugation into two components, one of which prefers native DNA, while the other prefers denatured DNA.

Chemosterilant action of anthramycin: a proposed mechanism

The activity of anthramycin and structurally related analogs as chemosterilants of the housefly, Musca domestica L., correlates closely with the action of these compounds as inhibitors of Escherichia coli RNA polymerase. Since inhibition of RNA polymerase by anthramycin reflects binding of this antibiotic to the DNA primer required for enzyme activity, we propose that the interaction of anthramycin with DNA may also account for its action as a chemosterilant.

Salicylate and enzymes

Salicylate inhibits the activities of a number of cellular enzymes and in some instances the mechanisms of inhibition have been established (Smith, 1968a). Reported inhibitory actions of the salicylate ion on important enzyme systems in vitro are now reviewed and assessed in relation to the known clinical and toxic effects of the drug.

RNA polymerases of maize: partial purification and properties of the chloroplast enzyme

A DNA-dependent RNA polymerase has been solubilized and partially purified from washed chloroplasts prepared from maize seedlings. The purified enzyme was completely dependent on added DNA after purification by phospho- or DEAE-cellulose chromatography. On glycerol density gradients, the enzyme ran ahead of a marker with a sedimentation constant of 18 S, indicating a molecular weight of 500,000 or more. The instability of the highly purified enzyme made intensive study difficult, but the properties of the enzyme purified by phosphocellulose chromatography are reported. Template specificity varied during purification but the activity was always higher with denatured than with native DNA and the preference for maize DNA over calf-thymus DNA increased during purification. The enzyme required magnesium for optimal activity, was inhibited by salt concentrations in excess of 0.1 M, and had a temperature optimum of 48 degrees C. The chloroplast enzyme differed from similar activities so far reported from maize or other sources, particularly in the high salt concentrations needed to elute it from phosphocellulose. The soluble, DNA-dependent enzyme was not inhibited by either alpha-amanitin or by rifamycin-SV under the assay conditions used.