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Radiation-induced heat-labile sites that convert into DNA double-strand breaksThe yield of DNA double-strand breaks (DSBs) in SV40 DNA irradiated in aqueous solution was found to increase by more than a factor of two as a result of postirradiation incubation of the DNA at 50 degrees C and pH 8.0 for 24 h. This is in agreement with data from studies performed at 37 degrees C that were published previously. Importantly, similar results were also obtained from irradiation of mammalian DNA in agarose plugs. These results suggest that heat-labile sites within locally multiply damaged sites are produced by radiation and are subsequently transformed into DSBs. Since incubation at 50 degrees C is typically employed for lysis of cells in commonly used pulsed-field gel assays for detection of DSBs in mammalian cells, the possibility that heat-labile sites are present in irradiated cells was also studied. An increase in the apparent number of DSBs as a function of lysis time at 50 degrees C was found with kinetics that was similar to that for irradiated DNA, although the magnitude of the increase was smaller. This suggests that heat-labile sites are also formed in the cell. If this is the case, a proportion of DSBs measured by the pulsed-field gel assays may occur during the lysis step and may not be present in the cell as breaks but as heat-labile sites. It is suggested that such sites consist mainly of heat-labile sugar lesions within locally multiply damaged sites. Comparing rejoining of DSBs measured with short and long lysis procedure indicates that the heat-labile sites are repaired with fast kinetics in comparison with repair of the bulk of DSBs.
Document ID
20040141553
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Rydberg, B.
(Lawrence Berkeley National Laboratory, Life Sciences Division One Cyclotron Road, Building 74, Berkeley, California 94720, United States)
Chatterjee, A.
Date Acquired
August 22, 2013
Publication Date
June 1, 2000
Publication Information
Publication: Radiation research
Volume: 153
Issue: 6
ISSN: 0033-7587
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: CA80207
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Radiation Health

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