Synthesis of thymine and alpha-putrescinylthymine in bacteriophage phi W-14-infected Pseudomonas acidovorans

Abstract

Host DNA synthesis stopped about 10 min after the infection of Pseudomonas acidovorans with bacteriophage 4W-14, but host DNA was not degraded to acidsoluble fragments. The synthesis of host but not of phage DNA was inhibited by 5-fluorodeoxyuridine. The nucleotide pools of infected cells did not contain dTTP, and infection resulted in the appearance of dTTPase activity. Although ornithine labeled the a-putrescinylthymine residues of 4W-14 DNA, ornithine-labeled nucleotides were not detected in infected cells. A new deoxynucleoside triphosphate did appear in infected cells, but it was not labeled by ornithine. It is concluded that the thymine and a-putrescinylthymine in OW-14 DNA are synthesized at the polynucleotide level.

Polyamines in microorganisms.

“…The modification occurs at the polynucleotide level, with label from omithine appearing in the hypermodified base in vivo; in extracts, labeled putrescine is incorporated into the DNA. Studies with amber mutants indicate that a portion of the a-putrescinylthymine is essential for the production of viable phage, probably because of its effect on DNA packaging in the phage head (96,107,108,118,182).…”

Polypeptide synthesis directed by bacteriophage phi W-14 and by mutants defective in DNA synthesis

“…to acid-soluble fragments (9). Host-specific polypeptide synthesis ceases even later, after the initiation of synthesis of phage middle polypeptides.…”

Bacteriophage phi W-14-infected Pseudomonas acidovorans synthesizes hydroxymethyldeoxyuridine triphosphate

“…Neither thymine nor putThy is synthesized at the mononucleotide level in infected cells of Pseudomonas acidovorans because infection leads to the appearance of dTTPase activity and the cells do not contain dTTP or putThy nucleotides when phage DNA is made (11). A new pyrimidine deoxyribonucleoside triphosphate appears in the acid-soluble pool of infected cells (11). In this paper we show that this new nucleotide is 5hydroxymethyldeoxyuridine triphosphate (hmdUTP) and that newly replicated DNA contains hydroxymethyluracil (hmUra).…”

“…However, there is still detectable dTTP in the cells 10 to 15 min after infection when host DNA synthesis has stopped. This suggests that there may be a direct inhibition of host DNA polymerase after infection, since host DNA is not degraded to acid-soluble fragments (11). When phage DNA synthesis reaches its maximal rate some 30 min after infection (7), there is little dTTP left in the cells.…”