Display Settings:

Format

Send to:

Choose Destination
See comment in PubMed Commons below
Nature. 2000 Apr 20;404(6780):901-4.

Single-molecule analysis of DNA uncoiling by a type II topoisomerase.

Author information

  • 1Laboratoire de Physique Statistique de l'Ecole Normale Superieure, UMR 8550 CNRS, University of Paris VI, France.

Abstract

Type II DNA topoisomerases are ubiquitous ATP-dependent enzymes capable of transporting a DNA through a transient double-strand break in a second DNA segment. This enables them to untangle DNA and relax the interwound supercoils (plectonemes) that arise in twisted DNA. In vivo, they are responsible for untangling replicated chromosomes and their absence at mitosis or meiosis ultimately causes cell death. Here we describe a micromanipulation experiment in which we follow in real time a single Drosophila melanogaster topoisomerase II acting on a linear DNA molecule which is mechanically stretched and supercoiled. By monitoring the DNA's extension in the presence of ATP, we directly observe the relaxation of two supercoils during a single catalytic turnover. By controlling the force pulling on the molecule, we determine the variation of the reaction rate with the applied stress. Finally, in the absence of ATP, we observe the damping of a DNA crossover by a single topoisomerase on at least two different timescales (configurations). These results show that single molecule experiments are a powerful new tool for the study of topoisomerases.

PMID:
10786800
[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Nature Publishing Group
    Loading ...
    Write to the Help Desk