DNA double-strand break repair defects in syndromes associated with acute radiation response: at least two different assays to predict intrinsic radiosensitivity?
OBJECTIVE
Human diseases associated with acute radiation responses are rare genetic disorders with common clinical and biological features including radiosensitivity, genomic instability, chromosomal aberrations, and frequently immunodeficiency. To determine what molecular assays are predictive of cellular radiosensitivity whatever the genes mutations, the existence of a quantitative correlation between cellular radiosensitivity and unrepaired DNA double-strand breaks (DSB) repair defects was examined in a collection of 40 human fibroblasts representing 8 different syndromes.


METHODS
A number of techniques such as pulsed-field gel electrophoresis, plasmid assay and immunofluorescence with antibodies against MRE11, MDC1, 53BP1 and phosphorylated forms of H2AX, DNA-PK were applied systematically.


CONCLUSIONS
Survival fraction at 2 Gy was found to be inversely proportional to the amount of unrepaired DSB, whatever the genes mutations and the assay applied. However, no single assay discriminates the full range of human radiosensitivity. Particularly, nuclear foci formed by the phosphorylation of H2AX do not predict well moderate radiosensitivities. Our findings suggest the existence of an ATM-dependent interplay between the activation of DNA-PK and MRE11. A classification of diseases according their cellular radiosensitivity, their molecular response to radiation and the functional assays permitting their evaluation is proposed.
Joubert
Aurélie
A
Inserm, U647, ID17, European Synchrotron Radiation Facility, Grenoble, France.
Zimmerman
Kristin M
KM
Bencokova
Zuzana
Z
Gastaldo
Jérôme
J
Chavaudra
Nicole
N
Favaudon
Vincent
V
Arlett
Colin F
CF
Foray
Nicolas
N
D001681:Biological Assay / Q000379:methods; D002460:Cell Line; D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects*; D004249:DNA Damage / Q000502:physiology / Q000528:radiation effects*; D004260:DNA Repair / Q000502:physiology / Q000528:radiation effects*; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D005455:Fluorescent Antibody Technique / Q000379:methods; D005544:Forecasting; D006801:Humans; D011836:Radiation Tolerance / Q000502:physiology / Q000528:radiation effects*; D013997:Time Factors; D014965:X-Rays