title: Stable down-regulation of human polynucleotide kinase enhances spontaneous mutation frequency and sensitizes cells to genotoxic agents.
abstract: Human polynucleotide kinase (hPNK) is a 57.1-kDa monomeric protein with conserved motifs associated with phosphatase and kinase activities. hPNK catalyzes phosphorylation of 5'-DNA termini and dephosphorylation of 3'-DNA termini. Previous studies, employing cell-free systems, have suggested that hPNK participates in the repair of DNA strand breaks. To better define the cellular function of hPNK, a double-stranded small-interfering RNA molecule designed to stably target hPNK transcription was introduced into A549 human lung adenocarcinoma cells. The small-interfering RNA suppressed hPNK gene expression by at least 80-90%. These cells exhibited a 7-fold higher spontaneous mutation frequency based on the development of resistance to ouabain; elevated sensitivity to a broad range of genotoxic agents including gamma-radiation, UVC radiation, methyl methanesulfonate, hydrogen peroxide, and camptothecin; and slower repair of radiation-induced DNA strand breaks. These findings underscore the importance of hPNK in the maintenance of DNA integrity after damage induced by endogenous and exogenous agents.
authors.affiliation: Department of Experimental Oncology, Cross Cancer Institute, University of Alberta, Edmonton, AB, Canada T6G 1Z2.
authors.forename: Aghdass
authors.initials: A
authors.lastname: Rasouli-Nia
authors.forename: Feridoun
authors.initials: F
authors.lastname: Karimi-Busheri
authors.forename: Michael
authors.initials: M
authors.lastname: Weinfeld
mesh_terms: D004249:DNA Damage; D004260:DNA Repair; D015536:Down-Regulation; D006801:Humans; D008969:Molecular Sequence Data; D009153:Mutagens; D009154:Mutation; D011116:Polynucleotide 5'-Hydroxyl-Kinase / Q000235:genetics / Q000378:metabolism*
chemical_list: D009153:Mutagens; D011116:Polynucleotide 5'-Hydroxyl-Kinase