Related Experiment Video
Updated: Jul 12, 2026
07:37
Single-Molecule Real-Time Visualization of DNA Unwinding by CMG Helicase
Published on: September 27, 2024
Topoisomerase IIIα resolves inter- and intra-molecular intertwines during DNA replication
Biorxiv : the Preprint Server for Biology
|July 10, 2026
Summary
Topoisomerase IIIα (TOP3α) is vital for genome integrity, especially when Topoisomerase IIα (TOP2α) is impaired. TOP3α resolves DNA linkages during replication termination and when single-stranded DNA levels rise, ensuring genome stability.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Genome integrity relies on resolving topological stress.
- Vertebrate topoisomerase IIα (TOP2α) resolves catenanes during DNA replication.
- The role of Topoisomerase IIIα (TOP3α) in DNA replication is not fully understood.
Purpose of the Study:
- To investigate the role of TOP3α in DNA replication, particularly when TOP2α function is compromised.
- To determine TOP3α's substrate specificity and binding partners during replication.
Main Methods:
- Utilized Xenopus egg extracts for in vitro DNA replication studies.
- Assessed replication fork progression and daughter strand unlinking.
- Investigated TOP3α activity independently of RMI1-RMI2 and BLM helicase.
Main Results:
- TOP3α promotes replication fork progression and daughter strand unlinking during replication termination.
- TOP3α acts on lagging-strand single-stranded DNA (ssDNA) independently of known partners.
- Elevated lagging-strand ssDNA leads to intramolecular ssDNA intertwines resolved by TOP3α.
Conclusions:
- TOP3α is essential for resolving DNA topological stress during replication termination.
- TOP3α resolves both intermolecular and intramolecular DNA linkages, crucial for genome stability under various replication conditions.
More Related Videos
Related Concept Videos
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...
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...
00:55DNA 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...
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...