Light-induced transient increase of the activity of topoisomerase I in plasmodia of Physarum polycephalum |
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Institution: | Institute of Biochemistry, Warsaw University, Al. Zwirki i Wigury 93, 02-089 Warszawa, Poland |
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Abstract: | - 1.1. Activity of topoisomerase I and incorporation of 3H]uridine and 14C]thymidine were monitored during light-induced sporulation of the slime mold Physarum polycephalun.
- 2.2. A 4-fold transient increase of topoisomerase I activity but not of 3H]uridine or 14C]thymidine incorporation was observed after 42 hr of illumination with 6 hr impulses.
- 3.3. The activity of topoisomerase I did not increase in the absence of light impulses. However, ca 5-fold increase of the activity was observed in dark when 100 μ M dibutyryl-cAMP was administered 12 hr before harvesting of plasmodia.
- 4.4. Fluorodeoxyuridine and cycloheximide administered 36 hr after starting of the illumination cancelled the increase of the activity of topoisomerase I.
- 5.5. After 7 days of the illumination, when fruiting bodies appeared, the activity of topoisomerase I dropped to about 15% of the initial value.
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