Feedback Control Between Sphase and Mitosis Feedback control
Feedback Control Between S-phase and Mitosis Feedback control ensures dependency of cell cycle events
DNA Damage Checkpoints Sensors: (i. e. Rad 9) Transducers: Targets: From Susan Forsburg, Salk Institute : Targets http: //pingu. salk. edu/~forsburg/cclecture. html
Chromosome Movements During Mitosis From Rieder and Salmon (1998) Trends Cell Biol. 8: 310
What if There Were No Checkpoint? Lodish et al. Figure 13 -33
The Mitotic Spindle Assembly Checkpoint Ensures the Order of Mitotic Events What has to Happen for Proper Chromosome Segregation? - Sister Chromatid Cohesion established in S-phase - Chromosome condensation in G 2 - Mitotic Spindle Assembly in Mitosis - Chromosome alignment in Mitosis - Metaphase/Anaphase transition (M/A) -securin degradation leads to cohesion destruction Mitotic checkpoint has to be upstream of M/A - Once you start destroying cohesion there’s no going back
The Mitotic Spindle Assembly Checkpoint aka Kinetochore Checkpoint Mitotic Checkpoint Metaphase Checkpoint Spindle Checkpoint… Mitotic Checkpoint Inhibits Cohesion Destruction -via inhibition of APCCdc 20 Mitotic Checkpoint Also Inhibits Mitotic Exit -via inhibition of APCCdh 1
The Metaphase to Anaphase (M/A) Transition From Zhou et al. (2002) J. Cell Sci. 115: 3547
How do We Know There’s a Checkpoint? Prometaphase Metaphase Adapted From Shimoda and Solomon (2002) Cell 109: 9
How do We Know There’s a Checkpoint? Variable Prometaphase 20 min. Metaphase Regardless of the length of Prometaphase, Metaphse lasts 20 minutes… Adapted From Shimoda and Solomon (2002) Cell 109: 9
Cohesion is Established in S-phase Cdc 6 ORC MCM Proteins ORC pre. RC Origin Assembly / Activation Actvie Cohesin Replication Factors Cdc 28 ORC ORC Cdc 7 Elongating Repl. Fork Origin Firing From Susan Forsburg, Salk Institute Origin Inactivation http: //pingu. salk. edu/~forsburg/cclecture. html
Cohesion is Established in S-phase Pds 5 Scc 3 Scc 1 Smc 1 Condensin From Uhlman (2001) Cur. Op. Cell Biol. 13: 754 Smc 3 Cohesin
Cohesion is Established in S-phase Condensin Chromosome Compaction Cohesin Chromosome Cohesion Scissile Subunit (Scc 1) Cleaved at M/A From Uhlman (2001) Cur. Op. Cell Biol. 13: 754
Condensin is Required for Chromosome Compaction Cohesin is Required for Chromosome Compaction
Condensin is Required for Chromosome Compaction Cohesin links Condensin from adjacent sister chromatids
From Susan Forsburg, Salk Institute http: //pingu. salk. edu/~forsburg/cclecture. html
The Metaphase to Anaphase (M/A) Transition From Zhou et al. (2002) J. Cell Sci. 115: 3547
Evidence for the Existence of a Checkpoint Needle 20 min. Micromanipulation of Chromosomes in Grasshopper Spermatocytes Adapted From Nicklas (1997) Science 275: 632
Micromanipulation of Chromosomes in Grasshopper Spermatocytes From Nicklas (1997) Science 275: 632
Kinetochores Generate the Checkpoint Signal Variable Adapted From Shimoda and Solomon (2002) Cell 109: 9 20 min.
Kinetochores Generate the Checkpoint Signal Variable 20 min Laser Ablate Kinetochore from last Mono-oriented Chromosome Adapted From Shimoda and Solomon (2002) Cell 109: 9
From Rieder et al. (1995) J. Cell Biol. 130: 941
Laser Anaphase From Rieder et al. (1995) J. Cell Biol. 130: 941
Unattached Kinetochores Cause a Checkpoint Delay From Musacchio and Hardwick (2002) Nature Reviews 2: 731
Both Attachment and Tension are Monitored 3 F 3 Epitope Phosphorylation of unknown proteins -dims upon attachment -disappears upon tension From Rieder and Salmon (1998) Trends Cell Biol. 8: 310
Both Attachment and Tension are Monitored Mono-oriented Grasshopper Spermatocyte Chromosomes Tension Relaxed Applied 3 F 3 Epitope Present in the absence of tension Adapted From Nicklas (1997) Science 275: 632 3 F 3 Epitope Disappears when tension applied
One More Yeast Screen: MADs and BUBs Search for Genes Responsible for Feedback Control of Mitosis Hoyt: Budding Uninhibited by Benomyl Bub 1, Bub 2, Bub 3 Li: Mitotic Arrest Deficient Mad 1, Mad 2, Mad 3
Spindle Assembly Checkpoint Components Gene Molecular Function Checkpoint Function Bub 1 Protein Kinase Transduction Bub 2 Tem 1 GAP (Mitotic Exit) Bub 3 Kinetochore Scaffold Mad 1 Generates Mad 2/Cdc 20 Complex Mad 2 Inhibits Cdc 20 Mad 3/Bub. R 1 (vert) Protein Kinase Generates Mad 2/Cdc 20 Complex Mps 1 Protein Kinase Transduction Ipl 1 Protein Kinase Corrects Mono-orientation CENP-E Molecular Motor Trasduction, Congression Dynein Molecular Motor Congression, Checkpoint Off
APC is the Target of the Mitotic Checkpoint The Metaphase to Anaphase (M/A) Transition From Zhou et al. (2002) J. Cell Sci. 115: 3547
Potential Checkpoint Targets:
APC is the Target of the Mitotic Checkpoint From Zhou et al. (2002) J. Cell Sci. 115: 3547
APC is the Target of the Mitotic Checkpoint Cdc 2/Cyclin B Mad 2 Mad 3/Bub. R 1 Cdc 2/Cyclin B Adapted from Peters (2002) Mol. Cell 9: 931 Bub 2
Spindle Assembly Checkpoint Pathways Securin Separase Adapted From Susan Forsburg, Salk Institute http: //pingu. salk. edu/~forsburg/cclecture. html
Mitotic Exit is a Spindle Checkpoint Target Bub 2 active: NO Cdc 14 Release Mitotic Exit Network (MEN) Bub 2 inactive: Cdc 14 Released From Susan Forsburg, Salk Institute http: //pingu. salk. edu/~forsburg/cclecture. html
Bub 2 Prevents Cdc 14 Release/Cdh 1 Activation Bub 2 Cdc 2/Cyclin B Bub 2 Cdc 14 Sequestered in Nucleolus Cdc 14 Released Cdc 14
APC is the Target of the Mitotic Checkpoint Cdc 2/Cyclin B Mad 2 Mad 3/Bub. R 1 Cdc 2/Cyclin B Adapted from Peters (2002) Mol. Cell 9: 931 Bub 2
Spindle Assembly Checkpoint Pathways Securin Separase From Susan Forsburg, Salk Institute http: //pingu. salk. edu/~forsburg/cclecture. html
Checkpoint is Mediated by Rearrangement of Mad 2 Complexes From Millband et al. (2002) Trends Cell Biol. 12: 205 Mad 2 Inhibits APCCdc 20
Mad 2 Cycles Through Kinetochore and Inhibits Cdc 20 Shah and Cleveland (2000) Cell 103: 997
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