Helicase and Topoisomerase | DNA Replication | English Subtitles | Lecture 8 | Dr. Muhammad Naveed

DNA Helicase and DNA Topoisomerase:
DNA helicase plays a crucial role in the process of DNA replication. During replication, the DNA double helix needs to be unwound so that the genetic information can be copied. This is where DNA helicase comes in.
The helicase enzyme works by breaking the hydrogen bonds between the two DNA strands, causing the double helix to separate and form a replication fork. This separation generates single-stranded DNA templates that can be used by other enzymes, such as DNA polymerase, to synthesize new complementary strands.
DNA helicase moves along the DNA molecule, separating the strands ahead of the replication machinery. It uses energy from ATP hydrolysis to power its unwinding activity, moving in a direction that allows the replication process to continue efficiently.
In summary, DNA helicase is pivotal in DNA replication as it unwinds the double helix, creating the necessary single-stranded DNA templates for the replication machinery to accurately synthesize new DNA strands.
DNA Topoisomerase:
DNA topoisomerases are enzymes that manage the topological changes in DNA during processes like replication, transcription, recombination, and repair. They play a crucial role in relieving the tension generated by DNA unwinding during replication. There are two main types: topoisomerase I and topoisomerase II.
Topoisomerase I: This enzyme works by creating a transient break in one strand of the DNA double helix, allowing the other strand to rotate around the break to relieve torsional stress. Once the rotation occurs, the broken DNA strand is rejoined. This action resolves the supercoiling generated ahead of the replication fork during DNA unwinding.
Topoisomerase II: Unlike topoisomerase I, topoisomerase II creates a transient break in both strands of the DNA double helix. It is crucial for untangling DNA that has undergone more complex structural changes, such as knots and interlinked DNA molecules. Topoisomerase II is particularly important during replication and is often referred to as DNA gyrase in prokaryotes.
During DNA replication, the action of helicases creates torsional stress ahead of the replication fork by unwinding the DNA. This stress could impede the progress of the replication machinery if left unchecked. Here, topoisomerases come into play to alleviate this stress by relaxing the supercoils and knots that form ahead of the replication fork. By briefly cutting the DNA strands, allowing them to swivel, and then resealing the breaks, topoisomerases help maintain the integrity of the DNA molecule during replication.
Without the action of DNA topoisomerases, DNA replication would be hindered due to the buildup of torsional stress, leading to structural problems in the DNA molecule and potential disruptions in the replication process.
About Dr. Muhammad Naveed
(HoD, Biotechnology, University of Central Punjab, Lahore)
With distinction, Dr. Muhammad Naveed obtained a Ph.D. degree in Biotechnology (Genomics & Bioinformatics) from Quaid-e-Azam University, Islamabad. He has won Ph.D. indigenous & IRSIP scholarships from HEC. He has done Pre-Doc research at the University of Ghent, Belgium. HEC awarded him the best Ph.D. (IRSIP) Scholar of the Year in 2013 & QAU honored him as a “Distinguished Alumni” in 2017. He is doing research projects in Bioinformatics, Molecular Biotechnology and vaccine designing, and Drug designing against infectious diseases. He has supervised 90 MSc. and 78 MPhil. & 01 Ph.D. students. He has published 140 Research articles with 1106 impact factors, 5160 citations, 01 book, 03 book chapters, and filed 05 Patents. He was awarded the distinguished “Researcher of the Year” in 2016 (UoG) and 2018, 2019 & 2021 (UCP).
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