title: Silencing expression of the catalytic subunit of DNA-dependent protein kinase by small interfering RNA sensitizes human cells for radiation-induced chromosome damage, cell killing, and mutation.
abstract: Targeted gene silencing in mammalian cells by RNA interference (RNAi) using small interfering RNAs (siRNAs) was recently described by Elbashir et al. (S. M. Elbashir et al., Nature (Lond.), 411: 494-498, 2001). We have used this methodology in several human cell strains to reduce expression of the Prkdc (DNA-PKcs) gene coding for the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) that is involved in the nonhomologous end joining of DNA double-strand breaks. We have also demonstrated a radiosensitization for several phenotypic endpoints of radiation damage. In low-passage normal human fibroblasts, siRNA knock-down of DNA-PKcs resulted in a reduced capacity for restitution of radiation-induced interphase chromosome breaks as measured by premature chromosome condensation, an increased yield of acentric chromosome fragments at the first postirradiation mitosis, and an increased radiosensitivity for cell killing. For three strains of related human lymphoblasts, DNA-PKcs-targeted siRNA transfection resulted in little or no increase in radiosensitivity with respect to cell killing, a 1.5-fold decrease in induced mutant yield in TK6- and p53-null NH32 cells, but about a 2-fold increase in induced mutant yield in p53-mutant WTK1 cells at both the hypoxanthine quanine phosphoribosyl transferase (hprt) and the thymidine kinase loci.
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University Fort Collins, Colorado 80523-1681, USA.
authors.forename: Yuanlin
authors.initials: Y
authors.lastname: Peng
authors.forename: Qinming
authors.initials: Q
authors.lastname: Zhang
authors.forename: Hatsumi
authors.initials: H
authors.lastname: Nagasawa
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Okayasu
authors.forename: Howard L
authors.initials: HL
authors.lastname: Liber
authors.forename: Joel S
authors.initials: JS
authors.lastname: Bedford
mesh_terms: D002384:Catalysis; D016923:Cell Death / Q000528:radiation effects; D002478:Cells, Cultured; D002869:Chromosome Aberrations / Q000528:radiation effects*; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology / Q000528:radiation effects; D020868:Gene Silencing; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000528:radiation effects; D016296:Mutagenesis / Q000528:radiation effects; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics*; D034741:RNA, Small Interfering / Q000235:genetics*; D011836:Radiation Tolerance / Q000235:genetics*; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases