Misrepair of DNA double-strand breaks in patient with unidentified chromosomal fragility syndrome and family history of radiosensitivity

Abstract

Purpose: To test the hypothesis that differences in DNA double-strand breaks (DSB) repair fidelity underlies differences in radiosensitivity.

Materials and methods: A primary fibroblast culture (C42) derived from a pediatric cancer patient treated with reduced radiation doses consequent to a family history of radiosensitivity reminiscent of chromosomal fragility syndrome, was compared to a normal control (C29). DNA DSB rejoining and repair fidelity were studied by Southern blotting and hybridization to specific fragments: Alu repetitive sequence representing the overall DSB rejoining capacity in the genome and a 3.2 Mbp NotI restriction fragment on chromosome 21 for DSB repair fidelity.

Results: Although both assays showed statistically significant difference (p ≤ 0.05) between the two cell strains in residual misrepaired (un-or mis-rejoined) DSB (24 h after 30 or 80 Gy), the residual damage was lower in the Alu enriched genome assay compared to NotI assay (0.01–0.07 and 0.10–0.37, respectively).

Conclusions: These results suggest that, in comparison to classic DSB repair experiment, an assay of measuring DNA DSB repair fidelity can provide better resolution and a more accurate estimate of misrepair of radiation-induced DNA damage, which underlies genomic instability and increased radiosensitivity.

Keywords::

• DNA double-strand breaks
• misrepair
• NotI fragment
• PFGE
• human fibroblasts
• radiosensitivity

Acknowledgements

We thank Ms Sherri Bergh, Najla Al-Harbi, Khaled Al-Hadyan and Nikki Venturina for their technical assistance.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

We acknowledge the previous support of National Cancer Institute (NCI) grants CA06294 and CA-16672 and the current funding by King Abdulaziz City for Science & Technology (KACST) under the National Science, Technology & Innovation Plan (NSTIP) grant 9-MED749-20 (KFSHRC RAC#2110 005).