10-24: Cell control/division II Flashcards
What are the steps of the cell cycle and checkpoints?
1) Enter cell cycle and proceed to S phase
2) G2/M checkpoint: enter MITOSIS
3) Metaphase-to anaphase: Enter ANAPHASE and proceed to cytokinesis
Start checkpoint in late G1
starts DNA replication and S phase of cell cycle
Orgins of replication
Specific sites where DNA replication occurs
Prereplication complex
Late mitosis-early G1
- assembles at the orgins of rep
- DNA replication origin licensing
Preinitiation complex
Nucleated at the onset of S phase
ORC
Pre-replication protein
- loads other initiation proteins Cdc6 and Cdt1
Mcm
Helicase
- loads to ORC, Cdc6, Cdt1 to form the pre-replication protein
Licensing control prevents ________
re-replication
What does the preinitiation complex do to pre-RC complex?
- Cdc6 degradation and Cdt1 inhibition
- Phosphorylation of ORC (can’t recruit)
S-cdk
pre-initiation complex
What increases at G2/M checkpoint that drives entry to mitosis?
M-Cdk
What does M-cdk induce?
-mitotic spindle
-chrom condensation
-nuc envelope breakdown
-chrom alignment
-anaphase entry
Prophase
-chrom condense
-centrosomes move to opposite sides of cell
-nucleoli disappear
Prometaphase
-MT attatch to kinetochores
-metaphase plate
Anaphase
-sister chromatids pulled apart
-chromatids are moved towards opposite poles by shortening of the spindle MTs
Telophase
chromosomes decondensed
spindle apparatus disassembles (nucloili reapear)
Cdc25 phosphatase
removes the inhibitory phosphates from M-cdk = activation
Active m-cdk
- Promotes Cdc25 activity
- Inhibits Wee1
What is securin’s role in Metaphase to anaphase transition?
- securin bound to separase
- cdc20 binds to the active APC/C
- active apc/c degrades securin
- separase cleaves cohesion
- sister chromatids separated
Mitogen
Stim G1/S-cdk
Growth factors
stim protein syth and inhibit protein degration
Survival factors
suppress apoptosis
GTPase Ras
- activated by mitogen
- signaling protein that activates MAP kinase and causes gene expression
Ras/MAPK
Gives a signal from the extracellular environment to the nucleus for the cell to grow, divide, or differentiate
Myc
- early gene expression (ras/mapk) causes activation
G1-Cdk
Activates E2F, which regulates DNA synthesis
Activation of E2F
Mitogen induced cell cycle entry and S phase initiation
Growth factors
affect concentrations of cyclins and CDKs
Rapamycin (TOR)
nutrient-sensing signaling network that controls cell growth
