BRCA1 role in the mitigation of radiotoxicity and chromosomal instability through repair of clustered DNA lesions |
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| Authors: | Jessica M Hair Georgia I Terzoudi Vasiliki I Hatzi Katie A Lehockey Devika Srivastava Weixin Wang Gabriel E Pantelias Alexandros G Georgakilas |
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| Institution: | 1. Department of Biology, Thomas Harriot College of Arts and Sciences, East Carolina University, Greenville, NC 27858, USA;2. Radiobiology and Cytogenetics, National Center for Scientific Research ‘Demokritos’, Aghia Paraskevi 15310, Athens, Greece;3. Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD 20892, USA;1. Brigham and Women''s Hospital, Dana Farber Cancer Institute, and Harvard Medical School, Boston, Massachusetts;2. University of Massachusetts, Lowell, Massachusetts;3. Ocean Road Cancer Institute, Dar Es Salaam, Tanzania;4. Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts;6. Dana Farber Cancer Institute, Boston, Massachusetts;5. International Atomic Energy Agency, Vienna, Austria;7. Space Coast Cancer Center, Titusville, Florida;11. African Renaissance Ambassador Corporation, Orlando, Florida;12. MD Anderson Cancer Center, Houston, Texas;8. African Organization for Research and Training in Cancer, Rondebosch, South Africa;10. University of Florida, Gainesville, Florida;9. International Organization for Medical Physics, University of Arizona Cancer Center, Phoenix, Arizona;3. Department of Chemistry, Purdue University, West Lafayette, Indiana 47907;4. Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa 52242;5. NMR Facility, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242;6. Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa 52242;1. Department of Radiology, Charité–Universitätsmedizin Berlin, Augustenburger Platz 1, 13353 Berlin, Germany;2. Berlin Institute of Health, Berlin, Germany;1. Department of Urology, Nara Medical University, Japan;2. Department of Radiation Oncology, Nara Medical University, Japan;3. Department of Pathology, Nara Medical University, Japan;1. School of Public Health and Health Systems, University of Waterloo, Waterloo, Ontario, Canada;2. Schlegel-UW Research Institute for Aging, University of Waterloo, Waterloo, Ontario, Canada;3. Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada |
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| Abstract: | Oxidatively-induced clustered DNA lesions are considered the signature of any ionizing radiation like the ones human beings are exposed daily from various environmental sources (medical X-rays, radon, etc.). To evaluate the role of BRCA1 deficiencies in the mitigation of radiation-induced toxicity and chromosomal instability we have used two human breast cancer cell lines, the BRCA1 deficient HCC1937 cells and as a control the BRCA1 wild-type MCF-7 cells. As an additional control for the DNA damage repair measurements, the HCC1937 cells with partially reconstituted BRCA1 expression were used. Since clustered DNA damage is considered the signature of ionizing radiation, we have measured the repair of double strand breaks (DSBs), non-DSB bistranded oxidative clustered DNA lesions (OCDLs) as well as single strand breaks (SSBs) in cells exposed to radiotherapy-relevant γ-ray doses. Parallel measurements were performed in the accumulation of chromatid and isochromatid breaks. For the measurement of OCDL repair, we have used a novel adaptation of the denaturing single cell gel electrophoresis (Comet assay) and pulsed field gel electrophoresis with Escherichia coli repair enzymes as DNA damage probes. Independent monitoring of the γ-H2AX foci was also performed while metaphase chromatid lesions were measured as an indicator of chromosomal instability. HCC1937 cells showed a significant accumulation of all types of DNA damage and chromatid breaks compared to MCF-7 while BRCA1 partial expression contributed significantly in the overall repair of OCDLs. These results further support the biological significance of repair resistant clustered DNA damage leading to chromosomal instability. The current results combined with previous findings on the minimized ability of base clusters to induce cell death (mainly induced by DSBs), enhance the potential association of OCDLs with breast cancer development especially in the case of a BRCA1 deficiency leading to the survival of breast cells carrying a high load of unrepaired DNA damage clusters. |
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