title: DNA repair after X-irradiation: lessons from plants.
abstract: The effects of low-dose radiation causing DNA damage continue to be subjects of interest. Problems with existing approaches to low-dose DNA damage are that single-strand breaks (the predominant radiation-induced lesion) are very rapidly repaired and that results using current methods for measuring DNA damage can be difficult to interpret. As a novel approach, we conducted studies using plants (rye grass and the model plant Arabidopsis) exposed to X-rays and used the alkaline comet assay to measure DNA damage and repair after exposures. Consistent with previous studies, we detected so-called 'rapid' and 'slow' phases of DNA repair after acute exposures of 5 and 15 Gy. After exposures corresponding to 2 Gy and lower, 'rapid' repair was so fast that it was difficult to detect. We also found that the so-called 'slow' phase in both plants actually consisted of two components; an initial period of negligible repair lasting 80-120 min followed by a period of rapid repair lasting <30 min. Using Arabidopsis mutants homozygous for both ATM and BRCA1, we found that both of these genes are required for DNA repair during the 3-h period of our experiments, indicating that the 'slow' phase involves a homologous repair (HR) of double-strand breaks and clustered single-strand breaks. The lag of repair in the 'slow' phase presumably involves induction of expression of genes involved in HR repair such as BRCA1 and RAD51.
authors.affiliation: Department of Nutrition, Faculty of Medicine, University of Oslo, 0316 Oslo, Norway john.einset@nmbu.no.
authors.forename: John
authors.initials: J
authors.lastname: Einset
authors.affiliation: Department of Nutrition, Faculty of Medicine, University of Oslo, 0316 Oslo, Norway.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Collins
mesh_terms: D000704:Analysis of Variance; D017360:Arabidopsis / Q000235:genetics / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism; D020552:Comet Assay / Q000379:methods*; D004249:DNA Damage / Q000235:genetics*; D004307:Dose-Response Relationship, Radiation; D008129:Lolium / Q000235:genetics / Q000528:radiation effects*; D008856:Microscopy, Fluorescence; D013997:Time Factors; D014965:X-Rays / Q000009:adverse effects*
chemical_list: C576589:ATM protein, Arabidopsis; D029681:Arabidopsis Proteins; D019313:BRCA1 Protein; D064007:Ataxia Telangiectasia Mutated Proteins