The effects of neopluramycin and bleomycins A
2 and A
6, functioning as antibiotics by binding to DNA, on the transcription of T4 phage were studied. Neopluramycin was observed to inhibit both
in vivo and
in vitro transcription of T4 phage. It also interfered with the development of infectious phage particles. Although bleomycins A
2 and A
5 did not significantly affect
in vivo transcription of T4 phage, they inhibited the
in vitro transcription, when the template phage DNA was incubated with the antibiotics for 10 minutes prior to the addition of RNA polymerase and nucleoside triphosphates. The RNAs synthesized in the presence of the antibiotics were smaller and seemed to contain larger ratio of pre-early RNA than the RNA synthesized in the absence of antibiotics. The results were in accordance with the assumption that the antibiotics inhibit RNA synthesis by binding to the template DNA and interfering with the elongation step of the RNA polymerase reaction. The RNA polymerase reaction, using calf thymus DNA as a template, was also inhibited by the antibiotics.
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