Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Twin molecular scissors link creation of microRNAs with gene-silencing

04.11.2005


New insights into vital genome regulation strategy provided



One of the body’s primary strategies for regulating its genome is a kind of targeted gene silencing orchestrated by small molecules called microRNAs, or miRNAs. First observed only a few years ago, these molecules appear to inactivate messenger RNA, itself responsible for translating genes into proteins. Scientists have been eager to know more about miRNAs, clearly important players on the genetic field despite having gone unnoticed for so long. How are they produced? And how do they work?

In a series of studies published over the past year, a research team at The Wistar Institute has provided considerable insight into the world of miRNAs. In their first study, which appeared last year in Nature, they identified a two-protein complex, called the microprocessor, which controls the earliest steps in the creation of miRNAs in the cell nucleus. In their next study, published in Nature earlier this year, the Wistar group described a three-protein complex that picks up the process in the cell cytoplasm and carries it through to the maturation of the finished miRNAs.


Now, in new findings published online November 3 in Cell, Wistar professor Ramin Shiekhattar, Ph.D., and his colleagues report that the three-protein complex has been identified as RISC, a previously glimpsed but ill-defined molecular complex known to be involved in gene silencing. RISC, the new study demonstrates, not only oversees production of miRNAs, as described in the earlier study this year, but is also responsible for miRNA specificity in silencing particular messenger RNAs.

In RISC, two of the three components, Dicer and Argonaute 2, are enzymes bound together by the third member, TRBP. Dicer cuts double-stranded precursor molecules shaped like hairpins into pairs of short single-stranded miRNAs – in essence, nipping off the bend in the pin. RISC then unzips the two single-stranded miRNAs from each other and identifies and holds one as a guide to help it find the specific messenger RNA to be inactivated. Using complementarity to match the guide miRNA to a particular length of its target messenger RNA, Dicer and TRBP then hand over the messenger RNA for cutting by Argonaute 2. Still holding the guide miRNA, RISC then scouts for additional copies of its target messenger RNA to cut. The cutting destroys the messenger RNA, effectively silencing the gene from which it was transcribed.

"The two enzymes in the complex are like two scissors working together in a concerted fashion, connected and coordinated by the third member of the complex," Shiekhattar explains.

Another scientific question surrounding RISC was also resolved by the current study. Some investigators had theorized that the activity of RISC required ATP for energy. ATP, or adenosine triphosphate, is a molecule used to store and release energy for tasks throughout the body.

"The work of RISC is being accomplished with no energy requirement whatsoever," Shiekhattar says. "All of the activity – the separation of the strands, the multiple cutting steps, everything – is being done in the absence of any energy use."

Instead, he says, the different molecules involved have stronger and weaker affinities for each other that govern their stepwise associations and disassociations as the process unfolds.

Franklin Hoke | EurekAlert!
Further information:
http://www.wistar.org

More articles from Life Sciences:

nachricht Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH

nachricht Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>