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Site-specific DNA cleavage by Chlorella virus topoisomerase II
John M Fortune1, Jennifer S Dickey, Oleg V Lavrukhin
1Departments of Biochemistry and Medicine (Hematology/Oncology), Vanderbilt University School of Medicine, Nashville, TN 37232-0146, USA.
Abstract:
The DNA cleavage reaction of topoisomerase II is central to the catalytic activity of the enzyme and is the target for a number of important anticancer drugs. Unfortunately, efforts to characterize this fundamental reaction have been limited by the low levels of DNA breaks normally generated by the enzyme. Recently, however, a type II topoisomerase with an extraordinarily high intrinsic DNA cleavage activity was isolated from Chlorella virus PBCV-1. To further our understanding of this enzyme, the present study characterized the site-specific DNA cleavage reaction of PBCV-1 topoisomerase II. Results indicate that the viral enzyme cleaves DNA at a limited number of sites. The DNA cleavage site utilization of PBCV-1 topoisomerase II is remarkably similar to that of human topoisomerase IIalpha, but the viral enzyme cleaves these sites to a far greater extent. Finally, PBCV-1 topoisomerase II displays a modest sensitivity to anticancer drugs and DNA damage in a site-specific manner. These findings suggest that PBCV-1 topoisomerase II represents a unique model with which to dissect the DNA cleavage reaction of eukaryotic type II topoisomerases.
Insights
A novel virus enzyme, Chlorella virus PBCV-1 topoisomerase II, offers a powerful new model for studying DNA cleavage. This enzyme, with high DNA cleavage activity, aids in understanding eukaryotic type II topoisomerases and anticancer drug targets.
Area of Science:
- Biochemistry
- Molecular Biology
- Virology
Background:
- Topoisomerase II enzymes are crucial for DNA replication and are targets for anticancer drugs.
- Characterizing the DNA cleavage reaction of topoisomerase II has been challenging due to low DNA break generation.
- A highly active type II topoisomerase was recently isolated from Chlorella virus PBCV-1.
Purpose of the Study:
- To characterize the site-specific DNA cleavage reaction of PBCV-1 topoisomerase II.
- To compare the DNA cleavage activity of PBCV-1 topoisomerase II with human topoisomerase IIalpha.
- To investigate the sensitivity of PBCV-1 topoisomerase II to anticancer drugs and DNA damage.
Main Methods:
- Site-specific DNA cleavage assays using PBCV-1 topoisomerase II.
- Comparative analysis of DNA cleavage site utilization with human topoisomerase IIalpha.
- Assessment of enzyme sensitivity to anticancer drugs and DNA-damaging agents.
Main Results:
- PBCV-1 topoisomerase II cleaves DNA at a restricted set of sites.
- The enzyme's cleavage site utilization closely resembles human topoisomerase IIalpha.
- PBCV-1 topoisomerase II exhibits significantly higher cleavage activity at these sites compared to human enzymes.
- The viral enzyme shows moderate sensitivity to specific anticancer drugs and DNA damage.
Conclusions:
- PBCV-1 topoisomerase II serves as a valuable model for dissecting the DNA cleavage mechanisms of eukaryotic type II topoisomerases.
- The high cleavage activity of the viral enzyme facilitates detailed studies of topoisomerase II function.
- Understanding PBCV-1 topoisomerase II can provide insights into drug development for cancer therapy targeting DNA-related enzymes.