Cancer cells proliferate uncontrolled, so regulation of the entry into the cell division cycle by external hormonal and stress stimuli is a central theme of cancer research. In contrast to animals, plants appear to have strong preventive mechanisms to avoid this kind of uncontrolled cell division. On the other hand, and unlike animal cells, plant cells that fulfill specific functions and are therefore differentiated are able to reactivate cell division. This is the reason why it is possible to regenerate new plants from individual cells in tissue culture. However, because of the differences between plants and animals, the identification of functions regulating the plant cell cycle may provide an important lesson about how evolutionary changes have led to less rigorous control of cell proliferation in mammals.
In all eukaryotes, the cell cycle is regulated by enzymes called cyclin-dependent protein kinases
(CDKs). Plants harbour several different CDKs that are all related to their yeast and animal
counterpart. Activation of the cell cycle at various control points requires the phosphorylation
of CDKs by CDK-activating kinases (CAKs) that represent important targets within cellular
signaling pathways. Two major types of CAKs have so far been identified. One type establishes
contact with the machinery necessary to provide the template (messenger RNA) to produce
proteins within a cell according to the DNA blueprint. This machinery is called the
transcriptional apparatus and contains an enzyme called RNA polymerase II complex, which is
necessary to produce the messenger RNA. These CAKs, known from animals and fission
yeasts, make contact to a particular part of a subunit of the RNA polymerase II complex. The
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Contact: Csaba Koncz
koncz@mpiz-koeln.mpg.de
+49-221-5062-230
Max-Planck-Gesellschaft
8-May-1998