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J Virol. 1973 July; 12(1): 1-8
Copyright © 1973 American Society for Microbiology. All Rights Reserved.

Injection of Ultraviolet-Damage-Specific Enzyme by T4 Bacteriophage

¹ Department of Human Genetics, University of Pennsylvania, Philadelphia, Pennsylvania 19104

ABSTRACT

When UV-irradiated T4 bacteriophage (v⁺) infects in the presence of chloramphenicol, the phage DNA rapidly acquires single-stranded breaks proportional to the dose of UV. In contrast, when UV-irradiated T4 v₁ (radiation sensitive mutant) infects under identical conditions, the phage DNA remains integral. A series of coinfections with v⁺ and v₁ phage (UV-v₁ + majority non-UV-v⁺ and UV-v⁺ and majority non-UV-v₁) show that the enzyme responsible for breakage is injected by the phage. It is also demonstrated that the v₁ phage injects an inactive enzyme that delays breakage by the v⁺ enzyme and interferes with subsequent repair. The cross of v⁺ and v₁ phage produces mixed progeny that contain both active and inactive enzyme in a single capsid. The possible function of this breaking enzyme, necessitating injection of multiple copies, is considered.