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stem cells aging and cancer > cell cycle > Flashcards

cell cycle Flashcards

1
Q

DEFINE: cell cycle clock

A

network of interacting proteins in the nucleus that receives signals from outside and inside the cell, integrates them and decides the cell’s fate

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2
Q

how does excessive proliferation occur?

A
  • produce growth factors by themselves —-> autocrine stimulation of cell proliferation
  • stimulate normal cells to produce growth factors
  • deregulate downstream signalling of growth factor
    > overexpress GF receptors
    > ligand independent firing
  • inhibit negative feedback mechanisms that control proliferative signalling
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3
Q

how long does G1 last?

A

8-10 hours

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4
Q

how long does S phase last?

A

6-8 hours

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5
Q

what are some methods used to study the cell cycle?

A
  • flow cytometry

- immunofluorescence and epifluorescence microscopy

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6
Q

describe how flow cytometry is used to study the cell cycle

A
  1. treat cells with fluorescent dye
  2. more fluorescence = more DNA present
    - DNA content doubles during S phase so intensity of fluorescence also doubles
    - cells in G0 or G1 have half the fluorescent signal as cells in G2 or M phase
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7
Q

describe how immunofluorescence

is used to study the cell cycle

A
  1. label microtubules using primary and secondary antibodies conjugated to a fluorophore
  2. observe changes in organisation of microtubules during the different phases of mitosis
    - cells during different phases of mitosis will have different morphology
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8
Q

describe how epifluorescence is used to study the cell cycle

A
  1. stain cells with nuclear staining = epifluorescence
  2. observe changes in organisation of DNA during the different phases of mitosis
    - cells during different phases of mitosis will have different morphology
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9
Q

there is a window of time for the cell to consult the extracellular environment on a decision to proceed with cell division or not. what is it?

A

start of g1 to 1-2 hours before g1-to-s phase transition

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10
Q

what are the targets of CDK?

A
  • centrosome associated proteins promoting centrosome duplication
  • proteins controlling dna replication that are activated by phosphorylation
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11
Q

what do cyclins do?

A

associate with cdk and increase the catalytic activity of cdk
helps with substrate recognition –> cdk phosphorylates correct target

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12
Q

what does MPF do?

A

induces cell entry into m phase
binds cyclin B to cdc2
phosphorylates cdc2
linked to protein kinase activity which oscillates throughout the cell cycle

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13
Q

which cdks form a complex with cyclin d?

A

cdk4/6

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14
Q

which cdk forms a complex with cyclin e?

A

cdk2

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15
Q

which cdk forms a complex with cyclin a

A

cdk2

then cdk1/cdc2

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16
Q

which cdk forms a complex with cyclin b?

A

cdc2/cdk1

17
Q

which cdk forms a complex with cyclin c?

A

cdk3

18
Q

what is the decrease in cyclin levels throughout the cell cycle mediated by?

A

ubiquitination-dependent degradation

19
Q

which cyclin/cdk complexes can INK4 CKIs inhibit?

A

cyclin d + cdk4/6 only

20
Q

what are the INK4 proteins?

A

p16INK4A
p15INK4B
p18INK4C
P19INK4D

21
Q

which cyclin/cdk complexes can kip CKIs inhibit?

A

all other cyclin/cdk complexes aside from cyclin d/cdk4.6

22
Q

what are the kip proteins?

A

p57Kip2
p27Kip1
p21cip1

23
Q

what is the role of TGFβ signalling during the EARLY stages of tumourigenesis?

A

arrests growth of a variety of cell types

24
Q

what is the role of TGFβ signalling during the LATER stages of tumourigenesis?

A

promotes tumour invasiveness and formation of metastases

25
Q

how does TGFβ control the cell cycle?

A
  • strongly increases expression of p15INK4B -> cells do not reach R point –> blocks proliferation
  • weakly induces p21Cip1 upon dna damage –> cell cycle halted until genome is repaired
  • inhibits myc expression + prevents myc from binding cki promoters
26
Q

how do growth factors control cell cycle progression?

A
  1. growth factor binds to receptor
  2. PI3K pathway activated
  3. Akt/PKB activated
  4. Akt phosphorylates p21Cip1
  5. phosphorylated p21Cip1 translocates to cytoplasm so cannot inhibit cyclin/cdk complexes
27
Q

what is the kaplan meir survival curve?

A

non-parametric statistical method used to estimate survival function

stem cells aging and cancer (10 decks)

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