title: Overexpression and purification of human XPA using a baculovirus expression system.
abstract: The xeroderma pigmentosum group A protein (XPA) is an essential component of the eukaryotic nucleotide excision repair (NER) process. Recombinant human XPA was expressed in baculovirus-infected insect cells as a [His](6)-tagged fusion protein. A two-column purification procedure resulted in greater than 90% purity for the recombinant protein with a final yield of 0.53 mg from 200 ml of infected cells. The recombinant protein migrated as a doublet of 44 and 42 kDa upon SDS-PAGE consistent with that observed for the native protein. XPA can interact with a number of proteins including replication protein A (RPA) which has been implicated in the initial recognition of damaged DNA. Using a modified ELISA, we demonstrate that the recombinant XPA fusion protein also forms a complex with RPA independent of DNA. The ability of XPA to bind damaged DNA was assessed in an electrophoretic mobility shift assay using globally cisplatin-damaged DNA. The results revealed a slight preference for DNA damaged with cisplatin consistent with its proposed role in the recognition of damaged DNA. The recombinant XPA fusion protein was able to complement cell-free extracts immunodepleted of XPA restoring NER-catalyzed incision of cisplatin-damaged DNA in an in vitro excision repair assay.
authors.affiliation: Department of Biochemistry and Molecular Biology, Wright State University School of Medicine, Dayton, Ohio 45435, USA.
authors.forename: I L
authors.initials: IL
authors.lastname: Hermanson
authors.forename: J J
authors.initials: JJ
authors.lastname: Turchi
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D002460:Cell Line; D002945:Cisplatin / Q000494:pharmacology; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005822:Genetic Vectors; D006367:HeLa Cells; D006801:Humans; D007313:Insecta / Q000166:cytology; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051716:Replication Protein A; D014983:Xeroderma Pigmentosum; D051760:Xeroderma Pigmentosum Group A Protein
chemical_list: D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; C497167:RPA1 protein, human; D011993:Recombinant Fusion Proteins; D051716:Replication Protein A; C497314:XPA protein, human; D051760:Xeroderma Pigmentosum Group A Protein; D004247:DNA; D002945:Cisplatin