Dose response and kinetics of foci disappearance following exposure to high- and low-LET ionizing radiation.
OBJECTIVE
The effect of different radiation qualities on (i) 53BP1 (p53 Binding Protein 1) and p-ATM (phosphorylated ataxia telangiectasia mutated) foci induction, and (ii) on the kinetics of foci disappearance was analysed.


METHODS
Normal human skin fibroblasts were exposed to 240 kV broad-field X-rays or targeted with individually counted helium ((3)He) particles or protons ((1)H) from a Charged Particle Microbeam. Anti-p-ATM and anti-53BP1 antibodies were used for foci visualisation via immunocytochemistry.


RESULTS
1 Gy of X-rays yielded approximately 33 53BP1-positive foci/cell. The ratio between the number of delivered particles and yielded tracks was found to be 1:1 and 3:1 after targeted (3)He and (1)H irradiation, respectively. It was determined that approximately 50% of radiation-induced damage was repaired as measured by loss of foci during the first 2, 6, and 10 hours following X-ray, protons, and (3)He irradiation, respectively.


CONCLUSIONS
There was significant radiation quality dependence for 53BP1- and p-ATM-positive foci induction observed. Foci disappearance was radiation dose-independent in the samples irradiated with X-rays. Our results confirm that kinetics of foci disappearance depends on radiation quality, even when individual ions are targeted to cells.
Ugenskiene
Rasa
R
Department of Radiation Biology, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, UK. ugenskiene@yahoo.com
Prise
Kevin
K
Folkard
Melvyn
M
Lekki
Janusz
J
Stachura
Zbigniew
Z
Zazula
Monika
M
Stachura
Jerzy
J
D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000528:radiation effects*; D002460:Cell Line; D002467:Cell Nucleus / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded / Q000528:radiation effects; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure; D006371:Helium; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism / Q000528:radiation effects*; D007700:Kinetics; D018499:Linear Energy Transfer; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000528:radiation effects*; D011522:Protons; D012062:Relative Biological Effectiveness; D025521:Tumor Suppressor Proteins / Q000378:metabolism / Q000528:radiation effects*; D000071857:Tumor Suppressor p53-Binding Protein 1
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011522:Protons; C498301:TP53BP1 protein, human; D025521:Tumor Suppressor Proteins; D000071857:Tumor Suppressor p53-Binding Protein 1; D006371:Helium; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases