Feedback Control Between S-phase and Mitosis ck control ensures dependency of cell cycle
Mar 27, 2015
Feedback Control Between S-phase and Mitosis
Feedback control ensures dependency of cell cycle events
Sensors:(i.e. Rad9)
Transducers:
Targets:
DNA Damage Checkpoints
http://pingu.salk.edu/~forsburg/cclecture.htmlFrom Susan Forsburg, Salk Institute
:Targets
From Rieder and Salmon (1998) Trends Cell Biol. 8:310
Chromosome Movements During Mitosis
Lodish et al. Figure 13-33
What if There Were No Checkpoint?
What has to Happen for Proper Chromosome Segregation?- Sister Chromatid Cohesion established in S-phase- Chromosome condensation in G2- 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 Ensures the Order of Mitotic Events
Mitotic Checkpoint Inhibits Cohesion Destruction-via inhibition of APCCdc20
The Mitotic Spindle Assembly Checkpoint
Mitotic Checkpoint Also Inhibits Mitotic Exit-via inhibition of APCCdh1
aka Kinetochore CheckpointMitotic CheckpointMetaphase CheckpointSpindle Checkpoint…
From Zhou et al. (2002) J. Cell Sci. 115:3547
The Metaphase to Anaphase (M/A) Transition
Adapted From Shimoda and Solomon (2002) Cell 109:9
How do We Know There’s a Checkpoint?
Prometaphase Metaphase
Adapted From Shimoda and Solomon (2002) Cell 109:9
20 min.Variable
How do We Know There’s a Checkpoint?
Regardless of the length of Prometaphase,Metaphse lasts 20 minutes…
Prometaphase Metaphase
Cohesion is Established in S-phase
Cdc6
ORC ORC ORC
ORC
ORC
ORC
MCM Proteins
Cdc28
Cdc7
Cdc28
Replication Factors
Origin Assembly / Activation
preRC
Origin Firing Origin Inactivation
Elongating Repl. Fork
ActvieCohesin
http://pingu.salk.edu/~forsburg/cclecture.htmlFrom Susan Forsburg, Salk Institute
Cohesion is Established in S-phase
CondensinCohesin
From Uhlman (2001) Cur. Op. Cell Biol. 13:754
Scc1
Scc3Pds5
Smc1 Smc3
Cohesion is Established in S-phase
CondensinCohesin
ChromosomeCompaction
ChromosomeCohesion
Scissile Subunit (Scc1)Cleaved at M/A
From Uhlman (2001) Cur. Op. Cell Biol. 13:754
Condensin is Required forChromosome Compaction
Cohesin is Required forChromosome Compaction
Condensin is Required forChromosome Compaction
Cohesin is Required forChromosome Compaction
Cohesin links Condensinfrom adjacent sister chromatids
http://pingu.salk.edu/~forsburg/cclecture.htmlFrom Susan Forsburg, Salk Institute
QuickTime™ and aVideo decompressorare needed to see this picture.
From Zhou et al. (2002) J. Cell Sci. 115:3547
The Metaphase to Anaphase (M/A) Transition
20 min.
Evidence for the Existence of a Checkpoint
Needle
Micromanipulation of Chromosomes inGrasshopper Spermatocytes
Adapted From Nicklas (1997) Science 275:632
Micromanipulation of Chromosomes inGrasshopper Spermatocytes
From Nicklas (1997) Science 275:632
Adapted From Shimoda and Solomon (2002) Cell 109:9
20 min.Variable
Kinetochores Generate the Checkpoint Signal
20 min.Variable
Laser Ablate Kinetochorefrom last
Mono-oriented Chromosome
20 min
Kinetochores Generate the Checkpoint Signal
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
From Musacchio and Hardwick (2002) Nature Reviews 2:731
Unattached Kinetochores Cause a Checkpoint Delay
From Rieder and Salmon (1998) Trends Cell Biol. 8:310
Both Attachment and Tension are Monitored
3F3 EpitopePhosphorylation of unknown proteins -dims upon attachment -disappears upon tension
Both Attachment and Tension are Monitored
3F3 EpitopePresent in the
absence of tension
Mono-oriented Grasshopper Spermatocyte Chromosomes
Relaxed TensionApplied
3F3 EpitopeDisappears when
tension applied
Adapted From Nicklas (1997) Science 275:632
One More Yeast Screen: MADs and BUBs
Hoyt: Budding Uninhibited by Benomyl Bub1, Bub2, Bub3
Li: Mitotic Arrest Deficient Mad1, Mad2, Mad3
Search for Genes Responsible for Feedback Control of Mitosis
Spindle Assembly Checkpoint Components
Gene Molecular Function Checkpoint FunctionBub1 Protein Kinase Transduction
Bub2 Tem1 GAP (Mitotic Exit)
Bub3 Kinetochore Scaffold
Mad1 Generates Mad2/Cdc20 Complex
Mad2 Inhibits Cdc20
Mad3/BubR1 BubR1 (vert) Protein Kinase Generates Mad2/Cdc20 Complex
Mps1 Protein Kinase Transduction
Ipl1 Protein Kinase Corrects Mono-orientation
CENP-E Molecular Motor Trasduction, Congression
Dynein Molecular Motor Congression, Checkpoint Off
From Zhou et al. (2002) J. Cell Sci. 115:3547
APC is the Target of the Mitotic Checkpoint
The Metaphase to Anaphase (M/A) Transition
Potential Checkpoint Targets:
From Zhou et al. (2002) J. Cell Sci. 115:3547
APC is the Target of the Mitotic Checkpoint
APC is the Target of the Mitotic Checkpoint
Cdc2/Cyclin B
Cdc2/Cyclin B
Adapted from Peters (2002) Mol. Cell 9:931
Mad2Mad3/BubR1
Bub2
http://pingu.salk.edu/~forsburg/cclecture.htmlAdapted From Susan Forsburg, Salk Institute
Spindle Assembly Checkpoint Pathways
Securin
Separase
http://pingu.salk.edu/~forsburg/cclecture.htmlFrom Susan Forsburg, Salk Institute
Bub2 active:NO Cdc14 Release
Bub2 inactive:Cdc14 Released
Mitotic Exit is a Spindle Checkpoint Target
MitoticExit
Network(MEN)
Cdc14 Sequesteredin Nucleolus
Cdc14 Released
Cdc2/Cyclin B Cdc2/Cyclin B Cdc14
Bub2
Bub2 Prevents Cdc14 Release/Cdh1 Activation
Bub2
Cdc2/Cyclin B
Cdc2/Cyclin B
Adapted from Peters (2002) Mol. Cell 9:931
Mad2Mad3/BubR1
Bub2
APC is the Target of the Mitotic Checkpoint
http://pingu.salk.edu/~forsburg/cclecture.htmlFrom Susan Forsburg, Salk Institute
Spindle Assembly Checkpoint Pathways
Securin
Separase
Checkpoint is Mediated by Rearrangement of Mad2 Complexes
From Millband et al. (2002) Trends Cell Biol. 12:205
Mad2 InhibitsAPCCdc20
Shah and Cleveland (2000) Cell 103:997
Mad2 Cycles Through Kinetochore and Inhibits Cdc20