Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Spying on a Cellular Director in the Cutting Room

24.03.2010
Like a film director cutting out extraneous footage to create a blockbuster, the cellular machine called the spliceosome snips out unwanted stretches of genetic material and joins the remaining pieces to fashion a template for protein production.

But more than box office revenues are at stake: if the spliceosome makes a careless cut, disease likely results.

Using a new approach to studying the spliceosome, a team led by University of Michigan chemistry and biophysics professor Nils Walter, collaborating closely with a team led by internationally recognized splicing experts John Abelson and Christine Guthrie of the University of California, San Francisco, spied on the splicing process in single molecules.

The research is scheduled to be published online March 21 in Nature Structural and Molecular Biology.

Since its Nobel Prize-winning discovery in 1977, gene splicing has been studied in a number of organisms, including yeast and human cells, using both genetic and biochemical approaches. While these methods can yield snapshots, they can't monitor the ongoing process. The new study, which utilizes a technique called fluorescence resonance energy transfer (FRET) and a sophisticated microscope that watches single molecules in action, allows researchers to observe in real time the contortions involved in spliceosome assembly and operation.

By molecular-scale standards, the spliceosome is a monster of a machine, made up of five RNA and 100 or more protein subunits that agilely assemble, step-by-step, into the giant complex when it's time to carry out its work.

True to the movie director analogy, the spliceosome not only wields the scissors, it's also "the brain that decides where to cut," Walter said. The "footage" it works on is the genetic material contained in RNA molecules.RNA carries coded instructions for producing the proteins our body needs for building and repairing tissues, regulating body processes and many other sections called introns. The spliceosome's task is to recognize and excise introns. Once the introns are removed, the spliceosome can stitch together exons in various combinations. Thanks to this mixing and matching of exons, a relatively small number of genes (a little over 20,000 in humans) can serve as blueprints for a great variety of proteins.

Walter and colleagues spied on the splicing process by attaching fluorescent tags to exons on either side of an intron in a short section of RNA they designed specifically for such studies. When laser light is shined on the tags, FRET can detect how close together or far apart the exons are. Repeated observations over time result in a molecular-scale "movie" that reveals how parts of the RNA molecule wiggle around, both before and during splicing.

The researchers first studied the RNA in the absence of the spliceosome. "Conventional wisdom has been that the spliceosome directs the whole splicing process, that the RNA itself has little influence on it," Walter said. "But we saw the RNA molecule flexing on its own, with the intron folding and unfolding in a way that brings the exons closer together, suggesting a more active role for introns."

When the team added an extract containing spliceosome components, along with ATP---the energy currency that fuels spliceosome assembly---the distance between exons first increased, then decreased even more, and splicing occurred. Interestingly, the series of contortions that RNA went through during splicing was not a one-way path; the steps were reversible.

"Imagine the movie director having doubts about what scenes to cut and continuously going back and forth in holding different pieces of footage together before actually making a decision and splicing the film. That's what we saw happening at the molecular level," Walter said. "To our knowledge, our data provide the first direct glimpse of such reversible conformational changes during the splicing process."

Next, the researchers plan to attach fluorescent tags to different parts of the system to see how the various parts relate to one another in space and time during splicing. The eventual goal is to construct a comprehensive model showing how RNA and the spliceosome can so faithfully interact throughout the splicing process to avoid the onset of disease.

Walter's coauthors on the paper are U-M graduate students Mario Blanco, Franklin Fuller and Pavithra Aravamudhan; former graduate student Mark Ditzler; former undergraduate student Mona Wood; and Abelson, Guthrie, Tommaso Villa, Daniel Ryan, Jeffrey Pleiss and Corina Maeder of the University of California, San Francisco.

The research was funded by the National Institutes of Health, the American Cancer Society, the Agouron Institute and the U-M Rackham Graduate School.

For more information:

Nils Walter, visit: www.chem.lsa.umich.edu/chem/faculty/facultyDetail.php?Uniqname=nwalter

Nature Structural and Molecular Biology: www.nature.com/nsmb/

Nancy Ross-Flanigan | Newswise Science News
Further information:
http://www.nature.com/nsmb/
http://www.umich.edu

More articles from Life Sciences:

nachricht Decoding the genome's cryptic language
27.02.2017 | University of California - San Diego

nachricht New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New pop-up strategy inspired by cuts, not folds

27.02.2017 | Materials Sciences

Sandia uses confined nanoparticles to improve hydrogen storage materials performance

27.02.2017 | Interdisciplinary Research

Decoding the genome's cryptic language

27.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>