Fig. 1. Nucleotide excision repair in Escherichia coli.

Damage detection in nucleotide excision repair in E. coli proceeds via global damage surveillance executed by UvrA₂(B), and RNA polymerase (RNAP) transcribing damaged template DNA. The UvrA dimer loads UvrB, which verifies the presence of DNA damage in a strand-specific manner. Alternately, stalled elongation complexes at the site of DNA damage are rescued by the transcription-repair coupling factor Mfd, which in turn recruits UvrA₂(B) to the site of the stalled RNAP. This is followed by strand-specific loading of UvrB at the site of the lesion. Following damage verification by UvrB, a single-stranded patch of DNA containing the damage is incised by the UvrC endonuclease. This is followed by repair synthesis and ligation coordinated by UvrD, PolI and LigA.