Environmental and Molecular Mutagenesis - Legacy Tobacco ...

90 1989 EMS Abstracts
Notes
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
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THE EFFECT OF THYMIDINE ANALOGUES ON RESTRICTION ENDONUCt .EASE INDUCED
CHROMOSOME ABERRATIONS. OJ. Hook. R.J . Preston, University of Tennessee Biomedical Graduate Sclwol,
and Biology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 .
The thymidine analogue CIdU has been used to analyze the Importance of reoombination-like repair on the
frequency and type of chromosome aberrations (CAs) inductd by X rays . The results of these experiments
demonstrated that the level of CAs induced by X rays eould be enhanced and the proportion of exchange type
aberrations Increased when CIdU was present in the template during 03 repair . CIdU Incorporation b a useful
method of analyzing the Importance of excision repair on the formation of CAs Induced in Or 7ype 11 restriction
endonucleases (REa) have Iken shown to induce CAs in mammalian cells in all parts of the cell cycle Including O, .
We propose to test the bypotbeses that repair of RE induee double strand cuts involves more than simple ligation
and the extent to which induced CAs are the result of lack of repair of the Induced double strand cuts as opposed
to misrepair. CHO cells grown in the presence of CIdU were treated with Sau 3A1 at concentrations of 10 and 25
units per 100 pl using the 'osmolytic shock' protocol . The cells were grown In the presence of CIdU for 26 hrs
before treatment and harvested 4 hrs after treatment . Astoradiography has shown that the majority of cells
harvested at 4 bn post-treatment were In O= or M when treated . The presence of CIdU (concentration 30yM)
resulted In a reduction in the level of deletion type CAs and a doubling of the number of exchange type CAs above
that expected from additivity. No Increase over additivity was observed when CHO cells were grown in the presence
of BrdU. In conclusion, RE induced double strand cuts are, in part, repaired by a mechanism that Involves a
resynthesis step . By altering the likelihood of misrepalr the damage that would have been converted Into deletion
type aberrations was converted into exchange type aberrationt . (Research sponsored by the Office of Health and
Environmental Reaearch, U. S. Department of Energy under contract DE-ACUS-840R21400 with the Martin Marietta
Energy Systems, Inc .)
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RESTRICTION ENZYMI