Mutagenesis Advance Access originally published online on July 14, 2007
Mutagenesis 2007 22(5):359-362; doi:10.1093/mutage/gem026
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A comparison of G2 phase radiation-induced chromatid break kinetics using calyculin-PCC with those obtained using colcemid block
Bute Medical School, University of St Andrews, St Andrews KY16 9TS, UK 1Department of Medical Genetics, School of Medical Sciences, Tarbiat Modares University, PO Box:14115-111, Tehran, Islamic Republic of Iran
To study the possible influence of cell-cycle delay on cells reaching mitosis during conventional radiation-induced chromatid break experiments using colcemid as a blocking agent, we have compared the chromatid break kinetics following a single dose of gamma rays (0.75 Gy) in metaphase CHO cells using calyculin-induced premature chromosome condensation (PCC), with those using colcemid block. Calyculin-induced PCC causes very rapid condensation of G2 cell chromosomes without the need for a cell to progress to mitosis, hence eliminating any effect of cell-cycle checkpoint on chromatid break frequency. We found that the kinetics of the exponential first-order decrease in chromatid breaks with time after irradiation was similar (not significantly different) between the two methods of chromosome condensation. However, use of the calyculin-PCC technique resulted in a slightly increased rate of disappearance of chromatid breaks and thus higher frequencies of breaks at 1.5 and 2.5 h following irradiation. We also report on the effect of the nucleoside analogue ara A on chromatid break kinetics using the two chromosome condensation techniques. Ara A treatment of cells abrogated the decrease in chromatid breaks with time, both using the calyculin-PCC and colcemid methods. We conclude that cell-cycle delay may be a factor determining the absolute frequency of chromatid breaks at various times following irradiation of cells in G2 phase but that the first-order disappearance of chromatid breaks with time and its abrogation by ara A are not significantly influenced by the G2 checkpoint.
* To whom correspondence should be addressed. Tel: +01334 463 510; Fax: +01334 463 482; Email: peb{at}st-and.ac.uk
Received on March 16, 2007; revised on May 22, 2007; accepted on May 30, 2007.
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O. Shovman, A. C. Riches, D. Adamson, and P. E. Bryant An improved assay for radiation-induced chromatid breaks using a colcemid block and calyculin-induced PCC combination Mutagenesis, July 1, 2008; 23(4): 267 - 270. [Abstract] [Full Text] [PDF] |
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