Friction and torque govern the relaxation of DNA supercoils by eukaryotic topoisomerase IB Journal Article
| Authors: | Koster, D. A.; Croquette, V.; Dekker, C.; Shuman, S.; Dekker, N. H. |
| Article Title: | Friction and torque govern the relaxation of DNA supercoils by eukaryotic topoisomerase IB |
| Abstract: | Topoisomerases relieve the torsional strain in DNA that is built up during replication and transcription. They are vital for cell proliferation and are a target for poisoning by anti-cancer drugs. Type IB topoisomerase (TopIB) forms a protein clamp around the DNA duplex and creates a transient nick that permits removal of supercoils. Using real-time single-molecule observation, we show that TopIB releases supercoils by a swivel mechanism that involves friction between the rotating DNA and the enzyme cavity: that is, the DNA does not freely rotate. Unlike a nicking enzyme, TopIB does not release all the supercoils at once, but it typically does so in multiple steps. The number of supercoils removed per step follows an exponential distribution. The enzyme is found to be torque-sensitive, as the mean number of supercoils per step increases with the torque stored in the DNA. We propose a model for topoisomerization in which the torque drives the DNA rotation over a rugged periodic energy landscape in which the topoisomerase has a small but quantifiable probability to religate the DNA once per turn. |
| Keywords: | unclassified drug; nonhuman; mutant protein; cell proliferation; proteins; metabolism; biological model; models, biological; enzymology; enzyme activity; chemistry; dna; double stranded dna; vaccinia virus; thermodynamics; conformation; nucleic acid conformation; eukaryotic cell; enzymes; eukaryote; dna topoisomerase; dna topoisomerases, type i; velocity; isomerization; cells; molecules; dna supercoiling; dna, superhelical; rotation; torque; eukaryotic cells; magnetic field; friction; anti-cancer drugs; topoisomerization; torsional strain; dna topoisomerase ib |
| Journal Title: | Nature |
| Volume: | 434 |
| Issue: | 7033 |
| ISSN: | 0028-0836 |
| Publisher: | Nature Publishing Group |
| Date Published: | 2005-03-31 |
| Start Page: | 671 |
| End Page: | 674 |
| Language: | English |
| DOI: | 10.1038/nature03395 |
| PUBMED: | 15800630 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | --- - "Cited By (since 1996): 117" - "Export Date: 24 October 2012" - "CODEN: NATUA" - "Source: Scopus" |
