Forum für Wissenschaft, Industrie und Wirtschaft

Hauptsponsoren:     3M 
Datenbankrecherche:

 

Scripps Research Institute scientists describe elusive replication machinery of flu viruses

23.11.2012
Scientists at The Scripps Research Institute (TSRI) have made a major advance in understanding how flu viruses replicate within infected cells.

The researchers used cutting-edge molecular biology and electron-microscopy techniques to "see" one of influenza's essential protein complexes in unprecedented detail. The images generated in the study show flu virus proteins in the act of self-replication, highlighting the virus's vulnerabilities that are sure to be of interest to drug developers.


The new Scripps Research Institute study shows flu virus proteins in the act of self-replication. Shown here is the influenza virus, which encapsidates its RNA genome (green) with a viral nucleoprotein (blue); the influenza virus polymerase (orange) reads and copies the RNA genome. In the background is an image of influenza virus ribonucleoprotein complexes observed using cryo-electron microscopy.

Credit: Image courtesy of the Wilson, Carragher and Potter labs.

The report, which appears online in Science Express on November 22, 2012, focuses on influenza's ribonucleoprotein (RNP). RNPs contain the virus's genetic material plus the special enzyme that the virus needs to make copies of itself.

"Structural studies in this area had stalled because of the technical obstacles involved, and so this is a welcome advance," said Ian A. Wilson, the Hansen Professor of Structural Biology at TSRI and senior author of the report with TSRI Professors of Cell Biology Bridget Carragher and Clint Potter. "The data from this study give us a much clearer picture of the flu virus replication machinery."

Unveiling the Mystery of RNPs

At the core of any influenza virus lie eight RNPs, tiny molecular machines that are vital to the virus's ability to survive and spread in its hosts. Each RNP contains a segment—usually a single protein-coding gene—of the RNA-based viral genome. This viral RNA segment is coated with protective viral nucleoproteins and has a structure that resembles a twisted loop of chain. The free ends of this twisted loop are held by a flu-virus polymerase enzyme, which handles the two central tasks of viral reproduction: making new viral genomic RNA, and making the RNA gene-transcripts that will become new viral proteins.

Aside from its importance in ordinary infections, the flu polymerase contains some of the key "species barriers" that keep, for example, avian flu viruses from infecting mammals. Mutations at key points on the enzyme have enabled the virus to infect new species in the past. Thus researchers are eager to know the precise details of how the flu polymerase and the rest of the RNP interact.

Getting those details has been a real challenge. One reason is that flu RNPs are complex assemblies that are hard to produce efficiently in the lab. Flu polymerase genes are particularly resistant to being expressed in test cells, and their protein products exist in three separate pieces, or subunits, that have to somehow self-assemble. Until now, the only flu RNPs that have been reproduced in the laboratory are shortened versions whose structures aren't quite the same as those of native flu RNPs. Researchers also are limited in how much virus they can use for such studies.

The team nevertheless managed to develop a test-cell expression system that produced all of the protein and RNA components needed to make full-length flu RNPs. "We were able to get the cells to assemble these components properly so that we had working, self-replicating RNPs," said Robert N. Kirchdoerfer, a first author of the study. Kirchdoerfer was a PhD candidate in the Wilson laboratory during the study, and is now a postdoctoral research associate in the laboratory of TSRI Professor Erica Ollmann Saphire.

Kirchdoerfer eventually purified enough of these flu RNPs for electron microscope analysis at TSRI's Automated Molecular Imaging Group, which is run jointly by Carragher and Potter.

Never Seen Before

The imaging group's innovations enable researchers to analyze molecular samples more easily, in less time, and often with less starting material. "We were able, for example, to automatically collect data for several days in a row, which is unusual in electron microscopy work," said Arne Moeller, a postdoctoral research associate at the imaging group who was the other first author of the study.

Electron microscopes make high-resolution images of their tiny targets by hitting them with electrons rather than photons of light. The images revealed numerous well-defined RNP complexes. To Moeller and his colleagues' surprise, many of these appeared to have new, partial RNPs growing out of them. "They were branching—this was very exciting," he said.

"Essentially these were snapshots of flu RNPs being replicated, which had never been seen before," said Kirchdoerfer. These and other data, built up from images of tens of thousands of individual RNPs, allowed the team to put together the most complete model yet for flu-RNP structure and functions. The model includes details of how the viral polymerase binds to its RNA, how it accomplishes the tricky task of viral gene transcription, and how a separate copy of the viral polymerase assists in carrying out RNP replication. "We're now able to take a lot of what we knew before about flu virus RNP and map it onto specific parts of the RNP structure," said Kirchdoerfer.

The new flu RNP model highlights some viral weak points. One is a shape-change that a polymerase subunit—which grabs viral RNA and feeds it to the polymerase's active site on a second subunit—has to undergo during viral gene transcription. Another is key interaction between the polymerase and viral nucleoproteins. Flu RNPs are long and flexible, curving and bending in electron microscope images; and thus the structural model remains only modestly fine-grained. "You wouldn't be able to design drugs based on this model alone," said Kirchdoerfer, "but we now have a much better idea of how flu RNPs work, and that does suggest some possibilities for better flu drugs."

The study, "Organization of the Influenza Virus Replication Machinery," was funded in part by grants from the National Institutes of Health (AI058113, GM095573) and the Joint Center for Innovation in Membrane Protein Production for Structure Determination (P50GM073197). TSRI's Automated Molecular Imaging Group includes the National Resource for Automated Molecular Microscopy, which is supported by the National Institutes of Health's National Center for Research Resources (2P41RR017573-11) and the National Institute of General Medical Sciences Biomedical Technology Resource Centers (9 P41 GM103310-11)

Jann Coury | EurekAlert!
Further information:
http://www.scripps.edu

More articles from Life Sciences:

nachricht More than just a mechanical barrier – epithelial cells actively combat the flu virus
04.05.2016 | Helmholtz-Zentrum für Infektionsforschung

nachricht Discovery of a fundamental limit to the evolution of the genetic code
03.05.2016 | Institute for Research in Biomedicine (IRB Barcelona)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Sei mit STARS4ALL dabei, wenn Merkur vor die Sonne wandert

2012 war es die Venus, in diesem Jahr ist der Planet Merkur dran, vor der Sonne zu passieren. Für fast acht Stunden werden wir am 9. Mai 2016 die Möglichkeit haben, den Planeten Merkur als kleinen schwarzen Punkt auf der Oberfläche der Sonne durchziehen zu sehen. Das EU-Projekt STARS4ALL, an dem auch das IGB beteiligt ist, wird in Zusammenarbeit mit www.sky-live.tv das Phänomen von Teneriffa und von Island aus live übertragen. STARS4ALL bietet dazu Bildungsmaterial für Schüler an.

Am 9. Mai 2016, um die Mittagszeit, wird der Planet Merkur anfangen, die Scheibe der Sonne zu kreuzen; eine Reise, welche über sieben Stunden dauern wird.

Im Focus: MICROSCOPE sendet

Am Montag, 2. Mai 2016, erreichte die Wissenschaftlerinnen und Wissenschaftler vom Zentrum für angewandte Raumfahrttechnologie und Mikrogravitation (ZARM) der Universität Bremen die erste Erfolgsmeldung von ihrem Forschungs-Satelliten. Per Videoübertragung waren sie zugeschaltet, als die französischen Kollegen das Experiment an Bord von MICROSCOPE (MICRO Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence) initialisierten und das Messinstrument die ersten Testdaten übermittelte. Damit ist der wichtigste Meilenstein der Testphase erreicht, bevor sich herausstellt, ob Einsteins Relativitätstheorie auch nach dieser Satellitenmission noch Bestand haben wird.

“#TSAGE @onera_fr is on. The test masses have been released and servo looped!!!! Great all green“ lautet die Twitter-Nachricht der französischen Partner, die...

Im Focus: Genauester Spiegel der Welt bei European XFEL in Hamburg eingetroffen

Der vermutlich präziseste Spiegel der Welt ist bei European XFEL in der Metropolregion Hamburg eingetroffen. Der 95 Zentimeter lange Spiegel ist ein wichtiges Bauteil des Röntgenlasers, der 2017 in Betrieb gehen soll. Auf den ersten Blick sieht er einem normalen Spiegel durchaus ähnlich, ist jedoch extrem flach und glatt. Die größten Unebenheiten auf seiner Oberfläche haben eine Dimension von gerade einmal einem Nanometer, einem milliardstel Meter. Diese Präzision entspräche einer 40 Kilometer langen Straße, deren maximale Unebenheit gerade einmal so groß ist wie der Durchmesser eines Haars.

Der Röntgenspiegel ist der erste von mehreren, die an unterschiedlichen Stellen der Anlage zum Spiegeln und Filtern des Röntgenlaserstrahls eingebaut werden....

Im Focus: Erste Filmaufnahmen von Kernporen

Mithilfe eines extrem schnellen und präzisen Rasterkraftmikroskops haben Forscher der Universität Basel erstmals «lebendige» Kernporenkomplexe bei der Arbeit gefilmt. Kernporen sind molekulare Maschinen, die den Verkehr in und aus dem Zellkern kontrollieren. In ihrem kürzlich in «Nature Nanotechnology» publizierten Artikel erklären die Forscher, wie bewegliche «Tentakeln» in der Pore die Passage von unerwünschten Molekülen verhindern.

Das Rasterkraftmikroskop (AFM) ist kein Mikroskop zum Durchschauen. Es tastet wie ein Blinder mit seinen Fingern die Oberflächen mit einer extrem feinen Spitze...

Im Focus: Nuclear Pores Captured on Film

Using an ultra fast-scanning atomic force microscope, a team of researchers from the University of Basel has filmed “living” nuclear pore complexes at work for the first time. Nuclear pores are molecular machines that control the traffic entering or exiting the cell nucleus. In their article published in Nature Nanotechnology, the researchers explain how the passage of unwanted molecules is prevented by rapidly moving molecular “tentacles” inside the pore.

Using high-speed AFM, Roderick Lim, Argovia Professor at the Biozentrum and the Swiss Nanoscience Institute of the University of Basel, has not only directly...

Alle Focus-News des Innovations-reports >>>

Anzeige

Anzeige

IHR
JOB & KARRIERE
SERVICE
im innovations-report
in Kooperation mit academics
Veranstaltungen

Diabetes Kongress in Berlin beginnt heute

04.05.2016 | Veranstaltungen

UFW-Fachtagung im Vorzeichen von Big Data und Industrie 4.0

03.05.2016 | Veranstaltungen

analytica conference 2016 in München - Foodomics, mehr als nur ein Modebegriff?

03.05.2016 | Veranstaltungen

 
B2B-VideoLinks
Weitere VideoLinks >>>
Aktuelle Beiträge

Beim Laden von Lithium-Luft-Akkus entsteht hochreaktiver Singulett-Sauerstoff

04.05.2016 | Energie und Elektrotechnik

Sei mit STARS4ALL dabei, wenn Merkur vor die Sonne wandert

04.05.2016 | Physik Astronomie

Mehr als eine mechanische Barriere - Epithelzellen kämpfen aktiv gegen das Grippevirus

04.05.2016 | Biowissenschaften Chemie