Nucleotide excision repair
Nucleotide excision repair is a type of DNA repair that mends pyrimidine dimers in DNA. In this repair pathway, an oligonucleotide containing the lesion is excised from the DNA and the resulting single-strand gap is filled in. This helps living things to prevent potentially harmful mutations from occurring.
In E. coli, pyrimidine dimers are recognized by a multisubunit enzyme, the product of the uvrA, uvrB, and uvrC genes. This UvrABC endonuclease, is an ATP-dependent reaction, cleaves the dimer-contain DNA strand at the seventh and fourth phosphodiester bonds on the dimer's 5' and 3' sides, respectively. The excised oligonucleotide is replaced through the action of a DNA polymerase, most probably Pol I, followed by that of DNA ligase.