Repair of radiation-induced DNA double-strand breaks in human fibroblasts is consistent with a continuous spectrum of repair probability.
OBJECTIVE
To propose a novel interpretation of DNA double-strand break (dsb) repair based on the distribution of energy micro-deposition.


METHODS
Double-strand break repair curves were studied either after irradiation at 4 degrees C or at 37 degrees C (low dose rate). Two human fibroblast cell lines were used: a control line, HF19, and an ataxia telangiectasia repair-deficient line, AT5BI. Irradiations were made with gamma-rays or alpha-particles (241Am). Repair data were fitted by the variable repair half-time (VRHT) model. Assuming that each dsb has its own inherent repair half-time (IRHT) and that the VRHT is the average of the IRHT at any time during repair, the distribution of the IRHT was calculated.


RESULTS
At the end of the irradiation, the distribution was a continuous asymmetric curve with a maximum of dsb having a short IRHT. After 1 h of repair, the curve became bell-shaped. There is a striking similarity between the distribution of dsb repair half-times and that of energy micro-deposition described by Goodhead et al. (1993).


CONCLUSIONS
This similarity suggests a possible causal relationship between the energy density deposition and the repair rate or the probability of dsb repair.
Foray
N
N
UMR 1599 CNRS - PR1 - Institut Gustave-Roussy, Villejuif, France. nforay@igr.fr
Monroco
C
C
Marples
B
B
Hendry
J H
JH
Fertil
B
B
Goodhead
D T
DT
Arlett
C F
CF
Malaise
E P
EP
D000576:Americium; D002460:Cell Line / Q000528:radiation effects; D004247:DNA / Q000528:radiation effects*; D004260:DNA Repair; D005347:Fibroblasts / Q000528:radiation effects; D006801:Humans; D013696:Temperature; D013997:Time Factors
D004247:DNA; D000576:Americium