Architecture of nucleotide excision repair complexes: DNA is wrapped by UvrB before and after damage recognition

Nucleotide excision repair (NER) is a major DNA repair mechanism that recog nizes a broad range of DNA damages. In Escherichia coli, damage recognition in NER is accomplished by the UvrA and UvrB proteins, We have analysed the structural properties of the different protein-DNA complexes formed by Uvr A, UvrB and (damaged) DNA using atomic force microscopy. Analysis of the Uv rA(2)B complex in search of damage revealed the DNA to be wrapped around th e UvrB protein, comprising a region of about seven helical turns. In the UV rB-DNA pre-incision complex the DNA is wrapped in a similar way and this DN A configuration is dependent on ATP binding. Based on these results, a role for DNA wrapping in damage recognition is proposed. Evidence is presented that DNA wrapping in the pre-incision complex also stimulates the rate of i ncision by UvrC.