<p> The SOS response is required for efficient nucleotide excision repair (NER) of the major ultraviolet light (UV) induced DNA lesions. The expression of three NER genes, uvrA, uvrB, and uvrD, is upregulated as part of the SOS response. UvrD differs from the others in that it is not involved in lesion recognition but rather in promoting the post-incision steps of NER, including turnover of the UvrBC incision complex [<cite idref="PUB00007889"/>]. The form of the UvrD helicase with optimal helicase activity is oligomeric with at least two sites for binding the DNA substrate, where one site contacts regions of the 3'-ssDNA tail that are distal from the single-stranded/double-stranded DNA junction.</p> DNA helicase, ATP-dependent, UvrD type