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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...
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...
Restarting Stalled Replication Forks02:37

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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...
The DNA Replication Fork01:02

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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

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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...

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DNA replication requires coordinated unwinding. Optical tweezers revealed Phi29 DNA polymerase couples replication and unwinding, using similar mechanisms despite sequence and tension variations.

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Area of Science:

  • Molecular Biology
  • Biophysics
  • Biochemistry

Background:

  • DNA duplication necessitates precise coordination between replication and unwinding.
  • Understanding the interplay between these processes at the single-molecule level is crucial for comprehending DNA metabolism.

Purpose of the Study:

  • To investigate the coupling dynamics between DNA replication and unwinding by individual Phi29 DNA polymerase molecules.
  • To examine how mechanical tension and DNA sequence affect these coupled activities.

Main Methods:

  • Utilized optical tweezers to apply mechanical tension and monitor single Phi29 DNA polymerase molecules.
  • Employed a double-stranded DNA (dsDNA) hairpin substrate for simultaneous replication and unwinding assays.
  • Compared wild-type and unwinding-deficient Phi29 DNA polymerase variants.

Main Results:

  • Both mechanical tension and DNA sequence differentially modulated replication rates, unwinding rates, and pause kinetics for the polymerase variants.
  • Pause kinetics analysis, when incorporated into a model, indicated that both polymerase types actively destabilize the replication fork.
  • Both wild-type and mutant polymerases employ a similar active mechanism for fork destabilization.

Conclusions:

  • Phi29 DNA polymerase couples DNA replication and unwinding through a conserved active mechanism, irrespective of sequence or applied tension.
  • Insights into the topological strategies for coupling replication and unwinding in Phi29 DNA polymerase and other systems were gained.