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Updated: Oct 15, 2026
Laser Microirradiation to Study In Vivo Cellular Responses to Simple and Complex DNA Damage
Published on: January 31, 2018
The effects of microgravity on ligase activity in the repair of DNA double-strand breaks
A Takahashi1, K Ohnishi, S Takahashi
1Department of Biology, Nara Medical University, Japan.
Purpose:
In recent years, contradictory data have been reported about the effects of microgravity on radiation-induced biological responses in space experiments. The aim of the present study was to clarify whether enzymatic repair of DNA double-strand breaks is affected by microgravity using an in vitro enzymatic reaction system.
Materials And Methods:
The DNA repair activity of T4 DNA ligase (EC 6.5.1.1) was measured in vitro for a DNA substrate damaged by restriction enzyme digestion during a US Space Shuttle mission (Discovery; STS-91). After the flight, the amount of ligated DNA molecules was measured using an electrophoresis method.
Results:
Ligated products (closed circular DNA, open circular DNA and multimeric ligated products) were produced by T4 DNA ligase treatment of linear DNA containing double-strand breaks, and they increased with increasing T4 DNA ligase concentration (0-3 units per microg of plasmid DNA). Almost no difference in T4 DNA ligase activity was detected between the space experiments and the control ground experiments.
Conclusions:
No significant effect of microgravity on ligation of damaged DNA was found during space flight. Therefore, other mechanisms must account for the synergism between radiation and microgravity, if it exists.
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