Suppression of a mutation in gene 3 of bacteriophage T7 (T7 endonuclease I) by mutations in phage and host polynucleotide ligase.

Bacteriophage T7 bearing amber mutations in both gene 1.3 (T7 DNA ligase) and gene 3 (T7 endonuclease I) are viable when grown in suppressor-negative, ligase-negative hosts. This is evidenced by a high plating efficiency and a large burst size compared to the single mutants. These findings may be explained by a limited destruction of cellular DNA by the double mutant.