Goldilocks had to try all three bowls of porridge to find
the one that was just the right temperature. Likewise,
nasty bacteria lurking in the warm mush would need to
test the temperature inside Goldilocks' belly before deciding
whether to unleash their fury. A new study shows that
one bacterium does this by using its RNA as a sensor.
 |
Lighting the way. Listeria RNA
changes shape at body temperature and allows fluorescent
proteins to glow
CREDIT: STÉPHANIE
SEVEAU |
The bacterium Listeria monocytogenes is no
fairy tale. It causes flulike symptoms and occasionally
severe neurological effects in people with weakened
immune systems and pregnant women. Although the bug
can grow at temperatures ranging from 5¡ã to 45¡ãC, it
only causes disease within a few degrees of normal body
temperature (37¡ãC). But until now, how Listeria
senses temperature has been a mystery.
Listeria turns out to have a very clever trick,
explains Jörgen Johansson, a microbiologist at
the Pasteur Institute in Paris. His team has found that
part of Listeria's messenger RNA (the template
for protein synthesis) folds into a bobby-pin-like structure.
This unusual shape prevents ribosomes--the button-shaped
organelle that zips along the messenger RNA and strings
together amino acids into proteins--from binding to
the appropriate piece of RNA. At body temperature, this
RNA obstacle changes shape, allowing protein synthesis
to proceed.
Johansson and his colleagues discovered that by mutating
the structure of the bobby-pin-like RNA, they could
cause the virulent protein to be expressed at low temperatures.
The RNA structure also functions as a temperature sensor
when introduced into bacteria other than Listeria,
making it useful as a tool to manipulate gene products,
they report in the 6 September issue of Cell.
Such a temperature gauge could be a useful way to control
genes that are not normally thermally regulated, says
Jon Goguen, a microbiologist at the University of Massachusetts
Medical School in Worcester. "I think it's fair to call
it a major advance in the field." Johansson's group
thinks so too; they've already submitted a patent for
Listeria's RNA thermometer.
--ERICA GOLDMAN
Related sites
Pasteur Institute
General information
about Listeria
