Supercoiling DNA optically

Cellular DNA is regularly subject to torsional stress during genomic processes, such as transcription and replication, resulting in a range of supercoiled DNA structures. For this reason, methods to prepare and study supercoiled DNA at the single-molecule level are widely used, including magnetic, angular-optical, micropipette, and magneto-optical tweezers. However, it is currently challenging to combine DNA supercoiling control with spatial manipulation and fluorescence microscopy. This limits the ability to study complex and dynamic interactions of supercoiled DNA. Here we present a single-molecule assay that can rapidly and controllably generate negatively supercoiled DNA using a standard dual-trap optical tweezers instrument. This method, termed Optical DNA Supercoiling (ODS), uniquely combines the ability to study supercoiled DNA using force spectroscopy, fluorescence imaging of the whole DNA, and rapid buffer exchange. The technique can be used to generate a wide range of supercoiled states, with between <5 and 70% lower helical twist than nonsupercoiled DNA. Highlighting the versatility of ODS, we reveal previously unobserved effects of ionic strength and sequence on the structural state of underwound DNA. Next, we demonstrate that ODS can be used to directly visualize and quantify protein dynamics on supercoiled DNA. We show that the diffusion of the mitochondrial transcription factor TFAM can be significantly hindered by local regions of underwound DNA. This finding suggests a mechanism by which supercoiling could regulate mitochondrial transcription in vivo. Taken together, we propose that ODS represents a powerful method to study both the biophysical properties and biological interactions of negatively supercoiled DNA.

Medienart:

E-Artikel

Erscheinungsjahr:

2019

Erschienen:

2019

Enthalten in:

Zur Gesamtaufnahme - volume:116

Enthalten in:

Proceedings of the National Academy of Sciences of the United States of America - 116(2019), 52 vom: 26. Dez., Seite 26534-26539

Sprache:

Englisch

Beteiligte Personen:

King, Graeme A [VerfasserIn]
Burla, Federica [VerfasserIn]
Peterman, Erwin J G [VerfasserIn]
Wuite, Gijs J L [VerfasserIn]

Links:

Volltext

Themen:

DNA–protein interactions
DNA supercoiling
Fluorescence microscopy
Journal Article
Optical tweezers

Anmerkungen:

Date Revised 05.12.2022

published: Print-Electronic

Citation Status PubMed-not-MEDLINE

doi:

10.1073/pnas.1908826116

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM304084131