Cyclins

it is important, that the cyclins are changed during the cycle, that is, for each phase, you need another cyclin. If it wasn't degraded, the cell would be arrested.

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aptitude: I think cyclins activate CDK, AKA cyclin dependent kinase

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Cyclins A, D, E, G2/M, and B.

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... kinases (CDKs). These enzymes (in budding yeast there is actually only one, propably also in the fission yeast S.pombe) are regulated by cyclins (http://en.wikipedia.org/wiki/Cyclin). Different cyclin variants are only expressed during different cell cycle phases to enable the activation ...

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... phase cyclin/CDK, then it is marked for UbQ by SCF. With APC/C, a protein called Cdh1 is attached to the ACTIVE APC/C that ubiquinates mitotic cyclins. When G1 cylin-CDKs are expressed then Cdh1 becomes phosphorylated by them and the Cdh1 then releases the APC/C, making it inactivated. As far ...

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