Evidence that unrejoined DNA double-strand breaks are not predominantly responsible for chromosomal radiosensitivity of AT fibroblasts

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13 Citations (Scopus)

Abstract

To examine more fully the nature of chromosomal radiosensitivity in ataxia telangiectasia (AT) cells, we employed 24-color combinatorial painting to visualize 137CS γ-ray-induced chromosome-type aberrations in cells of two AT and one normal primary human fibroblast strains irradiated in log-phase growth. As a measure of misrejoined radiation-induced DSBs, we quantified exchange breakpoints associated with both simple and complex exchanges. As a measure of unrejoined DSBs, we quantified breakpoints from terminal deletions as well as deletions associated with incomplete exchange. For each of these end points, the frequency of damage per unit dose was markedly higher in AT cells compared to normal cells, although the proportion of total breaks that remained unrejoined was rather similar. The majority of breakpoints in both cell types were involved in exchanges. AT cells had a much higher frequency of complex exchanges compared to normal cells given the same dose, but for doses that resulted in approximately the same level of total breakpoints, the relative contribution from complex damage was also similar. We conclude that although terminal deletions and incomplete exchanges contribute to AT cell radiosensitivity, their relative abundance does not-in apparent contrast to the situation in lymphoblastoid cells-overwhelmingly account for the increased damage we observed in cycling AT fibroblasts. Thus, from a cytogenetic perspective, a higher level of unrepaired DSBs does not provide a universal explanation for the radiation-sensitive AT phenotype.

Original languageEnglish
Pages (from-to)554-565
Number of pages12
JournalRadiation Research
Volume162
Issue number5
DOIs
StatePublished - Nov 2004

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ataxia
Ataxia Telangiectasia
Double-Stranded DNA Breaks
Radiation Tolerance
fibroblasts
radiation tolerance
strands
deoxyribonucleic acid
Fibroblasts
DNA
cells
deletion
damage
dosage
Radiation
Paintings
phenotype
chromosomes
radiation
cytogenetics

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Radiology Nuclear Medicine and imaging
  • Biophysics
  • Radiation

Cite this

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abstract = "To examine more fully the nature of chromosomal radiosensitivity in ataxia telangiectasia (AT) cells, we employed 24-color combinatorial painting to visualize 137CS γ-ray-induced chromosome-type aberrations in cells of two AT and one normal primary human fibroblast strains irradiated in log-phase growth. As a measure of misrejoined radiation-induced DSBs, we quantified exchange breakpoints associated with both simple and complex exchanges. As a measure of unrejoined DSBs, we quantified breakpoints from terminal deletions as well as deletions associated with incomplete exchange. For each of these end points, the frequency of damage per unit dose was markedly higher in AT cells compared to normal cells, although the proportion of total breaks that remained unrejoined was rather similar. The majority of breakpoints in both cell types were involved in exchanges. AT cells had a much higher frequency of complex exchanges compared to normal cells given the same dose, but for doses that resulted in approximately the same level of total breakpoints, the relative contribution from complex damage was also similar. We conclude that although terminal deletions and incomplete exchanges contribute to AT cell radiosensitivity, their relative abundance does not-in apparent contrast to the situation in lymphoblastoid cells-overwhelmingly account for the increased damage we observed in cycling AT fibroblasts. Thus, from a cytogenetic perspective, a higher level of unrepaired DSBs does not provide a universal explanation for the radiation-sensitive AT phenotype.",
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