Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Normal chromosome ends elicit a limited DNA damage response

24.11.2005


Researchers at the Salk Institute for Biological Studies discovered that cells co-opted the machinery that usually repairs broken strands of DNA to protect the integrity of chromosomes. This finding solves for the first time an important question that has long puzzled scientists.



The natural ends of chromosomes look just like broken strands of DNA that a cell’s repair machinery is designed to fix. But mending chromosome ends, or telomeres, would set the stage for the development of cancer in successive generation of cells.

To prevent the cell’s DNA repair machinery from confusing telomeres with broken strands of DNA that need to be repaired, the tips of chromosomes are tucked in and shielded by a phalanx of proteins, forming a protective "cap".


Ironically, to form this protective structure at the end of chromosomes, nature solicited help from the very same repair machinery whose misguided repair attempts the cap is supposed to hold at bay, reports the Salk team, led by Jan Karlseder, in the current issue of Molecular Cell.

Scientists had long surmised that the protective telomere-protein complex had to unravel when enzymes need to gain access in order to copy the chromosome’s DNA in preparation for cell division. And if so, they wondered, why didn’t the presumably exposed chromosome ends trigger a DNA damage response?

Turns out they do, at least to a limited extend.

"During a small window right after DNA replication, when the cell gets ready for cell division, chromosome ends are exposed," says research fellow and first author Ramiro Verdun who emphasizes that, "it would be very unhealthy for the cell if it happened at any other time."

In addition, Verdun and his colleagues found that several well-known members of the DNA damage response machinery – recruited by the now unprotected telomeres - congregate at the tips of chromosomes.

"We believe that the localization of repair proteins to chromosome ends, and detection of telomeres as damage at this precise time are necessary to trigger the re-formation of a protective telomeric structure," says Karlseder, an assistant professor in the Regulatory Biology Laboratory.

In contrast to damaged strands of DNA, they hypothesize, the repair process never gets fully underway at telomeres. Instead, the very tips of the chromosomes are looped back, tucked in and covered with telomeric proteins.

"The cell tries to fix everything to make sure that the genetic information is safe and complete for the next generation of cells," says Verdun. "But in the case of healthy chromosome tips or telomeres, repair would have disastrous consequences," he adds.

Repairing telomeres would randomly fuse whole chromosomes end-to-end. During the next cell division the sorting mechanism, which ensures that each daughter cell receives a full complement of chromosomes would inevitably rip the fused chromosomes apart.

"Such fusion breakage cycles scramble the genome over time, and cause genome instability, which is a hallmark of cancer cells," explains Karlseder. "This demonstrates the importance of telomeres in preserving genome integrity and preventing cancer development."

Cathy Yarbrough | EurekAlert!
Further information:
http://www.salk.edu

More articles from Life Sciences:

nachricht Flow of cerebrospinal fluid regulates neural stem cell division
22.05.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Chemists at FAU successfully demonstrate imine hydrogenation with inexpensive main group metal
22.05.2018 | Friedrich-Alexander-Universität Erlangen-Nürnberg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>