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39 Cards in this Set
- Front
- Back
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Cell cycle checkpoints |
*arrest the cell cycle - if previous events have not been completed - if the environment is unfavorable |
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G1 checkpoint |
*cell cycle checkpoint (DNA damage checkpoint) - senses cell size - physiological state of cell - environmental conditions |
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G2 checkpoint |
*cell cycle checkpoint (DNA damage checkpoint) - ensures DNA is replaced completely/properly |
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Metaphase checkpoint |
*cell cycle checkpoint - ensures all chromosomes have attached to spindles |
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DNA damage checkpoint |
*cell cycle checkpoints - arrests cell cycle if DNA is damaged (ex: G1 checkpoint, G2 checkpoint) |
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G1 phase |
*cell cycle stage - making a decision whether or not to divide |
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S-phase |
*cell cycle stage - DNA replication |
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G2 phase |
*cell cycle stage - making preparations to divide |
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M-phase |
*cell cycle stage - mitosis and cytokinesis -- separates sister chromatids -- divides cell into two daughter cells |
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Regulations of G1-S phase transition |
1) Controlled by molecules (E2F/Rb) 2) Feedback loops |
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Molecules to control S-phase initiation |
*regulation of G1-S transition - E2F (transcriptional factor) - Retinoblastoma: Rb (regulatory proteins) |
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E2F |
*regulation of G1-S transition - Transcriptional factor - required for transcription of S-phase genes (G1/S cyclins, S-cyclins, DNA polymerase) - can transcribe itself - active when not bound to Rb |
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S-phase genes |
*regulation of G1-S transition - transcribed by active E2F to enter S-phase 1) G1/S cyclins 2) S-cyclins 3) DNA polymerase (makes S-cdk) |
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Retinoblastoma (Rb) |
*regulation of G1-S transition - Regulatory protein - binds and inhibits E2F (ex: presence of nitrogens) - inactive when phosphorylated by G1-Cdk accumulation |
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Feedback loops |
*regulation of G1-S transition - Sharpen G1/S transition - regulates itself - level of one substance influences levels of another in same system |
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Activation of Cdk/cyclin complex |
*regulation of G1-S transition *Feedback loops - binding of extracellular signal - phosphorylates Rb |
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Incomplete DNA replication |
*G2 checkpoint - blocks entry into mitosis - blocks cdc25= M-cdk inactive=no mitosis |
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G2 checkpoint |
*cell cycle checkpoint - ensures that initiation of mitosis cannot occur until DNA replication is complete |
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Cdc25 |
*regulates entry into mitosis - Activates M-cdk - Promotes entry into mitosis - Blocked by unreplicated DNA |
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Hydroxyurea |
*regulates entry into mitosis - inhibits DNA synthesis - cannot replicate DNA - cell arrested in S-phase by G2 checkpoint |
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Caffeine |
*regulates entry into mitosis - blocks G2 checkpoint mechanism - allows incomplete cells to undergo mitosis/replication |
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Unattached chromosomes to spindles |
*block sister chromatid separation (mitosis) - done by metaphase checkpoint |
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Metaphase checkpoint |
*cell cycle checkpoint - spindle assembly checkpoint - ensures sister-chromatid separation cannot occur until all chromosomes attached to spindle |
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Unreplicated kinetochore |
*regulates chromatid separation in mitosis - Blocks APC/Cdc20 interaction -- cannot separate sister chromatids (anaphase) -- cannot deactivate M-cdk (exit from mitosis) |
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APC |
*regulates chromatid separation in mitosis - attached to cdc20 (activation) - blocked by unreplicated kinetochore |
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Spindle assembly checkpoint mechanism |
*regulates sister chromatid separation in mitosis - activated by drugs - drugs destabilize MTs (ex: colchicine) |
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Colchicine |
*regulates sister chromatid separation in mitosis - drug activated by spindle assembly checkpoint (metaphase checkpoint) - destabilizes MTs |
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DNA damage |
- blocks cell cycle progression |
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DNA damage checkpoints |
*arrests the cell cycle until damage is repaired - two types of these in cells 1) G1 checkpoint 2) G2 checkpoint |
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G1 checkpoint |
*DNA damage checkpoint - prevents entry into S-phase if DNA damaged - controlled by p53 |
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p53 |
*controls G1 DNA damage checkpoint - low in normal cells - constantly degraded by ubiquitin/protosome - cannot be degraded when phosphorylated |
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Active p53 |
*G1 DNA damage checkpoint - when phosphorylated - cannot be degraded - Transcribes p21 gene -- blocks S-phase entry |
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P21 |
*G1 DNA damage checkpoint - Cdk inhibitor (CKI) - transcribed by active phosphorylated p53 - inactivated G1/S-Cdk and S-Cdk **Blocks entry into S-phase |
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G2 checkpoint |
*DNA damage checkpoint - prevents mitosis if DNA is damaged - blocks cdc25 with phosphorylation - blocks entry into mitosis |
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Blocks entry into mitosis |
*G2 DNA damage checkpoint - damaged DNA phosphorylates cdc25 |
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G1 phase |
*cell cycle phase - controlled by G1-cdk and G1/S-cdk |
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p53 |
*controls DNA damage *if DNA damaged... - blocks S-cdk - blocks G1/S-cdk |
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Cdc25 |
*related to M-cdk - blocked by unreplicated DNA - blocked by DNA damage |
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APC |
*part of metaphase-anaphase - blocked by unattached chromosome to spindle |
