A T4-Induced Endonuclease Which Attacks T4 DNA

A DNA endonucleolytic activity that introduces single-stranded breaks into native T4 DNA is found in T4-infected E. coli. This endonuclease attacks other double-stranded, but not single-stranded, DNA. Experiments with ultraviolet-irradiated phages and amber mutants indicate that the enzyme is made beginning about five minutes after infection at 37 degrees C.