title: Xeroderma pigmentosum complementation group A protein acts as a processivity factor.
abstract: We have previously shown that endonucleases present in a protein complex, which has specificity for cyclobutane pyrimidine dimers, locate sites of damage in DNA by a processive mechanism of action in normal human lymphoblastoid cells. In contrast, the endonucleases present in this complex from xeroderma pigmentosum complementation group A (XPA) cells locate damage sites by a distributive or significantly less processive mechanism. Since the XPA protein has been shown to be responsible for the DNA repair defect in XPA cells, this protein was examined for involvement in the mechanism of target site location of these endonucleases. A recombinant XPA protein, produced by expression of the normal XPA cDNA in E. coli, was isolated and purified. The results show that the recombinant XPA protein was able to correct the defect in ability of the XPA endonucleases to act by a processive mechanism of action on UVC irradiated DNA. These studies indicate that the XPA protein, in addition to a role in damage recognition or damage verification, may function as a processivity factor.
authors.affiliation: Department of Pathology, Laboratory Medicine, UMDNJ-New Jersey Medical School, 185 South Orange Avenue, Newark, New Jersey 07103, USA. mlambert@umdnj.edu
authors.forename: M W
authors.initials: MW
authors.lastname: Lambert
authors.forename: L
authors.initials: L
authors.lastname: Yang
mesh_terms: D002460:Cell Line; D004247:DNA / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004720:Endonucleases / Q000378:metabolism; D004926:Escherichia coli; D006801:Humans; D007700:Kinetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays; D014983:Xeroderma Pigmentosum / Q000201:enzymology / Q000378:metabolism*; D051760:Xeroderma Pigmentosum Group A Protein
chemical_list: D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; C497314:XPA protein, human; D051760:Xeroderma Pigmentosum Group A Protein; D004247:DNA; D004720:Endonucleases