Chapter 18 & 19 lecture

Chapter 18 & 19 lecture - Combined: Chapter 18: Cell Cycle...

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1 Combined: Chapter 18: Cell Cycle and Apoptosis & Chapter 19 Cell Division These chapters will NOT be on Exam 3 BUT they will be on Final Exam Cell cycle control & cell death G o
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2 Control system G 2 check point Q. is DNA intact & replicated? Can we proceed? G 1 check point Q. is DNA intact? Is environment favorable? Can we proceed? Four phase of a cell cycle: 1. M-phase 2. G1 - Gap 1 3. S-phase - DNA replication 4. G2 - Gap2 Cell Cycle Control: Basic principle - Cdk-cyclin dimer cyclic activation and deactivation of key protein (complexes) that regulate initiation of DNA synthesis and M-phase regulation by cell cycle kinases = cyclin dependent protein kinases = Cdks involved in key phosphorylation & dephosphorylation events kinases always present in cell so ACTIVITY is regulated by cyclins Cdk protein level constant, but activity levels cycle cyclins - level of protein fluctuates with period of cycle controlled by rate of synthesis and massive degradation at key spot in cell cycle What part of the graph shows “massive” degradation? e.g. M-cyclin regulates onset of M-phase
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3 Cyclin degradation • e.g. M-cyclin - regulates onset of M-phase (red curve) • at M/G1 boundary - no M-cyclin present • concentration slowly builds back up such that gradual accumulation helps time onset of mitosis • activates M-Cdk to initiate M-phase • near end of mitosis M-cyclin is rapidly and completely degraded • use a ubiquitination pathway- how? • APC - anaphase promoting complex adds ubiquitin to M-cyclin and targets it from degradation A self-regulatory or auto-regulatory loop: increase M-Cdk activity stimulated by increased amounts M-cyclin M-Cdk activity phosphorylates APC complex to initiate ubiquitination of M-cyclin [& segregation chromosomes] M-cyclin targeted for degradation which inhibits M-Cdk activity ? M_Cdk_active.jpg and yet one (two) more levels of control …. •M-cyclin levels steadily increase BUT M-Cdk activity is even more restricted • M-Cdk is NOT activated by M-cyclin unless it is first phosphorylated by another kinase AND dephosphorylated by a phosphatase
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This note was uploaded on 04/02/2008 for the course BIO 2600 taught by Professor Vanburkem during the Winter '08 term at Wayne State University.

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Chapter 18 & 19 lecture - Combined: Chapter 18: Cell Cycle...

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