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Related Concept Videos

Restarting Stalled Replication Forks02:37

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 Recombination02:31

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...
Disassembly of Intermediate Filaments01:35

Disassembly of Intermediate Filaments

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Formation of Intermediate Filaments00:57

Formation of Intermediate Filaments

Intermediate filaments are cytoskeletal proteins with higher tensile strength and flexibility than microfilaments and microtubules. Unlike the other two cytoskeletal proteins, intermediate filament formation lacks the enzymatic activity to hydrolyze nucleotides like ATP and GTP to generate energy for polymerization. Therefore, the formation of intermediate filaments is multistep self-assembly. The involvement of any accessory proteins in intermediate filament formation has not yet been reported.
The Structure of Intermediate Filaments01:19

The Structure of Intermediate Filaments

The intermediate filaments are one of three widely studied cytoskeletal filaments. They are so named as their diameter (10 nm) is in between that of microfilaments (7 nm) and the microtubules (25 nm).  These filaments are highly stable and can remain intact when exposed to high salt concentrations and detergents. These filaments are responsible for providing stability and mechanical support to the cells. They also help in cell adhesion and maintaining tissue integrity.
Intermediate filaments...
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Fixing Double-strand Breaks

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Related Experiment Video

Updated: Jun 21, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
06:24

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51

Published on: February 13, 2019

Structural transitions within human Rad51 nucleoprotein filaments.

Ragan B Robertson1, Dana N Moses, YoungHo Kwon

  • 1Department of Biological Sciences and Biochemistry, Columbia University, 650 West 168th Street, New York, NY 10032, USA.

Proceedings of the National Academy of Sciences of the United States of America
|July 23, 2009
PubMed
Summary

Human Rad51 protein undergoes reversible structural changes during DNA strand invasion, transitioning between elongated and compressed filaments. ATP hydrolysis drives this transition, crucial for homologous recombination dynamics.

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Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae
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Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae

Published on: September 11, 2022

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Last Updated: Jun 21, 2026

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
06:24

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51

Published on: February 13, 2019

Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae
07:55

Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae

Published on: September 11, 2022

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • Rad51 is essential for homologous recombination in eukaryotes.
  • Rad51 forms various oligomeric structures, including filaments, on DNA.
  • The transition dynamics between these structures are not fully understood.

Purpose of the Study:

  • To investigate the structural transitions of human Rad51 on double-stranded DNA.
  • To determine the role of ATP hydrolysis in Rad51 filament dynamics.
  • To understand the reversibility of Rad51 structural changes.

Main Methods:

  • Single-molecule microscopy was employed to observe human Rad51 behavior on DNA.
  • Experiments utilized ATP and non-hydrolyzable ATP analogs (AMP-PNP).
  • Mutant Rad51 deficient in ATP hydrolysis was also studied.

Main Results:

  • Human Rad51 forms elongated filaments on DNA, which shorten upon ATP hydrolysis.
  • Compressed filaments can reversibly elongate with ATP or AMP-PNP.
  • Rad51 mutants or wild-type Rad51 with AMP-PNP were locked in elongated states, resisting dissociation.

Conclusions:

  • Nucleotide hydrolysis by human Rad51 triggers reversible structural transitions between filament states.
  • ATP hydrolysis is key for filament compression and subsequent dissociation.
  • Understanding these dynamics is vital for homologous recombination mechanisms.