Research & Development World

  • R&D World Home
  • Topics
    • Aerospace
    • Automotive
    • Biotech
    • Careers
    • Chemistry
    • Environment
    • Energy
    • Life Science
    • Material Science
    • R&D Management
    • Physics
  • Technology
    • 3D Printing
    • A.I./Robotics
    • Software
    • Battery Technology
    • Controlled Environments
      • Cleanrooms
      • Graphene
      • Lasers
      • Regulations/Standards
      • Sensors
    • Imaging
    • Nanotechnology
    • Scientific Computing
      • Big Data
      • HPC/Supercomputing
      • Informatics
      • Security
    • Semiconductors
  • R&D Market Pulse
  • R&D 100
    • Call for Nominations: The 2025 R&D 100 Awards
    • R&D 100 Awards Event
    • R&D 100 Submissions
    • Winner Archive
    • Explore the 2024 R&D 100 award winners and finalists
  • Resources
    • Research Reports
    • Digital Issues
    • R&D Index
    • Subscribe
    • Video
    • Webinars
  • Global Funding Forecast
  • Top Labs
  • Advertise
  • SUBSCRIBE

Crucial step in human DNA replication observed using fluorescent tags

By R&D Editors | April 1, 2013

Stephen J. Benkovic, Mark Hedglin, and other members of Professor Benkovic's research team have studied the importance of "clamp loader" enzymes and their activities during DNA replication. In this image, the clamp loader is represented, for illustrative purposes, by a hand, which is loading the sliding clamp ring onto DNA. Image: Benkovic laboratory, Penn State UniversityFor the first time, an elusive step in the process of human DNA replication has been demystified by scientists at Penn State University. According to senior author Stephen J. Benkovic, an Evan Pugh Professor of Chemistry and holder of the Eberly Family Chair in Chemistry at Penn State, the scientists “discovered how a key step in human DNA replication is performed.” The results of the research will be published in eLife.

Part of the DNA replication process—in humans and in other life forms—involves loading of molecular structures called sliding clamps onto DNA. This crucial step in DNA replication had remained somewhat mysterious and had not been well studied in human DNA replication. Mark Hedglin, a postdoctoral researcher in Penn State’s Department of Chemistry and a member of Benkovic’s team, explains that the sliding clamp is a ring-shaped protein that acts to encircle the DNA strand, latching around it like a watch band. The sliding clamp then serves to anchor special enzymes called polymerases to the DNA, ensuring efficient copying of the genetic material. “Without a sliding clamp, polymerases can copy very few bases—the molecular ‘letters’ that make up the code of DNA—at a time. But the clamp helps the polymerase to stay in place, allowing it to copy thousands of bases before being removed from the strand of DNA,” Hedglin says.

Hedglin explains that, due to the closed circular structure of sliding clamps, another necessary step in DNA replication is the presence of a “clamp loader,” which acts to latch and unlatch the sliding clamps at key stages during the process. “The big unknown has always been how the sliding clamp and the clamp loader interact and the timing of latching and unlatching of the clamp from the DNA,” says Hedglin. “We know that polymerases and clamp loaders can’t bind the sliding clamp at the same time, so the hypothesis was that clamp loaders latched sliding clamps onto DNA, then left for some time during DNA replication, returning only to unlatch the clamps after the polymerase left so they could be recycled for further use.”

To test this hypothesis, the team of researchers used a method called Förster resonance energy transfer (FRET), a technique of attaching fluorescent “tags” to human proteins and sections of DNA in order to monitor the interactions between them. “With these tags in place, we then observed the formation of holoenzymes—the active form of the polymerase involved in DNA replication, which consists of the polymerase itself along with any accessory factors that optimize its activity,” Hedglin says. “We found that whenever a sliding clamp is loaded onto a DNA template in the absence of polymerase, the clamp loader quickly removed the clamp so that free clamps did not build up on the DNA. However, whenever a polymerase was present, it captured the sliding clamp and the clamp loader then dissociated from the DNA strand.”

The team members also found that, during the moments when both the clamp loader and the clamp were bound to the DNA, they were not intimately engaged with each other. Rather, the clamp loader released the closed clamp onto the DNA, allowing an opportunity for the polymerase to capture the clamp, completing the assembly of the holoenzyme. Subsequently, the clamp loader dissociated from DNA. “Our research demonstrates that the DNA polymerase holoenzyme in humans consists of only a clamp and a DNA polymerase. The clamp loader is not part of it. It disengages from the DNA after the polymerase binds the clamp,” Hedglin adds.

Benkovic notes that this mechanism provides a means for the cell to recycle scarce clamps when they are not in use for productive replication.

Source: Penn State University

Related Articles Read More >

Eli Lilly facility
9 R&D developments this week: Lilly builds major R&D center, Stratolaunch tests hypersonic craft, IBM chief urges AI R&D funding
professional photo of wooly mammoth in nature --ar 2:1 --personalize sq85hce --v 6.1 Job ID: 47185eaa-b213-4624-8bee-44f9e882feaa
Why science ethicists are sounding skepticism and alarm on ‘de-extinction’
ALAFIA system speeds complex molecular simulations for University of Miami drug research
3d rendered illustration of the anatomy of a cancer cell
Funding flows to obesity, oncology and immunology: 2024 sales data show where science is paying off
rd newsletter
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, trends, and strategies in Research & Development.
RD 25 Power Index

R&D World Digital Issues

Fall 2024 issue

Browse the most current issue of R&D World and back issues in an easy to use high quality format. Clip, share and download with the leading R&D magazine today.

Research & Development World
  • Subscribe to R&D World Magazine
  • Enews Sign Up
  • Contact Us
  • About Us
  • Drug Discovery & Development
  • Pharmaceutical Processing
  • Global Funding Forecast

Copyright © 2025 WTWH Media LLC. All Rights Reserved. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media
Privacy Policy | Advertising | About Us

Search R&D World

  • R&D World Home
  • Topics
    • Aerospace
    • Automotive
    • Biotech
    • Careers
    • Chemistry
    • Environment
    • Energy
    • Life Science
    • Material Science
    • R&D Management
    • Physics
  • Technology
    • 3D Printing
    • A.I./Robotics
    • Software
    • Battery Technology
    • Controlled Environments
      • Cleanrooms
      • Graphene
      • Lasers
      • Regulations/Standards
      • Sensors
    • Imaging
    • Nanotechnology
    • Scientific Computing
      • Big Data
      • HPC/Supercomputing
      • Informatics
      • Security
    • Semiconductors
  • R&D Market Pulse
  • R&D 100
    • Call for Nominations: The 2025 R&D 100 Awards
    • R&D 100 Awards Event
    • R&D 100 Submissions
    • Winner Archive
    • Explore the 2024 R&D 100 award winners and finalists
  • Resources
    • Research Reports
    • Digital Issues
    • R&D Index
    • Subscribe
    • Video
    • Webinars
  • Global Funding Forecast
  • Top Labs
  • Advertise
  • SUBSCRIBE