[Postreplication DNA repair in Escherichia coli cells. I. Defect of inducible repair in the thermosensitive mutant AX727 dnaZts at a nonpermissive temperature].

After UV-irradiation at the non-permissive temperature 43 degrees C the survival of the thermosensitive mutant Escherichia coli AX727 dnaZts (the dnaZ gene controls the synthesis of gamma-subunit of DNA polymerase III holoenzyme) appeared somewhat lower and postreplication perair of its DNA less effective by 5-15% than at the permissive temperature 30 degrees. The survival of chloramphenicol treated cells decreased both at 43 and 30 degrees C. Under the influence of chloramphenicol, the postreplication repair of DNA in AX727 dnaZts cells at 30 degrees lower to the level of this process seen at 43 degrees C. The same process in thermoresistant revertant AX729 dnaZtr at 30 degrees and 43 degrees C decreased to the level of the process in AX727 cells at 43 degrees C. The data indicate that dnaZ gene product is necessary for the inducible branch of postreplication DNA repair. By this process (presumably together with prereplication excision repair), the cell eliminates 20% of UV-inducible lethal damages. Besides, in AX727 dnaZts cells there functions protein synthesis dependent repair not associated with the postreplication repair of DNA; this latter process eliminates about 60% lethal damages of the cell.