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 Russian scientists show changes in the erythrocyte nanostructure under stress
22.02.2019 | Lobachevsky University

nachricht How the intestinal fungus Candida albicans shapes our immune system
22.02.2019 | Exzellenzcluster Präzisionsmedizin für chronische Entzündungserkrankungen

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: (Re)solving the jet/cocoon riddle of a gravitational wave event

An international research team including astronomers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has combined radio telescopes from five continents to prove the existence of a narrow stream of material, a so-called jet, emerging from the only gravitational wave event involving two neutron stars observed so far. With its high sensitivity and excellent performance, the 100-m radio telescope in Effelsberg played an important role in the observations.

In August 2017, two neutron stars were observed colliding, producing gravitational waves that were detected by the American LIGO and European Virgo detectors....

Im Focus: Light from a roll – hybrid OLED creates innovative and functional luminous surfaces

Up to now, OLEDs have been used exclusively as a novel lighting technology for use in luminaires and lamps. However, flexible organic technology can offer much more: as an active lighting surface, it can be combined with a wide variety of materials, not just to modify but to revolutionize the functionality and design of countless existing products. To exemplify this, the Fraunhofer FEP together with the company EMDE development of light GmbH will be presenting hybrid flexible OLEDs integrated into textile designs within the EU-funded project PI-SCALE for the first time at LOPEC (March 19-21, 2019 in Munich, Germany) as examples of some of the many possible applications.

The Fraunhofer FEP, a provider of research and development services in the field of organic electronics, has long been involved in the development of...

Im Focus: Regensburg physicists watch electron transfer in a single molecule

For the first time, an international team of scientists based in Regensburg, Germany, has recorded the orbitals of single molecules in different charge states in a novel type of microscopy. The research findings are published under the title “Mapping orbital changes upon electron transfer with tunneling microscopy on insulators” in the prestigious journal “Nature”.

The building blocks of matter surrounding us are atoms and molecules. The properties of that matter, however, are often not set by these building blocks...

Im Focus: University of Konstanz gains new insights into the recent development of the human immune system

Scientists at the University of Konstanz identify fierce competition between the human immune system and bacterial pathogens

Cell biologists from the University of Konstanz shed light on a recent evolutionary process in the human immune system and publish their findings in the...

Im Focus: Transformation through Light

Laser physicists have taken snapshots of carbon molecules C₆₀ showing how they transform in intense infrared light

When carbon molecules C₆₀ are exposed to an intense infrared light, they change their ball-like structure to a more elongated version. This has now been...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Global Legal Hackathon at HAW Hamburg

11.02.2019 | Event News

The world of quantum chemistry meets in Heidelberg

30.01.2019 | Event News

Our digital society in 2040

16.01.2019 | Event News

 
Latest News

JILA researchers make coldest quantum gas of molecules

22.02.2019 | Physics and Astronomy

Understanding high efficiency of deep ultraviolet LEDs

22.02.2019 | Materials Sciences

Russian scientists show changes in the erythrocyte nanostructure under stress

22.02.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>