Effect of ultraviolet irradiation of bacteriophage f1 DNA on its conversion to replicative form by extracts of Escherichia coli.

When DNA of phage chiX174 or phage f1 is used as a template after exposure to ultraviolet radiation, the conversion of single-stranded DNA to replicative form by cell-free extracts of Escherichia coli is inhibited. The extend of synthesis is proportional to the distance of a pyrimidine dimer from a specific origin of replication as calculated from the random location of dimers at various UV doses. The results therefore indicate that the initiation of DNA synthesis on these phage DNAs occurs normally at a specific site, and that chain elongation is blocked when replication reaches a photo product in the template. Reinitiation of DNA synthesis distal to the lesion does not occur.