Overproduction Of RNA Research Articles

Effect of altered efficiency of the RNA I and RNA II promoters on in vivo replication of ColE1-like plasmids in Escherichia coli.

Thermal inactivation of the dnaA gene product leads to a considerable decrease in the rate of replication of ColE1-like plasmids. To test the possibility that the dnaA protein may affect synthesis of RNA I, which is an inhibitor of primer formation, or synthesis of RNA II, which is the primer precursor for replication of ColE1 ( Tomizawa and Itoh 1982), the effect of the dnaA46 mutation on the efficiency of the RNA I and the RNA II promoters was examined. It appears that thermal inactivation of the dnaA protein results in a considerable increase in the activity of the RNA I promoter. We suggest that overproduction of RNA I in dnaA mutants grown at the restrictive temperature is responsible for the reduced replication of ColE1-like plasmids. It has been found that addition of rifampicin to cultures of the dnaA46 or the dna+ strain grown at 42 degrees C results in a dramatic increase in the rate of replication of ColE1-like plasmids. We show that the activity of the RNA II promoter at 42 degrees C is exceptionally resistant to rifampicin. In the presence of the drug, this leads, to an altered ratio of RNA I to RNA II, in favor of the latter RNA species.

Autonomous Replication and Expression of RNA 1 from Black Beetle Virus

Black beetle virions contain two RNAs. The smaller one, RNA 2, has previously been shown to be a messenger for viral coat protein. It is shown here, by infecting sensitized Drosophila cells with the individually purified RNAs, that the larger one, RNA 1, carries the viral gene(s) required for RNA polymerase functions. RNA 2 was dispensible for synthesis of viral RNA 1 and subgenomic RNA 3 but was essential for synthesis of RNA 2 and virions. Cells infected with RNA 1 alone produced RNA 3 in proportions 10- to 20-fold greater than cells infected with virions. This overproduction of RNA 3 decreased with increasing proportions of RNA 2 in the infecting RNA 1. We conclude that RNA 1 is the previously unidentified progenitor of subgenomic RNA 3, whereas RNA 2 regulates the amount of RNA 3 produced in the infected cell.

The effect of 5-methyltryptophan on the synthesis of protein and RNA by Escherichia coli

1. 5-Methyltryptophan inhibits the synthesis of protein by Escherichia coli. In “stringent” but not in “relaxed” strains there is a similar reduction in the rate of synthesis of RNA. This difference is discussed in relation to current ideas concerning the regulation of RNA synthesis. 2. Ribosomes and neosomes (the immediate precursors of ribosomes) are synthesized by both stringent and relaxed strains in the presence of the amino acid analogue. 3. In addition, relaxed organisms accumulate particles sedimenting at about 15 S, a phenomenon that is characteristic of situations in which considerable differential synthesis of RNA occurs. 4. The overproduction of RNA in a relaxed strain is accompanied by preferential synthesis of ribosomal protein. 5. RNA derived from the 15-S particles accumulated by the relaxed strain in the presence of 5-methyltryptophan differs slightly from RNA isolated from ribosomes.