Influence of T4 on the formation of RNA phage-specific polyribosomes and polymerase

Effect of bacteriophage ghost infection on protein synthesis in Escherichia coli

The rate of protein synthesis by Escherichia coli markedly decreased within 1 min after phage T4 infection, whereas a complete cessation of protein synthesis was observed within at least 25 sec after T4 ghost infection. The cellular level of amino acids and aminoacyl-transfer ribonucleic acid (tRNA) did not change drastically upon infection with ghosts, indicating that the inhibition of protein synthesis took place at a step(s) beyond aminoacyl-tRNA formation. The host messenger RNA remained intact and still bound to ribosomes shortly after ghost infection. Kinetic studies of the effect of ghosts on host protein synthesis revealed that nascent peptide chains on ribosomes were not released upon ghost infection.

Inhibition of replication of ribonucleic acid bacteriophage f2 by superinfection with bacteriophage T4

Superinfection by phage T4 of cells infected by the ribonucleic acid (RNA) phage f2 results in inhibition of further f2 production. Experiments using rifampin show that the exclusion of f2 requires T4 gene function soon after T4 infection. By using a sensitive new peptide-mapping procedure to identify f2 coat protein in infected cells, we show that synthesis of the f2 coat occurs at a reduced level until 4 min after T4 superinfection and then ceases abruptly. Within 4 min after T4 superinfection, there are also several changes in f2 RNA metabolism, all of which require T4 gene function: preexisting f2 replicative intermediate RNA and f2 single-stranded RNA are degraded to small but still acid-precipitable fragments, and most f2-specific RNA is released from polyribosomes. We favor the hypothesis that T4 induces the synthesis of a specific endoribonuclease which degrades f2 RNA and that the inhibition of f2 protein synthesis may be a consequence of this degradation, rather than a direct effect of T4 upon translation.

System of double infection between vaccinia virus and mengovirus

When L cells are simultaneously infected with vaccinia virus and mengovirus, double interference in the replication of both viruses is observed. Superinfection of vaccinia virus-infected cells by mengovirus during the first 5 hr of infection reduces vaccinia virus yields to between 1 and 3% of controls. The yields of mengovirus are reduced to between 1 and 16% of controls, depending upon the time of superinfection. The replication of vaccinia deoxyribonucleic acid is not inhibited by mengovirus; it is only delayed. On the other hand, vaccinia multiplication severely hinders the replication of mengovirus ribonucleic acid. The double-infected system, at early times, synthesizes proteins that resemble those synthesized in the vaccinia virus-infected cells. Later in infection, however, the pattern is switched to proteins synthesized by mengovirus-infected cells. Possible mechanisms for this double interference in multiplication are discussed.

Inhibition of host protein synthesis during infection of Escherichia coli by bacteriophage T4. II. Induction of host messenger ribonucleic acid and its exclusion from polysomes

Two gene clusters on the Escherichia coli chromosome were induced at early times after T4 infection when >99% of the cells were infected: the lactose (lac) operon and prophage lambda. Their messenger ribonucleic acid (mRNA) was detected by hybridization to phi80 dlac deoxyribonucleic acid (DNA) and lambdaDNA, respectively. Synthesis of host mRNA could be initiated during the first few minutes after T4 infection, although no beta-galactosidase activity could be detected. Hybridization analyses of selected fractions from sucrose gradients revealed that most of this lac mRNA induced at very early times of T4 infection was not associated with ribosomes. In contrast, virtually all lac mRNA in uninfected bacteria was associated with polysomes. This exclusion affected all host mRNA; about 70% of E. coli(3)H-mRNA, labeled from 2 to 3 min after T4 infection, was excluded from polysomes. Infection even reduced the yield of beta-galactosidase from lac mRNA induced before infection. Gradients from rifampicin-inhibited cells showed the normal growth of lac mRNA polysomes; in contrast, T4 infection prevented growth of the preinduced lac polysomes. It is concluded that T4 infection interferes within seconds with the reassociation of ribosomes to host mRNA.

Leucine tRNA and cessation of Escherichia coli protein synthesis upon phage T2 infection

The involvement of tRNA in cellular differentiation has been tested by analyzing aminoacyl-tRNA of Escherichia coli after phage T2 infection. One or two minutes after infection, half of one of the five leucine tRNA components (Leu-tRNA(1), CUG responding) undergoes a drastic structural change which leads to inactivity of both leucine acceptor activity and codon response. Whether or not the modification causes cessation of host protein synthesis without inhibiting phage-specific protein synthesis has been examined by analyzing polysome-bound leucine tRNA of E. coli before and after the phage infection. The results presented in this paper indicate that the amount of Leu-tRNA(1) used after infection was greatly reduced as compared to that used in noninfected cells. Studies of the in vitro protein-synthesizing system show that T2 mRNA rarely contains the CUG codon. A mechanism by which host mRNA translation is inhibited by the phage infection is proposed from this available information.