title: Association of ATM activation and DNA repair with induced radioresistance after low-dose irradiation.
abstract: Mammalian cells often exhibit a hyper-radiosensitivity (HRS) to radiation doses <20 cGy, followed by increased radioresistance (IRR) at slightly higher doses (∼20-30 cGy). Here, the influence of DNA double-strand break repair (DSBR) on IRR was examined. The failure of Ataxia telangiectasia (AT) cells to undergo IRR reported by others was confirmed. Flow cytometric analysis indicated that normal cells fail to show a measurable increase in serine 1981 phosphorylated AT-mutated (ATM) protein after 10 cGy up to 4 h post irradiation, but a two- to fourfold increase after 25 cGy. Similarly, more proficient reduction of phosphorylated histone H2AX was observed 24 h after 25 cGy than after 10 cGy, suggesting that DSBR is more efficient during IRR than HRS. A direct examination of the consequences of inefficient DNA repair per se (as opposed to ATM-mediated signal transduction/cell cycle responses), by determining the clonogenic survival of cells lacking the DNA repair enzyme polynucleotide kinase/phosphatase, indicated that these cells have a response similar to AT cells, i.e. HRS but no IRR, strongly linking IRR to DSBR.
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Enns
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Rasouli-Nia
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Hendzel
authors.affiliation: Department of Radiation Oncology, William Beaumont Hospital, 3811 W. Thirteen Mile Rd., 105-RI, Royal Oak, MI 48073, USA.
authors.forename: B
authors.initials: B
authors.lastname: Marples
authors.affiliation: Department of Oncology, University of Alberta, Cross Cancer Institute, 11560 University Ave., Edmonton, Alberta T6G 1Z2, Canada mweinfel@ualberta.ca.
authors.forename: M
authors.initials: M
authors.lastname: Weinfeld
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects*; D002478:Cells, Cultured; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects*; D004260:DNA Repair / Q000528:radiation effects*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D005434:Flow Cytometry; D005720:Gamma Rays / Q000009:adverse effects*; D006657:Histones / Q000378:metabolism; D006801:Humans; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000528:radiation effects; D000069079:Radiation Exposure / Q000009:adverse effects; D011836:Radiation Tolerance / Q000235:genetics*; D015398:Signal Transduction; D012867:Skin / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects
chemical_list: D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins