Biomolecular Nanomanipulation

Group leader

February 2014: 2 postdoctoral positions

Our lab focuses on using high-resolution quantitative approaches to gain detailed insight into the mechanisms of DNA transcription, replication and repair, as well as the connections between these processes.

In our research we perform detailed analysis of the kinetic and structural properties of biochemical reactions in vitro using single-molecule manipulation based on magnetic trapping and optical trapping.  Such approaches allow us to characterize rate-limiting reaction intermediates which are difficult, if not impossible, to observe using traditional  ensemble-level bulk biochemistry.

Over the course of the last 15 years the work of the team has focused on the study of protein-DNA interactions.  To given an example, we used single-molecule approaches to study in real-time the process of transcription of DNA into RNA by RNA polymerase, gaining insight into the mechanism whereby RNA polymerase breaks free from the promoter to engage in processive elongation of the transcript (Revyakin et al., 2006).

Strick English

Transcription studies using Magnetic Tweezers
(A) A DNA molecule is bound to a glass surface on one side and a magnetic bead on the other.
(B) The DNA is twisted by turning a pair of magnets above the sample.
(C) When an RNA polymerase molecule attaches to the promoter and unwinds the double helix, tensions decrease and the DNA extension increases.

Now, the technical development of high-resolution optical traps make it possible to measure angstrom-scale displacements with sub-second time resolution.  It therefore has become possible to measure in real time conformational changes in proteins or study in detail protein-protein interactions. 

Our work, at the frontier between biology and physics, focuses on fundamental biological processes such as transcription, replication and repair of DNA.  As the success of these studies depends on technical developments as well as advanced biochemistry, we have equipped ourselves to perform protein purification at the same time as we have developed hybrid “single-molecule” instruments, for instance by coupling magnetic trapping and single-molecule fluorescence detection.  In the medium-term we plan on extending our interests to the study of protein-protein and protein-DNA interactions in vivo using quantitative fluorescence microscopy.

The group is part of the Labex “Who am I?”

Selection of publications

Initiation of transcription-coupled repair characterized at single-molecule resolution.
Howan K, Smith AJ, Westblade LF, Joly N, Grange W, Zorman S, Darst SA, Savery NJ, Strick TR.
Nature. 2012 Oct 18;490(7420):431-4. Epub 2012 Sep 9.

Fast-quantitative single-molecule detection at ultralow concentrations
Haas P, Then P, Wild A, Grange W, Zorman S, Hegner M, Calame M, Uebi A, Flammer J, Hecht B.
Anal. Chem. 82 : 6299–6302 (2010).

VirE2: a unique ssDNA-compacting molecular machine
Grange W, Duckely M, Husale S, Jacob S, Engel , Hegner M.
PLoS Biol. 6 : 343-351 (2008).
Full Text

Abortive initiation and productive initiation by RNA polymerase involve DNA scrunching
Revyakin A, Liu C, Ebright RH, Strick TR.
Science 314 : 1139-1143 (2006).

Single-molecule analysis of DNA uncoiling by a type II topoisomerase.
Strick TR, Croquette V, Bensimon D.
Nature 404 : 901-904 (2000).

Last modified 4 November 2015

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