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Molecular Machine Turns Packaged Messenger RNA Into A Linear Transcript

Date:
February 23, 2009
Source:
Rockefeller University
Summary:
For RNA, the gateway to a productive life outside the nucleus is the nuclear pore complex, an amalgamation of 30 kinds of proteins that regulates all traffic passing through the nuclear membrane. New research shows that one of these proteins magnetically couples with a special molecule -- a helicase -- to form a machine that unpacks balled-up messenger RNA particles so that they can be translated.
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Picking from the pack. A magnetically coupled helicase (green) and nuclear pore complex protein known as Nup214 (blue) play a key role in plucking individual messenger RNA proteins from a packaged ball.
Credit: Image courtesy of Rockefeller University

For RNA, the gateway to a productive life outside the nucleus is the nuclear pore complex, an amalgamation of 30 kinds of proteins that regulates all traffic passing through the nuclear membrane. New research from Rockefeller University shows that one of these proteins magnetically couples with a special molecule — a helicase — to form a machine that unpacks balled-up messenger RNA particles so that they can be translated.

The work illuminates a previously unknown stage in the process by which genetic information is read and converted to proteins. In humans and other higher organisms, the genetic information that is encoded in the DNA is stored inside the nucleus, while the factories that convert DNA instructions into proteins are located in the surrounding cytoplasm. As those instructions — messenger RNA particles — pass through the nuclear membrane, numerous proteins that cover and protect the delicate messenger RNA molecules must be stripped off.

André Hoelz, a research associate in John D. Rockefeller Jr. Professor Günter Blobel’s Laboratory of Cell Biology, and his colleagues solved the crystal structure of a complex located on the cytoplasmic side of the nuclear pore — nucleoportin Nup214 coupled with helicase Ddx19. They then performed a series of biochemical experiments to further parse the interactions between these two molecules and to elucidate their mechanism of action.

“We found that the messenger RNA protein package and Nup214 competitively bind to the helicase, one after the other,” Hoelz notes. Each time the helicase binds the ball of messenger RNA and protein, it strips one protein molecule off. “The process is akin to a ratchet mechanism for messenger RNA export.” The result, Hoelz speculates, is a linear messenger RNA transcript that travels on to the ribosome, where it delivers instructions for building proteins.

The work may also clarify a cause underlying acute myeloid leukemia, which is associated with mutations to Nup214. “Patients with mutations in Nup214 that remove the docking site for the helicase are likely to have a messenger RNA export defect,” Hoelz says.


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The above post is reprinted from materials provided by Rockefeller University. Note: Materials may be edited for content and length.


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Rockefeller University. "Molecular Machine Turns Packaged Messenger RNA Into A Linear Transcript." ScienceDaily. ScienceDaily, 23 February 2009. <www.sciencedaily.com/releases/2009/02/090213113340.htm>.
Rockefeller University. (2009, February 23). Molecular Machine Turns Packaged Messenger RNA Into A Linear Transcript. ScienceDaily. Retrieved July 7, 2015 from www.sciencedaily.com/releases/2009/02/090213113340.htm
Rockefeller University. "Molecular Machine Turns Packaged Messenger RNA Into A Linear Transcript." ScienceDaily. www.sciencedaily.com/releases/2009/02/090213113340.htm (accessed July 7, 2015).

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