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.
Department of Radiation Biology, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, UK. ugenskiene@yahoo.com
Rasa
R
Ugenskiene
Kevin
K
Prise
Melvyn
M
Folkard
Janusz
J
Lekki
Zbigniew
Z
Stachura
Monika
M
Zazula
Jerzy
J
Stachura
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