Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Essential cell division ’zipper’ anchors to so-called junk DNA

29.08.2002


Mechanism may provide insights into development and cancer



When cells divide in two, they must carefully manage the process by which their DNA is replicated and then apportioned to the daughter cells. In one critical step along the way, the replicated DNA strands - or sisters - are held together for a period by a temporary scaffold of bridging proteins. When the timing is right, the proteins unzip, allowing the DNA sisters to separate. Errors in this or other steps in cell division can lead to cell death, faulty development, or cancer, which is largely defined as misregulated cell division.

Scientists have had a number of questions about these important bridging proteins, called cohesins. For example, how and where do the proteins attach themselves to the DNA? To protect genes from inappropriate activation, DNA is tightly wrapped around small proteins called histones and then further coiled into a higher structure called chromatin that serves as an effective accessibility barrier to the genes.


In a new study in the August 29 issue of Nature, researchers at The Wistar Institute identify a cohesin-containing protein complex that reshapes chromatin to allow cohesins to bind to DNA. In doing so, they also identified the locations on the human genome where the cohesins bind. Somewhat to their surprise, the binding sites were found to be a repetitive DNA sequence found throughout the human genome for which no previous role had ever been identified. These bits of DNA, known as Alu sequences, are liberally represented along those vast stretches of the human genome not known to directly control genetic activity, sometimes referred to as junk DNA.

"One thing that interested us is that there are 500 thousand to 1 million Alu repeats across the human genome," says Ramin Shiekhattar, Ph.D., an associate professor at The Wistar Institute and senior author on the Nature study. "These sequences are very common. And this makes sense if one of their roles is to bind to the bridging proteins, the cohesins, to keep the replicated DNA sisters together until it is time for them to separate. Multiple bridging sites throughout the DNA would be needed for this system to work. They couldn’t be unique sequences."

In their investigations, Shiekhattar and his coworkers noticed that many, but not all the Alu sequences bound cohesin, and they wondered what rules might govern the process. Additional experiments revealed that if the histone proteins were methylated and acetylated - that is, if a methyl and acetyl molecule were bound to them - then the chromatin structure relaxed to allow access to the DNA. But if the Alu sequence on the DNA was itself methylated, then the cohesin could not bind to the DNA at that site.

Why these modifications might take place at some Alu sites and not others was not clear. But, taken together, the research team’s observations are supportive of the existence of what some scientists have termed a "histone code." This recently proposed theory suggests that a system of complex, interdependent modifications to histones is responsible for regulating access to DNA and genes.

"The idea that a kind of code of modifications to the molecular packaging of DNA may govern gene activity is an intriguing one," Shiekhattar says. "If we were to better understand this code, it might provide us with important insights into diseases tied to problems in gene control, including developmental disorders and cancer. These are some of the questions we’re looking into now, using this study as a starting point."

Franklin Hoke | EurekAlert!

More articles from Life Sciences:

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

nachricht Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Transport of molecular motors into cilia

28.03.2017 | Life Sciences

A novel hybrid UAV that may change the way people operate drones

28.03.2017 | Information Technology

NASA spacecraft investigate clues in radiation belts

28.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>