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Related Concept Videos

The Replisome03:01

The Replisome

DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
The Replisome03:01

The Replisome

DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...
The DNA Replication Fork01:02

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 Fork01:02

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...
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...
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...

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Related Experiment Video

Updated: Jul 13, 2026

Strand-Specific Analysis of Proteins at Replicating DNA Strands by Enrichment and Sequencing of Protein-Associated Nascent DNA Method
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Strand-Specific Analysis of Proteins at Replicating DNA Strands by Enrichment and Sequencing of Protein-Associated Nascent DNA Method

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Dynamic DNA helicase-DNA polymerase interactions assure processive replication fork movement.

Samir M Hamdan1, Donald E Johnson, Nathan A Tanner

  • 1Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.

Molecular Cell
|August 21, 2007
PubMed
Summary

Bacteriophage T7 DNA polymerase and helicase maintain high processivity through dynamic interactions. A high-affinity site facilitates synthesis, while electrostatic binding allows polymerase to remain tethered to the helicase during dissociation.

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Strand-Specific Analysis of Proteins at Replicating DNA Strands by Enrichment and Sequencing of Protein-Associated Nascent DNA Method
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Strand-Specific Analysis of Proteins at Replicating DNA Strands by Enrichment and Sequencing of Protein-Associated Nascent DNA Method

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Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase
07:27

Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase

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Visualizing Single-molecule DNA Replication with Fluorescence Microscopy
15:57

Visualizing Single-molecule DNA Replication with Fluorescence Microscopy

Published on: October 9, 2009

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Virology

Background:

  • Bacteriophage T7 DNA polymerase and helicase are essential for DNA replication.
  • Understanding their interaction is key to comprehending DNA replication dynamics.

Purpose of the Study:

  • To elucidate the mechanism of dynamic processivity in bacteriophage T7 DNA replication.
  • To investigate the interaction modes between DNA polymerase and DNA helicase.

Main Methods:

  • Ensemble and single-molecule techniques were employed.
  • Analysis of DNA polymerase-helicase interactions during DNA synthesis.

Main Results:

  • The DNA polymerase and helicase exhibit dynamic processivity exceeding 17,000 nucleotides.
  • Two interaction modes were identified: a high-affinity binding site for synthesis and an electrostatic binding mode.
  • The polymerase transiently dissociates from DNA every ~5000 bases but remains bound to the helicase via electrostatic interactions.

Conclusions:

  • Dynamic processivity is achieved through a dual-mode interaction system between the DNA polymerase and helicase.
  • The electrostatic interaction allows the polymerase to remain associated with the replisome during dissociation events, facilitating primer-template searching.