41 BIOS Biology Core I: Cellular and Molecular Spring 2008
Lecture 25, March 26 Cell-Cycle Control (Chapter 18, pages 611-625)
Overview of the Cell Cycle
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The Eucaryotic Cell Cycle is Divided into Four Phases.
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Feedback from the intracellular events of the cell cycle, as well as signals from the cell's environment, determine whether the control system will pass through certain checkpoints.
Progression through the cell cycle depends on cyclin-dependent protein kinases (Cdks)
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Cdk active only when cyclin is bound.
"Cyclical changes in cyclin concentrations help drive the cyclic assembly and activation of the cyclin-Cdk complexes; activation of these complexes in turn triggers various cellcycle events, such as entry into S phase M or phase." page 616.
The rise and fall of M-Cdk activity during the cell cycle.
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"The sudden fall in M-cyclin concentration toward the end of mitosis is the result of its rapid destruction by the ubiquitin-dependent proteolytic system." page 617.
The activity of Cdks is regulated by cyclin degradation.
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Different cyclin-Cdk complexes trigger different stages in the cell cycle.
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DNA damage arrests the cell cycle in G1.
"One of the best understood checkpoint mechanisms halts the cell cycle in G1 if DNA is damaged, helping to ensure that a cell does not replicate damaged DNA." page 623.
The cell-cycle control system can arrest the cycle at various checkpoints.
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