Related Experiment Video
Updated: Aug 6, 2026
07:37
Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase
Published on: September 27, 2024
Unwinding of forked DNA structures by UvrD
Chris J Cadman1, Steven W Matson, Peter McGlynn
1School of Medical Sciences, Institute of Medical Sciences University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
Journal of Molecular Biology
|August 8, 2006
Summary
The UvrD helicase unwinds forked DNA structures by initiating unwinding from backbone discontinuities. This activity suggests UvrD targets replication and recombination intermediates, potentially with redundant functions to Rep in replication restart.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Genome duplication relies on processing blocked replication forks.
- UvrD helicase in Escherichia coli is involved in processing damaged replication forks and recombination intermediates.
Purpose of the Study:
- To investigate the DNA unwinding capabilities of UvrD helicase on forked DNA structures.
- To determine if UvrD can target DNA intermediates crucial for replication and recombination.
Main Methods:
- In vitro assays to assess UvrD helicase activity on various forked DNA substrates.
- Analysis of UvrD's unwinding polarity and substrate preference.
Main Results:
- UvrD helicase unwinds forked DNA structures by initiating unwinding from phosphodiester backbone discontinuities.
- UvrD demonstrates a substrate preference for fork structures with a nascent lagging strand.
- UvrD's unwinding polarity shifts to favor lagging strand unwinding on specific substrates.
Conclusions:
- UvrD helicase possesses the capacity to target DNA intermediates involved in replication and recombination.
- UvrD's activity on specific fork structures resembles the PriC-Rep pathway, suggesting functional redundancy with Rep in replication restart.
Related Concept Videos
02:37Restarting 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...
02:37Restarting 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...
01:02The 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...
01:02The 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...
02:02DNA 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...
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
02:31Homologous 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...