Regensburg 2007 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
BP: Fachverband Biologische Physik
BP 10: DNA: supercoils, knots and melting
BP 10.2: Vortrag
Dienstag, 27. März 2007, 14:30–14:45, H43
Sequence-specific Topological Changes of Single DNA Molecules by Human Topoisomerase I in the Presence of Chemotherapeutic Drugs — •Fabian Czerwinski1,2, Daniel Koster1, Ludovic Halby3, Ulrich Schwarz2, Paola B. Arimondo3, and Nynke H. Dekker1 — 1Kavli Institute of Nanoscience, Delft University of Technology, The Netherlands — 2Center for Modelling and Simulation in Biosciences (BIOMS), Universität Heidelberg, Germany — 3UMR5153 CNRS, Paris, France
Human topoisomerase I relaxes the superhelical tension associated with DNA replication, transcription and recombination by generating a transient nick in the DNA duplex. This allows the DNA to swivel about the intact strand before religating. Topoisomerase I is the sole target of the camptothecin family of anticancer compounds which stabilize the covalent enzyme-DNA complex and slow down the removal of DNA supercoils leading to lesions that can induce cell death.
Real-time activity of topoisomerase I can be monitored using magnetic tweezers. Combining these with camptothecin-associated triple-helix formation permits, for the first time, sequence-specific detection of the intercalation of single camptothecins to the enzyme-DNA complex. The imposed sequence-specificity allows repeated interrogation of a well-defined interaction, more clearly exposing the underlying biophysical processes. In the presence of a single camptothecin, the swivel rate is lower for the removal of positive supercoils than for negative ones, in agreement with in vivo experiments showing an accumulation of positive DNA supercoils in drug-treated cells.