#Id: 6136
#Unit 3. Fundamental Processes
XPC detect distortions = UvrA in E. coli
Formation of the bubble involves the helicase activities of the proteins XPA and XPD (the equivalent to UvrB in E. coli) and the single-strand-binding protein RPA. The bubble creates cleavage sites 5’ to the lesion for a nuclease known as ERCC1-XPF and 3’ to the lesion for nuclease XPG (representing the function of UvrC). In higher cells, the resulting DNA strand is 24–32 nucleotides long. As in bacteria, the DNA strand is released to create a gap that is filled in by the action of DNA polymerase and ligase.
XPB and XPD are both helicases; the XPB helicase is required for promoter melting during transcription, while the XPD helicase performs the unwinding function in NER
