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| Heidelberg, 27 September 2006 |
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| How nature tinkers with the cellular clock
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![Three organisms use the same molecular machines [represented as grey boxes], but regulate different parts [highlighted in green, yellow and red in human, budding yeast and fission yeast].](press27sept06s.jpg) |
Three organisms use the same molecular machines [represented as grey
boxes], but regulate different parts [highlighted in green, yellow and red in
human, budding yeast and fission yeast]. |
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Many solutions have evolved to control the timing of the same biological
process
Press
Release 27 September 2006 [PDF]
The life of a cell is all about
growing and dividing at the right time. That is why the cell cycle
is one of the most tightly regulated cellular processes. A control
system with several layers adjusts when key components of the
cell cycle machinery are produced, activated and degraded to
make sure that the schedule is kept. These layers of control work
differently and are usually studied separately, but researchers at
the European Molecular Biology Laboratory [EMBL] and the
Technical University of Denmark [DTU] have now discovered
that they change in a highly coordinated fashion during evolution.
The study, which will be published in this week's online
issue of Nature, also reveals that although most components of
the cell cycle have been conserved over one billion years, the temporal
regulation of this process has evolved remarkably fast.
The cell cycle is so fundamental for a cell that its machinery has
been almost entirely conserved through evolution. Crucial components
are made only at specific times to ensure that each
machine is active only during the right phase of the cycle.
Comparing cell cycle genes that are conserved between humans,
yeasts and thale cress, Peer Bork and colleagues at EMBL and
DTU found that while many genes in each organism are
expressed only at specific times of the cell cycle, it is not the same
genes that are temporally regulated in each species.
"Regulating processes by controlling the time at which genes are
expressed is a strategy that is conserved," says Peer Bork, joint
coordinator of EMBL's Structural and Computational Biology
Unit, "but details of which genes are regulated in this way and the
exact timing of their expression have changed a lot throughout
evolution. What is really surprising is the speed at which these
regulatory systems evolve. We are talking about roughly 100 million
years for a big change. On the timescale of evolution this is
incredibly fast for such a central process."
To have a safety net when temporal control at the gene level fails,
cells also regulate the activity of cell cycle proteins directly,
switching them on and off and modifying them at particular sites.
A closer look at these proteins revealed that changes in the control
of gene expression often go together with changes in the regulation
of the corresponding protein.
"To our surprise, we found that these two different mechanisms
of temporal control evolve together in a coordinated fashion,"
says Søren Brunak, Professor at DTU. "This double layer of control
seems so important that evolution has conserved it despite
dramatic changes in the regulation of each mechanism."
The new insights gained have broad implications. The principles
discovered might govern also the control of other temporally regulated
systems like embryonic development. The fast evolution of
temporal regulation also raises the question in how far general
conclusions about regulatory systems can be drawn from studying
simple model organisms like yeast or fruit flies.
Source Article
L.J. Jensen, T.S. Jensen, U. de Lichtenberg, S. Brunak & P. Bork. Co-evolution of transcriptional and posttranslational cell cycle
regulation. Nature online, 27 September 2006
Press Contact
Anna-Lynn Wegener
Press Officer
EMBL Heidelberg
Tel: +49 +6221 387-8452
Email: wegener@embl.de |
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