Breakage of polynucleotide strands by disintegration of radiophosphorus atoms in DNA molecules and their repair: I. Single-strand breakage by transmutation

Abstract

It was previously shown in vitro that a single disintegration of a 32P atom incorporated in a molecule of species I (covalently closed double-circular molecule) of λ DNA causes a structural change of the molecule by breakage of one or both of the polynucleotide strands (H. Ogawa & Tomizawa, 1967). Similar changes in molecules of species I take place, in vivo, when cells carrying the molecules derived from 32P-labelled λ phage are stored at −79 °C. When the cells carrying the molecules with strand interruption were incubated at 37 °C, many of the interruptions were repaired. The reaction is quite extensive and rapid, so that 80% of the interruptions were repaired in several minutes. The function(s) necessary for the repair is provided by the host bacteria. A recombination-deficient mutant and some ultraviolet light-sensitive mutants are found to have similar ability to repair single-strand breaks.