Project: XPF-ERCC1 heterodimer is the endonuclease responsible for the 5' incision in nucleotide excision repair. I am interested in the details of this endonuclease, specifically the helix-hairpin-helix (HeH2) domain in both subunits, XPF and ERCC1. Based on recent structural studies, I will apply site-directed mutagenesis to mutate several proposed key residues important for the DNA binding activity.