Topoisomerase II from Chlorella Virus PBCV-1 Has an Exceptionally High DNA Cleavage Activity
Chlorella virus PBCV-1 topoisomerase II is the only functional type II enzyme known to be encoded by a virus that infects eukaryotic cells. However, it has not been established whether the protein is expressed following viral infection or whether the enzyme has any catalytic features that distinguis...
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Veröffentlicht in: | The Journal of biological chemistry 2001-06, Vol.276 (26), p.24401-24408 |
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Sprache: | eng |
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Zusammenfassung: | Chlorella virus PBCV-1 topoisomerase II is the only functional type II enzyme known to be encoded by a virus that infects eukaryotic cells. However, it has not been established whether the protein is expressed following viral infection or whether the enzyme has any catalytic features that distinguish it from cellular type II topoisomerases. Therefore, the present study characterized the physiological expression of PBCV-1 topoisomerase II and individual reaction steps catalyzed by the enzyme. Results indicate that the topoisomerase II gene is widely distributed among Chlorellaviruses and that the protein is expressed 60–90 min after viral infection of algal cells. Furthermore, the enzyme has an extremely high DNA cleavage activity that sets it apart from all known eukaryotic type II topoisomerases. Levels of DNA scission generated by the viral enzyme are ∼30 times greater than those observed with human topoisomerase IIα. The high levels of cleavage are not due to inordinately tight enzyme-DNA binding or to impaired DNA religation. Thus, they most likely reflect an elevated forward rate of scission. The robust DNA cleavage activity of PBCV-1 topoisomerase II provides a unique tool for studying the catalytic functions of type II topoisomerases. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M101693200 |