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M-Foundations of Medicine > 7W: The Cell Cycle > Flashcards

7W: The Cell Cycle Flashcards

1
Q

Cell Cycle Overview

A

Cell is quiescent but then gets a signal
G1: Gap Phase 1. Cell growth. longest phase of cell cycle
S: Synthesis of DNA
G2: Growth
M: Mitosis and Daughter cell division

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2
Q

Mitogen

A
  • control cell cycle by acting on G1 of the cell cycle
  • binds to receptor which trigger signaling pathways
  • this can induce transcription/translation of proteins involved in gene expression
    Ex. Myc
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3
Q

G1 Phase

A
  • Gap phase 1
  • cell energy level is high
  • increase protein synthesis
  • increased ribosome production
  • some organelle duplication
  • increase in cell size
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4
Q

mTOR complex

A
  • mammalian target of rapamycin
  • protein complex (kinase) that controls the cells desire to get bigger
  • has the ability to sense nutrients
    NOT AN ONCOGENE, but often regulated differently in cancers
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5
Q

Tuberous Sclerosis

A
  • disease that occurs when mTOR is on all the time
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6
Q

S Phase

A
  • phase where DNA is duplicated

- many origins of replication

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7
Q

licensing factors

A
  • Cdc6 and Cdt1
  • Rises in late G1/early S
  • Degraded during S phase
  • Geminin inhibits Cdt1. highest in S and G2
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8
Q

Cohesins

A
  • a 4 subunit complex that keeps the dublicated chromosomes from S phase tightly bound as sister chromatids
  • holds it all together. like a cage
  • breakdown of cohesins occurs late in mitosis
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9
Q

G2 Phase

A
  • cell checks for size, if the DNA is duplicated, and if the DNA was duplicated correctly
  • if everything is good, it moves to M phase
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10
Q

M Phase (1 hour)

A

Prophase:
a. early prophase - chromosomes condense
b. late prophase - centrosomes move apart
c. prometaphase - breakdown of nuclear envelope
Metaphase:
Chromosomes align along equator
Anaphase:
a. early anaphase - sister chromatids separate and daughter chromosomes move toward poles
b. late anaphase - spindle poles move farther apart
Telophase:
daughter nuclei have formed

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11
Q

What turns on the cell cycle?

A
  • cyclins
  • cyclin dependent protein kinases (CDKs)
  • Protein Degradation
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12
Q

What turns off the cell cycle?

A
  • transcriptional repressors
  • cyclin dependent kinase inhibitors
  • check points
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13
Q

Cyclins and CDKs of the cell cycle

A

Cyclin D - CDK4 and CDK6 - promotes passage through G1
Cyclin E - CDK2 - Allows cell to pass from G1 to S
Cyclin A - CDK2 - promotes passage through S phase
Cyclin B - CDK1 - Allows cell to pass from G2 to M

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14
Q

ways of CDK1 inhibition

A
  1. inhibitory phosphorylation
    - CDK1 can be activated and inhibited by phosphorylations
  2. Make no cyclin
  3. Cyclin degradation
    - CDK1 is active when bound to cyclinB
  4. Inhibitory protein
    - binds to the fully functional CDK1 molecule and inactivates it
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15
Q

How does CDK1 initiate M phase?

A
  • assembly of mitotic spindle
  • chromosome condensation
  • nuclear envelope breakdown
  • actin cytoskeleton rearrangement
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16
Q

ways of CDK1 activation

A
  1. Removal on Inhibitory phosphate
    - CDK1 dephosphorylation of the inhibitory phosphate is done by Cdc25
  2. Stimulation of CDK1 production
    - Active CDK1 is in a positive feedback loop of itself
  3. Activating phosphorylation
    - CDK1 can be activated and inhibited by phosphorylations
  4. Stimulation of cyclin production
17
Q

Role of Ubiquitin Ligase during cell cycle

A
  • we have to destroy cyclins to move through to the next phase of the cell cycle
    Ex. If CDK1 is always on, you’re always stuck in prophase
18
Q

2 main ubiquitin ligase complexes in cell cycle

A

SCF complex: Degrades things at G1/S

APC/C complex: Degrades things at M phase

19
Q

Retinoblastoma (Rb) Protein

A
  • regulation of the G1/S checkpoint
  • binds and inhibits DNA transcription
  • is increasingly phosphorylated through G1 and into S phase
  • as more phosphorylation occurs, Rb begins to release E2F (a TF) and once the cells makes it to S phase, Rb is completely unbound to E2F and it can bind to increase transcription
20
Q

HPV and Cervical Carcinomas

A
  • HPV virus makes a protein called E7
  • E7 binds to Rb and leads to it’s degradation
  • This loses our G1/S checkpoint
  • Gardasil is a vaccine that guards against the HPV viruses that make this E7 protein

M-Foundations of Medicine (23 decks)

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