Transcription when coupled to nucleotide excision repair specifies the location 
in active genes where preferential DNA repair is to take place. During DNA 
damage-induced recruitment of RNA polymerase (RNAP), there is a physical 
association of the beta subunit of Escherichia coli RNAP and the UvrA component 
of the repair apparatus (G. C. Lin and L. Grossman, submitted for publication). 
This molecular affinity is reflected in the ability of the RNAP to increase, in 
a promoter-dependent manner, DNA supercoiling by the UvrAB complex. In the 
presence of the RNAP, the UvrAB complex is able to bind to promoter regions and 
to translocate in a 5' to 3' direction along the non-transcribed strand. As a 
consequence of this helicase-catalyzed translocation, preferential incision of 
DNA damaged sites occurs downstream on the transcribed strand. Because of the 
helicase directionality, the initial binding of the UvrAB complex to the 
transcribed strand would inevitably lead to its collision with the RNAP. These 
results imply that the RNAP-induced DNA structure in the vicinity of the 
transcription start site signals a landing or entry site for the UvrAB complex 
on DNA.