Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

DNA Helicases

DNA Helicases

DNA unwinding helicase enzymes are a type of motor protein. Motor proteins can translocate along filaments or polymers using energy generated from ATP hydrolysis. Helicases are involved in all the important cellular processes where DNA unwinding is required, such as DNA replication, repair, recombination, and transcription. They are present in all living organisms, but vary in their structure, function, and mechanism of action. For example, in prokaryotes, DnaB helicase binds and translocates...

DNA Topoisomerases

DNA Topoisomerases

Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...

The DNA Replication Fork

The DNA Replication Fork

An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork. Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...

The DNA Replication Fork

The DNA Replication Fork

An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork. Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...

Restarting Stalled Replication Forks

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...

Homologous Recombination

Homologous Recombination

The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Photoprotection in a desert moss: dynamic excitation quenching during the hydration cycle of the Syntrichia caninervis.

Photosynthesis research·2026

Same author

Laser direct writing and Raman Stokes contrast screening of quantum emitter sites in hBN.

Discover nano·2026

Same author

A Label-Free Hyperspectral Imaging Device for Ex Vivo Characterization and Grading of Meningioma Tissues.

Journal of biophotonics·2025

Same author

Myelinated fiber labeling and orientation mapping of the human brain with light-sheet fluorescence microscopy.

NeuroImage·2025

Same author

Quantitative cytoarchitectural phenotyping of deparaffinized human brain tissues.

Communications biology·2025

Same author

Anisotropic light propagation in human brain white matter.

Neurophotonics·2025

Search research articles

Related Experiment Video

Updated: Jun 19, 2026

Studying DNA Looping by Single-Molecule FRET

Studying DNA Looping by Single-Molecule FRET

Published on: June 28, 2014

Tetramer opening in LacI-mediated DNA looping.

Danielis Rutkauskas¹, Hongli Zhan, Kathleen S Matthews

¹European Laboratory for Nonlinear Spectroscopy and Department of Physics, University of Florence, 50019 Sesto Fiorentino (FI), Italy.

Proceedings of the National Academy of Sciences of the United States of America

|October 7, 2009

Summary

The lactose repressor protein (LacI) forms DNA loops essential for gene regulation. Protein opening influences loop structure, with cross-linking experiments revealing specific roles for different LacI conformations in DNA looping.

More Related Videos

CRISPR-Mediated Reorganization of Chromatin Loop Structure

CRISPR-Mediated Reorganization of Chromatin Loop Structure

Published on: September 14, 2018

Related Experiment Videos

Last Updated: Jun 19, 2026

Studying DNA Looping by Single-Molecule FRET

Studying DNA Looping by Single-Molecule FRET

Published on: June 28, 2014

CRISPR-Mediated Reorganization of Chromatin Loop Structure

CRISPR-Mediated Reorganization of Chromatin Loop Structure

Published on: September 14, 2018

Area of Science:

Molecular Biology
Biophysics
Genetics

Background:

The lactose repressor protein (LacI) regulates gene transcription in bacteria by binding DNA operators.
Efficient LacI regulation requires simultaneous binding to two operators, forming a DNA loop.
Previous studies proposed various DNA loop structures and LacI conformations.

Purpose of the Study:

To investigate the role of protein opening in LacI-mediated DNA loop formation.
To analyze how LacI structural conformations affect DNA looping dynamics.

Main Methods:

Utilized single-molecule tethered particle motion (TPM) assays.
Employed LacI protein mutants chemically cross-linked at specific positions.
Analyzed wild-type and uncross-linked LacI mutants.

Main Results:

Observed two distinct DNA looping structures in wild-type and uncross-linked LacI.
Cross-linking at the N-terminal DNA binding head (E36C) abolished DNA looping.
Cross-linking near the C-terminal tetramerization domain (Q231C) altered looping geometry.

Conclusions:

Tetramer opening is crucial for specific LacI/DNA loop conformations.
Protein flexibility influences the ability and geometry of DNA looping.
LacI structural dynamics are integral to its regulatory function.