The involvement of polynucleotide ligase in the repair of UV-induced DNA damage in Escherichia coli K-12 cells.

The effect of the ligts-7 mutation on cell survival and the extent of DNA repair after UV (254 nm) irradiation was determined for wild-type and uvrB5 cells of E. coli K-12 at 30 degrees and 42 degrees C. At the restrictive temperature (42 degrees C) the ligts-7 mutation resulted in (i) a decrease in the extent of repair of DNA incision breaks arising during the excision repair process, and (ii) a decrease in the extent of post-replicational repair of gaps in newly-synthesized DNA. These deficiencies in DNA repair correlated with increases in cellular sensitivity to killing by UV radiation. Thus, DNA lagase plays an important role in vivo in both the excision and post-replicational repair processes.