Color-coded biosensor illuminates in real time how viruses attack hosts
Understanding how viruses invade host cell protein-making machinery

Date:
September 25, 2020
Source:
Colorado State University
Summary:
All viruses can only do damage by replicating inside the cells
of another organism, their host. Researchers have now shown
an important mechanism in this host-attacking process, at the
single-molecule level in living cells.



FULL STORY ========================================================================== Infectious viruses come in many shapes and sizes and use slightly
different attack mechanisms to make humans and animals sick. But all
viruses share something in common: They can only do damage by replicating inside the cells of another organism -- their host.


==========================================================================
This broad, fundamental process of how viruses trick host cells into
making copies of the virus has had a team of Colorado State University scientists captivated for several years. A collaboration between the labs
of Monfort Professor Tim Stasevich, in the Department of Biochemistry and Molecular Biology, and Associate Professor Brian Munsky, in the Department
of Chemical and Biological Engineering, is on a mission to understand,
in visual detail and with mathematical precision, all aspects of viral
attack strategies, including how viruses invade host cell protein-making machinery. Their work, supported by grants from the National Institute
of General Medicine and the W. M. Keck Foundation, could provide insight
into predicting and fighting back against all manner of viral diseases.

For the first time ever, the team has shown an important mechanism in this host-attacking process, at the single-molecule level in living cells,
and they have reproduced these behaviors in computational models. Their
new experiments and models, published in Nature Structural and Molecular Biology, reveal in unprecedented detail how viruses initiate translation
of genetic material into proteins.

Hijacking the host Since viruses do not encode their own replication
machinery, they hijack that of their host cells by stealing cellular
machines called ribosomes, which are essential for making proteins from
the genetic material found in RNA. Many viral genomes contain special RNA structures called Internal Ribosome Entry Sites, or IRES, that capture ribosomes from the host, forcing those ribosomes to make viral proteins.

Researchers know that when IRES-related RNA translation takes place,
the virus has succeeded in commandeering the host's ribosomes. The
CSU researchers invented a biosensor that lights up blue when viral
translation is happening, and green when normal host translation is
happening, in single living cells.

This design allows them to differentiate between normal host processes
and viral processes, in real time.



==========================================================================
The sensor combines the relevant bits of virus (not the whole virus) that interact with and steal host ribosomes, along with two distinct protein
tags that glow the moment RNA is translated. First author and graduate
student Amanda Koch spent more than a year developing the sensor, with
the goal of looking at host protein RNA translation, and virus-related
RNA translation, at the same time.

Luis Aguilera, a postdoctoral researcher in the Munsky group, built a
detailed computational model to reproduce Koch's fluorescence microscopy videos. By analyzing Koch's data through the lens of dozens of hypotheses
and millions of possible combinations, Aguilera discovered complex
biochemical mechanisms that the biochemists couldn't directly see. His
models showed that both healthy human RNA and viral RNA fluctuate between states that actively express proteins and those that are silent.

Cellular stress In addition to examining viral translation in normal
cells, Koch's biosensor allows the researchers to visualize the effects
of different types of stress that cells undergo when being attacked
by a virus, and how, where and when normal versus viral translation
increase or decrease. The integration of Koch's microscopy data and
Aguilera's computational models revealed that the relationship between
normal and IRES-mediated translation is largely one-sided -- in healthy
cells, normal translation dominates, but in cells under stress, IRES translation dominates.

The Stasevich and Munsky teams envision that the combination of their
unique biochemical sensors and detailed computational analyses will
provide powerful tools to understand, predict, and control how future
drugs might work to inhibit viral translation without affecting host translation.

Future COVID-19 applications As the researchers look ahead to the future,
they have their sights next set on COVID-19. Although SARS-CoV-2 does
not contain an IRES, according to Koch "our biosensor is modular and
can easily incorporate pieces of SARS-CoV-2 to explore how it uniquely
hijacks host replication machinery during infection." "We are proving,
more and more, that we can look at these nuanced dynamics of how viruses
are sneaking past their hosts to infect a lot of cells and make us sick,"
Koch said.


========================================================================== Story Source: Materials provided by Colorado_State_University. Original
written by Anne Manning. Note: Content may be edited for style and length.


========================================================================== Related Multimedia:
* Image_of_a_single_cell_that_shows_different_types_of_translation_in
different_colors,_using_a_color-coded_biosensor ========================================================================== Journal Reference:
1. Amanda Koch, Luis Aguilera, Tatsuya Morisaki, Brian Munsky,
Timothy J.

Stasevich. Quantifying the dynamics of IRES and cap translation
with single-molecule resolution in live cells. Nature Structural &
Molecular Biology, 2020; DOI: 10.1038/s41594-020-0504-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200925113636.htm

--- up 4 weeks, 4 days, 6 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)