Comparative study of the repair kinetics of chromosomal aberrations and DNA strand breaks in proliferating and quiescent CHO cells.
Repair kinetics observable at the level of exchange-type chromosomal aberrations (dicentric chromosomes), using fractionation and delayed-plating techniques, have been compared with repair kinetics of radiation-induced DNA double-strand breaks, measured with PFGE, and with repair kinetics of all strand breaks, measured with the alkali-unwinding technique. Only data from quiescent or proliferating CHO K1 cells obtained in the same laboratory were used. We determined repair kinetics in terms of the time constant tau (equal to half-time/log(e)2). The repair kinetics (tau approximately 11-14 min) observed in the split-dose formation of dicentric chromosomes agrees with fast repair kinetics of double-strand breaks (tau approximately 11-13 min), thus permitting us to identify the latter as the 'primary lesions' whose pairwise interaction leads to the beta D2 yield term of the aberrations. The repair kinetics observed for dicentric chromosomes formed under delayed-plating conditions (tau approximately 75 min), which mainly affects the alpha D yield term, is attributed to an intermediate interchromosomal product temporarily existing in the course of aberration formation; it is suggested that this product is mechanistically correlated with the slow repair kinetics of 'clustered damage' to DNA seen with the applied molecular methods (tau approximately 90 min).
Greinert
R
R
Institut für Medizinische Physik und Biophysik, Georg-August-Universität Göttingen, Germany.
Volkmer
B
B
Virsik-Peuckert
R P
RP
Harder
D
D
D000818:Animals; D016466:CHO Cells; D002869:Chromosome Aberrations; D006224:Cricetinae; D004249:DNA Damage; D004260:DNA Repair; D007700:Kinetics