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Related Concept Videos

DNA Helicases00:55

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...
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...
Mismatch Repair01:20

Mismatch Repair

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the new strand and replacing the erroneous bases with correct nucleotides. Mismatch repair is coordinated by many proteins in both prokaryotes and eukaryotes.
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
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...
DNA Topoisomerases02:02

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...
Conservative Site-specific Recombination and Phase Variation02:53

Conservative Site-specific Recombination and Phase Variation

Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...

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Related Experiment Video

Updated: Jul 3, 2026

Hybrid Ensemble and Single-molecule Assay to Image the Motion of Fully Reconstituted CMG
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Hybrid Ensemble and Single-molecule Assay to Image the Motion of Fully Reconstituted CMG

Published on: July 26, 2024

The Mcm2-7 complex has in vitro helicase activity.

Matthew L Bochman1, Anthony Schwacha

  • 1Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.

Molecular Cell
|July 29, 2008
PubMed
Summary

The eukaryotic replicative helicase, Mcm2-7, unwinds DNA, contrary to prior in vitro studies. This activity is regulated by an ATP-dependent Mcm2/5 gate, crucial for DNA replication fork progression.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • Eukaryotic DNA replication relies on helicases to unwind DNA at the replication fork.
  • The precise identity and function of the eukaryotic replicative helicase, particularly the Mcm2-7 complex, remain debated.
  • In vitro studies suggest only a subset (Mcm467) unwinds DNA, conflicting with in vivo evidence implicating the full Mcm2-7 complex.

Purpose of the Study:

  • To resolve the discrepancy regarding the helicase activity of the Mcm2-7 complex versus Mcm467.
  • To investigate the role of the Mcm2/5 interface in regulating Mcm2-7 helicase function.
  • To identify conditions that restore Mcm2-7 helicase activity.

Main Methods:

  • Comparative analysis of Mcm2-7 and Mcm467 DNA binding and unwinding kinetics.

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Last Updated: Jul 3, 2026

Hybrid Ensemble and Single-molecule Assay to Image the Motion of Fully Reconstituted CMG
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Hybrid Ensemble and Single-molecule Assay to Image the Motion of Fully Reconstituted CMG

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Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase
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Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase

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02:44

Isolating Interaction-Null/Impaired Mutants Using the Yeast Two-Hybrid Assay

Published on: December 29, 2023

  • Investigation of the Mcm2/5 interface's role in helicase regulation.
  • Assessing the impact of reaction conditions, including anion dependence, on helicase activity.

    • Main Results:

    • Mcm2-7 and Mcm467 exhibit distinct single-stranded DNA association rates and circular DNA binding capabilities.
    • The Mcm2/5 interface acts as a hypothesized ATP-dependent "gate" controlling Mcm2-7 activity.
    • Specific reaction conditions that "close" the Mcm2-7 gate restore helicase activity, which is strongly anion-dependent.

    Conclusions:

    • Purified Mcm2-7 complex possesses helicase activity, confirming its role in DNA replication.
    • Functional evidence supports the existence of an Mcm2/5 gate regulating Mcm2-7 helicase function.
    • These findings provide a foundation for further mechanistic studies of the eukaryotic replicative helicase.