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 At last, butterflies get a bigger, better evolutionary tree
16.02.2018 | Florida Museum of Natural History

nachricht New treatment strategies for chronic kidney disease from the animal kingdom
16.02.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>