RNA polymerase and the shut-off of host RNA and protein synthesis in T4 phage infection

Studies on deoxyribonucleic acid-dependent ribonucleic acid polymerase from Escherichia coli. Variations of the enzyme activity during growth

1. RNA polymerase activity of Escherichia coli extracts prepared from cells in exponential and stationary phases of growth, when measured in the presence and absence of external template, showed significant qualitative differences. 2. In both extracts, polymerase activity was higher when assayed with external template, suggesting the presence of a pool of enzyme not bound to cellular DNA. 3. In the crude extract, the fraction of enzyme bound to cellular DNA is higher during the exponential phase of growth. 4. A method is described for the purification of enzyme molecules not tightly bound to cellular DNA from exponential- and stationary-phase cultures. 5. Purified enzyme preparations showed differences in template requirement and subunit composition. 6. On phosphocellulose chromatography of stationary-phase enzyme, a major portion of polymerase activity eluted from the column with 0.25m-KCl. In the case of exponential-phase enzyme, polymerase activity eluted from a phosphocellulose column mainly with 0.35m-KCl. 7. Enzyme assays done with excess of bacteriophage T(4) DNA showed a strong inhibition of stationary-phase enzyme by this template. The exponential-phase enzyme was only slightly inhibited by excess of bacteriophage T(4) DNA.

Inhibition of host protein synthesis during infection of Escherichi coli by bacteriophage T4. 3. Inhibition by ghosts

Deoxyribonucleic acid (DNA)-less T2 "ghosts" were prepared by osmotic shock and purified by KBr density gradient centrifugation. Escherichia coli B was treated with these ghosts in inorganic salts-glycerol medium to see which features of phage infection could be elicited by ghosts. At a multiplicity that was just sufficient to block induction of beta-galactosidase (EC 3.2.1.23), 89% of the bacteria were killed and the rates of ribonucleic acid (RNA) and DNA synthesis were about 10 to 15% of normal. However, protein synthesis was almost completely blocked but resumed after 30 min. During this period, it was possible to induce messenger RNA (mRNA) from the lactose operon, although this mRNA could not be translated into active beta-galactosidase. These results suggest to us that the viable cells surviving ghost infection synthesize nucleic acids at close to a normal rate but are temporarily blocked in protein synthesis. The continued formation of untranslated host mRNA mimics the pattern of bacterial synthesis just after whole-phage infection, and is consistent with the interpretation that the immediate block in the initiation of host translation by these viruses is due to their attachment.

Nucleic acid synthesis in Bacillus subtilis infected with bacteriophage beta-22

Changes in the synthesis of host and phage nucleic acid after infection of Bacillus subtilis with virulent bacteriophage beta22 were analyzed by deoxyribonucleic acid (DNA)-DNA and ribonucleic acid (RNA)-DNA hybridization. Host DNA replication continued during the first third of the 55-min latent period and then ceased at approximately the time replication of the phage genome was initiated. Host-specific RNA was synthesized concurrently with phage RNA during the first half of the latent period but was repressed late in the infection. For much of the latent period, the population of phage-specific RNA changed continually as new species were transcribed and earlier species were repressed; detectable changes ceased coincidentally with the appearance of intracellular phage. Control over transcription of phage DNA was to some degree an intrinsic property of the interaction of B. subtilis DNA-dependent RNA polymerase and the phage genome, since only the early species of phage RNA were synthesized in vitro by B. subtilis polymerase and pure beta22 DNA. In vitro transcription of late functions was demonstrated by using the endogenous RNA polymerase activity of the nucleoprotein complex (nuclear fraction) from infected cells.