Studies on DNA Topoisomerase activity during in vitro chromatin assembly |
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Authors: | Jo Ann M. ISekiguchi Eric B. Kmiec |
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Affiliation: | (1) Department of Biochemistry and Biophysics, University of California at Davis, 95616 Davis, California, USA |
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Abstract: | The in vitro assembly of chromatin, promoted by the Xenopus cell-free extract (S-150), can be inhibited by oxolinic acid and to a lesser extent by nalidixic acid. Both of these antibiotics have been shown to block the activity of the specialized type 11 Topoisomerase, bacterial DNA Gyrase. Oxolinic acid induces a DNA cleavage by Micrococcal Nuclease at specific sequences in the multiple cloning vector pGEM-4. Nalidixic acid does not inhibit DNA supercoiling, but does diminish the extent of chromatin formation achieved by the S-150 on circular DNA templates. The Topoisomerase I inhibitor, berenil, does not inhibit extensive chromatin assembly, although it aloes diminish the level of supercoiling. Taken together, these results suggest that both topoisomerases play a role in the assembly process. Topoisomerase I may catalyze both the introduction of unconstrained supercoils into relaxed DNA and the formation of monosomes, while Topoisomerase 11 may promote extended chromatin assembly. |
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Keywords: | chromatin assembly Type I Topoisomerases DNA gyration |
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