Abstract
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.
Highlights
UvrA must be able to recognize a single damaged site per E. coli genome
RNA transcription-dependent supercoiling requires the specific binding of RNA polymerase (RNAP) to its promoter for translocation along a transcription unit, whereas SV40 T antigen and the UvrAB complex can bind to DNA nonspecifically
The findings presented suggest that RNAP enhances UvrAB supercoiling as a consequence of the specific binding of RNAP to its promoter
Summary
In Escherichia coli, NER1 requires an ensemble of gene prod- place the stalled RNAP complex and to lead the UvrABC comucts including the UvrABC endonuclease to incise plex to the site of the lesion possibly due to its affinity for the DNA on both sides of a damaged nucleotide [1,2,3,4]. These characteristics suggest that the UvrAB complex From reversible cross-linking experiments and resolution of tracks along DNA scanning for damage in an ATP hydrolysis-de- the resultant components of E. coli RNAP with the Uvr propendent manner [13, 14] and that the helix-turn-helix [15] and teins during SOS, it is suggested that a physical interaction polyhinge regions [16] of UvrA are required for damage recogni- between RNAP and repair proteins may be required for the tion.
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