This is a presentation by Philip Kaldis
from the Institute of Molecular and
Cell Biology, IMCB from Singapore.
I will tell you about our
investigations into the regulation of
the cell cycle in vivo,
using mouse model systems.
The cell cycle is divided in four
different phases 'S' phase where DNA is
replicated and the 'M' phase or
mitosis where the cells physically divide.
And in between we have the so
called gap phases G1 and G2.
These gap phases are actually very
important in preparing the events in 'S'
phase in mitosis and also to monitor
the completion of these events.
So they contain the so
called check points.
The transitions between one cell cycle
phase to the next one is promoted by
cyclin-dependent kinases and on the slide,
I've indicated some of these kinases.
Cyclin-dependent kinase belong to
a superfamily of protein kinases,
consisting of 20 members in mammals and
generally Cdks are small molecules
of about 30 to 40 KiloDalton.
They consist of a better rich N-terminus,
and a helix C-terminus and
in between, you can see the ATP
binding sites in here as well as
the so-called T-loop or
activation segment in red or in yellow.
Now, on the right side, in purple,
you see a fragment of cyclin A.
Cyclin molecules are highly unstable
proteins that are synthesized and
degraded throughout the cell cycle.
So, for example, cyclin E is synthesized
in G1 and degraded in S phase.
Cyclin A is synthesized in S phase and
degraded in the middle of mitosis and
cyclin B is synthesized at the end of S
phase and has to be degraded at the end
of mitosis in order for the cells
to be able to exit the cell cycle.