Selective gene transcription in bacteriophage T4 by putrescine

Polyamine stimulation of nucleic acid synthesis in an uninfected and phage-infected polyamine auxotroph of Escherichia coli K12 (arginine-agmatine ureohydrolase-putrescine-spermidine-lysine-cadaverine)

The addition of arginine to cultures of Escherichia coli K12 deficient in agmatine ureohydrolase (EC 3.5.3.7) results in polyamine depletion and a striking inhibition of nucleic acid accumulation and growth. The omission of lysine from these cultures leads to a further decrease in growth rate and nucleic acid synthesis. In arginine-inhibited cells the addition of putrescine or spermidine, in the presence or absence of lysine, restores the control rate of growth and nucleic acid accumulation. Under the same conditions of arginine inhibition in the absence of lysine, the addition of cadeverine alone stimulates growth rate and RNA synthesis. The addition of lysine to polyamine-depleted cultures results in cadaverine production and in the appearance of a new spermidine analogue, containing lysine carbon. The new compound has been identified as N-3-aminopropyl-1,5-diaminopentane. Infection of this arginine-inhibited, polyamine-depleted mutant with T(4)D results in markedly decreased amounts of DNA accumulation, as compared to infected cells uninhibited by arginine. Supplementation of arginine-inhibited infected cells by putrescine or spermidine restores DNA synthesis to the uninhibited level.

Conversion of T4 gene 46 mutant deoxyribonucleic acid into nonviable bacteriophage particles

The T4 amber mutant N130 in gene 46 produces, upon infection of a nonpermissive host, about 10 times more phage equivalent of deoxyribonucleic acid (DNA) than viable phage particles. Intracellular DNA is shorter than its mature phage counterpart and is converted into nonviable, light phage particles (287S) with about half of the normal DNA content, incapable either of adsorbing to or killing host bacteria. This DNA is highly unstable and breaks down, upon extraction, into subunits one-tenth the normal length of T4 DNA. Electron micrographs showed that the nonviable particles consist of normal-sized capsids of various degrees of fullness. Abnormal tail structures (naked cores with the sheaths missing) were also observed. Under conditions of arrested DNA synthesis, late messenger ribonucleic acid is produced, but some species are rare or missing, resulting in uneven transcription of the late genes. Our findings indicate that continuous DNA replication is necessary for normal transcription in T4.

Differential effect of polyamines on T4 morphogenesis

The 5-fluorouracil (5 FU) technique for the phenotypic reversion of amber mutants was used to demonstrate that under certain circumstances, in the presence of putrescine or spermidine, early mutants have an enhanced response to 5 FU, whereas late mutants have a delayed response. Bacteria infected by T4D wild-type bacteriophage did not produce phage in the presence of high putrescine concentrations. Pulse treatments with putrescine showed that the production of lysozyme depends on a putrescine-sensitive process that begins immediately after infection at 26 C and ends at 36 min or even later. The addition of putrescine at any time during the critical period between 0 and 36 min led to a corresponding delay in lysozyme synthesis after the inhibitor was removed. Intracellular phage maturation was delayed by the addition of 100 mumoles of putrescine per ml. Early enzymes were not affected by the diamine, but the level of phage deoxyribonucleic acid was considerably decreased by the inhibitor. The putrescine-sensitive process that affects the timing of maturation is suggested to be the natural process controlling the T4 "clock."