Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sisyphean movement of motor proteins may help preserve DNA integrity

27.10.2005


Researchers studying how proteins called helicases travel along strands of DNA have found that when the proteins hit an obstacle they snap back to where they began, repeating the process over and over, possibly playing a preventative role in keeping the genome intact.


A helicase (blue) moves rapidly on a highly flexible DNA track. Such movement may prevent the accumulation of toxic proteins on the DNA. Graphic courtesy Taekjip Ha



Taekjip Ha, a professor of physics at the University of Illinois at Urbana-Champaign and a Howard Hughes Medical Institute investigator, likens the biological scenario to Boston Red Sox baseball; the team rolls along only to hit a late-season obstacle called the New York Yankees. Then, like the always-anticipated annual cry from Chicago Cubs fan, it’s back to square one next year.

However, instead of causing more misery, as is the case for a baseball fan, this motor protein’s starting over may serve a beneficial purpose, clearing other, undesired proteins from the DNA, Ha said. The research was done in vitro, using purified proteins and studied with a technique that visualizes individual molecules on DNA. Whether the scenario plays out in real cells in not known and under exploration.


The discovery appears in the Oct. 27 issue of the journal Nature, along with a separate "News & Views" article by Eckhard Jankowsky, a biochemist at the Center for RNA Molecular Biology in Case Western University’s School of Medicine, who wrote about the potential importance of the findings.

Ha’s postdoctoral fellow Sua Myong led the study, looking at the Rep helicase from an E-coli bacterium. Rep is known to be involved in restarting DNA replication stalled by DNA damage. As a single protein, a monomer, Rep can travel one way along a single strand of DNA but by itself cannot unzip it. Rep’s progress was visualized using the single molecule fluorescence resonance energy transfer (FRET) technique that Ha had developed.

By tagging the protein and DNA with green and red dyes, Myong measured FRET changes as Rep traveled along single DNA strands, which are short segments extending out from double strands. Each time the protein reached either the junction of the full double-stranded DNA or hit an artificially created protein obstacle, Rep instantly returned to near the beginning of the single strand on which it had initially bound.

Upon closer examination using FRET, researchers discovered that Rep’s configuration gradually closed as it reached the obstacle in its path. Then, conformational changes of Rep allow it to grab and transfer to the end of the single-stranded DNA, leading to the next cycle.

"Although the very flexible single strand of DNA likely bombards the protein constantly, the protein doesn’t seem to pay attention to this overture until it hits a physical blockade," Ha said.

Researchers had theorized that obstacles would force motor proteins to disengage from DNA. "The finding was totally unexpected and may indicate a new function for the protein," Ha said. Jankowsky wrote that scientists "should not immediately search for the helix that the enzyme unzips, but instead remember how Rep snaps back."

In cells, single strands of DNA often occur when something is wrong, Ha said. The recycling action, he said, may represent a desirable function of the protein by keeping it engaged on a single strand, allowing time for repairs that allow normal DNA replication.

The human body has more than 200 types of helicases involved in replication, transcription, repair and other genetic processes, Ha said. Defective helicases have been linked to increased cancer risks and premature aging.

Co-authors with Myong and Ha were Ivan Rasnik, a former postdoctoral fellow who now is a professor of physics at Emory University in Atlanta; Chirlmin Joo, a doctoral student in Ha’s lab; and Timothy M. Lohman, a professor of biochemistry and molecular biophysics at the Washington University School of Medicine in St. Louis.

Jim Barlow | EurekAlert!
Further information:
http://www.uiuc.edu

More articles from Life Sciences:

nachricht The birth of a new protein
20.10.2017 | University of Arizona

nachricht Building New Moss Factories
20.10.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>