cell polarity in yeast

Question 1

what are the 4 stages in generating cell polarity?

Answer 1

• marking the site
• decoding the site
• establishing the site
• maintaining the site

Question 2

what stain is used to follow budding events?

Answer 2

calcofluor- binds chitin

Question 3

what do cells with axial gene mutants show in haploid cells?

Answer 3

bipolar budding

Question 4

how were genes involved in bud site selection identified?

Answer 4

identified the genes that allowed recovery of cells with random budding pattern to be recovered to normal phenotype

Question 5

genes for axial budding

Answer 5

BUD 10,3,4 and septins

Question 6

what do these axial budding proteins do

Answer 6

mark the mother bud neck during one cycle as the site for budding of the next cycle

Question 7

bipolar budding genes

Answer 7

BUD8,9 AND RAX2 and actin cytoskeleton

Question 8

where does bud8 mark?

Answer 8

distal end of cell

Question 9

where does bud9 mark?

Answer 9

proximal end of cell- adjacent to bud scar

Question 10

what do double bud8bud9 cells do in diploids?

Answer 10

bud randomly

Question 11

what is the role of rax2p?

Answer 11

is present at both poles and maintains bipolar budding over multiple generations

Question 12

what genes are required for both patterns?

Answer 12

bud1, 2 and 5

Question 13

what is the role of these genes required for both patterns?

Answer 13

decode the axial/bipolar marks and signal to machinery involved in generating the polarity axis

Question 14

what do mutations in bud 1,2,5 cause?

Answer 14

random budding

Question 15

bud 1 is a GTPase and is activated by what?

Answer 15

bud5

Question 16

bud1 GAP is what?

Answer 16

bud2

Question 17

how did they identify polarity establishment genes?

Answer 17

found that many mutants blocked in signalling and could not advance cell cycle. cdc42,24,43 mutants could not direct their growth to form a new bud

Question 18

at restrictive temp what can ts cdc42 mutants not do?

Answer 18

establish polairty

Question 19

bud1 recruits what protein?

Answer 19

cdc24- the GEF for cdc42. so cdc42 activated and polarity established

Question 20

where is cdc42 lolcalised in G1 and S and G2

Answer 20

bud tip

Question 21

where is cdc42 localised in G2/M?

Answer 21

around whole bud

Question 22

where is cdc42 localised in late anaphase/telophase

Answer 22

bud neck

Question 23

what regulates spatial and temporal control of the cell cycle?

Answer 23

cdc28 (G1 cyclin-GDK)

Question 24

how does cdc28 regulate availability of cdc42s GEF?

Answer 24

cdc28 phosphorylates Far1 so it is broken down. cdc24 can then be released from nucleus to cytosol and is recruited by bud1 so it can activate cdc42

Question 25

how does cdc28 regulate cdc42s GAP?

Answer 25

inhibits the Rga2/Bem3/Bem2 complex- the GAP

Question 26

cdc28 promotes accumulation of what complex?

Answer 26

Boi1/Boi2/Bem1/ced24 complex- GEF. the cdc42 can recruit its own GEFto amplify signal. allows budding even without landmark proteins- but random

Question 27

cdc42 effectors

Answer 27

Ste20, septins, gic1/2, sec3, polarisome/formins/actin cables

Question 28

why is the polarisome important?

Answer 28

links Rho-GTPase signalling to actin filament assembly and localisation of formin proteins Bni1 and Bnr1 whcih drive actin cable assembly

Question 29

what are septins

Answer 29

landmark proteins with Gtp binding domain and coiled coil region

Question 30

what septins form a ring at the mother neck in vivo

Answer 30

cdc3,10,11,12

Question 31

what is the purpose of the septin ring in cytokinesis?

Answer 31

forms a boundary between mother and bud to limit material exchange

Question 32

why is rho1 important?

Answer 32

ensures that cell wall machinery is active at sites of growth

Question 33

how is endocytosis involved in maintaining the site?

Answer 33

membrane proteins are removed by endocytosis and recycled or degraded. proteins dissociate from membrane and relocalise through secretory vesicle association