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MBB342 > Polarised growth in yeast > Flashcards

Polarised growth in yeast Flashcards

1
Q

What is the difference between cell proliferation and cell growth?

A

Cell proliferations leads to an increase in the number of cells.
Cell growth is an increase in the size of an individual cell

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2
Q

How is yeast cell cycle and growth different to human cell cycle and growth?

A

In yeast the nucleus stays in tact until cytokinesis, whereas in MAN it breaks open

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3
Q

Define cell polarity

A

cell polarity means regions of the cell have distinct compositions and thereby have different capabilities and functions
(cell symmetry can be broken by organisation of proteins and lipids inside the cell and on the cell surface)

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4
Q

What are the four critical steps in polarisations leading to budding yeast?

A
  1. mark the site
  2. decoding the site
  3. establishing the site
  4. maintaining the site
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5
Q

What is the difference between axial and bipolar division?

A

Axial division occur in haploid cells, and the bud neck forms at the same pole as the birth scars
Bipolar division occurs at the opposite pole to the birth scar in the daughter cell and at either pole in the mother cell. (diploid cells)

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6
Q

What step is axial and bipolar division related to?

A

marking the site for bud development

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7
Q

What genes were identified to be important in axial division?

A

BUD10, BUD3 and BUD4

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8
Q

What genes were identified to be important in bipolar division?

A

BUD8, BUD9 and RAX2

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9
Q

How do these marking the site genes act in relation to eachother?

A

cannot function without all gene products present

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10
Q

What is the phenotype of bud10-, bud3- or bud4- mutants?

A

In haploid cells, axial budding is lost and it becomes bipolar.
In diploid cells there are no affects

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11
Q

What is the phenotype of bud8- mutants?

A

Mutants cannot bud at the distal pole - all buds form at the birth scar (ie axial)

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12
Q

What is the phenotype of bud9- mutants?

A

Cannot bud at proximal pole - all buds at distal pole.

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13
Q

What is the phenotype of bud8-/bud9- double mutant?

A

No pattern, random budding in diploid cells , and axial budding as haploid (WT)

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14
Q

What can the proteins discovered through studies of axial and bipolar budding be thought of as?

A

Landmark proteins

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15
Q

What set of genes interact with the landmark proteins?

A

BUD1, BUD2 and BUD5

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16
Q

How can you describe the signaling pathway that transmits the landmark signal?

A

Modular, requires every step (ie every gene product) in order to be functional

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17
Q

What type of product does BUD1 encode?

A

Ras related GTPase

18
Q

What type of product does BUD2 encode?

A

GAP

19
Q

What type of product does BUD5 encode?

A

GEF

20
Q

How does the landmark protein interact with the signaling module?

A

Landmark protein (eg BUD8) recruits BUD5 to convert BUD1-GDP to BUD1-GTP

21
Q

What family of proteins are prominent in polarity establishment leading to the set up of polarity axis in the budding/mother cell?

A

Rho-GTPases

22
Q

What is the most important Rho-GTPase in yeast?

A

CDC42

23
Q

What is the GEF to CDC42?

A

CDC24

24
Q

What is the phenotype of cdc42ts mutants at 37 degrees?

A

Isotropic growth and no axis of polarity established
Fail to bud and fail to polarise actin cytoskeleton. Only patches no actin cables.
Fail to form septin ring

25
Q

How does cdc24 interact with cdc42?

A

cdc24 binds to the active site of BUD1 and activates it allowing it to replace GDP with GTP

26
Q

How is cdc42 under temporal control by the cell cycle as well as spatial control from the landmark signaling cascade?

A

G1 cyclin CDK = cdc28.
Cdc28 activates CDC42 via many pathways.
FAR-1 sequesters cdc42 in the nucleus, and cdc28 phosphorylates FAR-1 allowing the release of cdc42 into the cytosol

27
Q

When does bud initiation occur in relation to the cell cycle?

A

Bud initiation takes place in late G1 phase, only happens once every cell cycle

28
Q

What is the GAP for cdc42?

A

BEM3

29
Q

What are some important effectors for polarised growth from activating cdc42?

A

Septins
Gic1/2
Formins, polarisome, actin cables
Sec3

30
Q

What is the polarisome?

A

A complex of proteins localised to the incipient (newly growing) bud site and tip of the newly growing bud

31
Q

What does the polarisome seem to be important for?

A

Seems to be important in linking cdc42 signaling to actin cable assembly, and for localising formin proteins Bni1 and Bnr1, important for driving actin assembly

32
Q

What is the function of actin cables in the actin cytoskeleton of yeast?

A

delivery of vesicles to the site of polarised growth

33
Q

What is the function of actin cortical patches in the actin cytoskeleton in yeast?

A

endocytosis

34
Q

What is the function of the contractile actomyosin ring in the actin cytoskeleton in yeast?

A

Septum formation

35
Q

What are septins?

A

Type of cytoskeletal element involved in cell polarity and cytokinesis - structurally related proteins containing a GTP binding domain

36
Q

In yeast, which septins associate in vivo to form a ring at the mother bud neck (and in vitro will associate to form filaments)?

A

cdc3, cdc10, cdc11 and cdc12

37
Q

What will the phenotype be of a protein mutant at the late stage polarity ‘maintaining the site’ be?

A

There will be formation of a bud, but all processes following the formation will be jeffed up

38
Q

What are the three most critical processes at the maintaining the site stage of bud polarity?

A
  • targeting vesicles to the actively growing site
  • polarised membrane growth
  • synthesis and directed deposition of new cell wall
39
Q

What is RHO1 essential for in maintaining the site of polarity?

A

Important for ensuring the cell wall machinery is at the site of bud growth

40
Q

What is the phenotype of rho1- mutant?

A

arrest cell cycle and lyse as small buds

MBB342 (3 decks)

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