Nucleotide excision repair, a tracking mechanism in search of damage.

Nucleotide excision repair (NER)l in all organisms, is able to accommodate to virtually any kind of DNA damage unlike many repair systems whose specificity is limited to a single species of damage. As a consequence NER has the advantage of being effective in responding to new types of environmental agents able to damage DNA. The model repair system under extensive study is the Escherichia coli uvr system consisting of at least 6 structural genes (uurA, uvrB, uvrC, uurD, polA, and lig) and 2 regulatory genes (recA and EexA) that control excision repair; these have been cloned, mapped, and sequenced and their gene products amplified and purified to homogeneity Cyeung et al., 1983,1986a, 1986b; Sancar and Sancar, 1988; Van Houten, 1990). The availability of reagent quantities of these proteins has been instrumental in the biochemical reconstitution of the partial and overall NER enzymatic reactions.