1. Cell Cycle Regulation1 Cell-cycle Control & Death Chapter 18 You will not be responsible for: details of S-CdK function mechanisms of spindle assembly and anaphase specific details of the caspase cascade & bcl-2 family topics on extracellular signals (pp 636- 640) not covered in class Review mitosis on your own  Panel 18-1, etc Read on your own about cytokinesis in plant and animal cells pp 630 - 633 Questions in this chapter you should be able to answer: Chapter 18: 1 - 5, 10, 12, 13, 14, 16, 17, 20, 25, 26 all but C, 28, 30

2. Cell Cycle Regulation2 How is cell division and growth regulated? Growth factors -- stimulate cell growth Mitogens -- trigger cell division -- e.g., EGF, phytoestrogens Survival signals -- disable apoptotic mechanisms

3. Cell Cycle Regulation3 What are the stages of the cell-cycle? -- a review G 1 S G 2 M G 0 Table 18–1 Some Eucaryotic Cell-Cycle Times Cell type Cell cycle time Early frog embryo cells ~30 minutes Yeast cells 1.5–3 hours Intestinal epithelial cells ~12 hours cultured fibroblasts ~20 hours Human liver cells ~1 year

4. Cell Cycle Regulation4 How is progress through cell cycle regulated? “Cell-cycle control system” The ‘Checkpoint’ model -- not a ‘domino’ process How are they controlled? -- intracellular and extracellular signals What are the effectors -- lots of kinases & phosphatases

5. Cell Cycle Regulation5 How is cell cycle progress studied? Different systems -- yeast: cell cycle mutations -- frog: big dividing embryos -- sea urchin & clam: many embryos Asynchronously dividing cells DNA/nucleus staining Flow cytometry Synchronously dividing cells Ques 18-2 Where are G 1,S,G 2, & M stage cells? DAPI stained cells

6. Cell Cycle Regulation6 What did study of frog embryos reveal about the control system? Be sure to read How we know Frog egg cytoplasmic transfer experiments Something in the cytosol triggers mitosis -- called MPF Activity of MPF oscillates during the cell cycle What is MPF?

7. Cell Cycle Regulation7 What did sea urchin & clam embryos reveal? Population of synchronously dividing embryos S 35 labeling, SDS-PAGE, autoradiography Revealed cyclic synthesis & breakdown of certain proteins Called cyclin

8. Cell Cycle Regulation8 What do we know about MPF & cyclin? MPF is a cyclin bound to a Cdk ‘cyclin-dependent protein kinase’ = M-Cdk Several Cyclins and Cdks -- regulate different cell cycle events Table 18–2 The Major Cyclins and Cdks of Vertebrates Cyclin–Cdk Complex Cyclin Cdk partner G 1 -Cdk cyclin D Cdk4, Cdk6 G 1 /S-Cdk cyclin E Cdk2 S-Cdk cyclin A Cdk2 M-Cdkcyclin B Cdk1

9. Cell Cycle Regulation9 How is cyclin-CDK activity regulated? Two processes 1. Synthesis & destruction of cyclin -- ubiquination -- proteasomes 2. Inactivation & activation -- Activating/inhibitory Kinases/phosphatase -- Pos feedback  rapid activation

10. Cell Cycle Regulation10 How do cyclin-cdk’s trigger cellular events? S-Cdk triggers DNA replication -- activates replication origins -- blocks reactivation What does activated M-CDK do? 1)Phosphorylates H1 histone (triggering C’some condensation) 2)Disassembly of nuclear lamina 3)Changes behavior of microtubules -- phosphorylates MAPs 4)etc…??

11. Cell Cycle Regulation11 How does activated S-Cdk trigger DNA replication? Origin of Replication Complex (ORC) CDC-6 rises during G1 -- helps build replication fork complex -- helicase, polymerase, etc S-CDK activates replication complex -- inhibits ORC

12. Cell Cycle Regulation12 How is cyclin-Cdk coupled to checkpoint control? Tumor suppressor genes -- inactivation can dispose cell toward tumor formation -- P53, P21 and Rb are all TSGs -- loss of both alleles necessary Why? P53 can also trigger apoptosis Figures 18-14 + 18-15

13. Cell Cycle Regulation13 What is Apoptosis? -- “programmed cell death” Apoptosis vs necrosis When does apoptosis occur? Normal organism / cell develop damaged/ infected/ cancerous cells Sculpting of mouse paw Question 18-10, p 635 Why apoptosis rather than necrosis? Apoptosis

14. Cell Cycle Regulation14 What are the mechanism of apoptosis activation and cellular destruction? Intrinsic vs extrinsic activation Caspase family of proteases -- activation ‘cascade’ Intrinsic activation signals -- cell injury, P53 activation, etc -- lack of survival signal Extrinsic activation signals -- cell-surface receptors (Fas/FasL) -- cellular toxins (Granzymes) Caspase cascade Intrinsic pathway