Cell Cycle 2 Flashcards

1
Q

how is the metaphase-anaphase tansition triggered

A

by regulated proteolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are S-CDK and M-CDK complexes regulatroy targets of

A

the anaphase promoting complex or cyclosome (APC/C)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how does APC/C trigger cells to go through mitosis

A

anaphase promoting complex act by ubiquitin groups covelantly to cyclins- this is then degraded by proteosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is APC/C and why does it target proteins

A

ubiquitin ligase and targets for degredation by proteosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

describe 3 features of APC/C

A

small
covalently attached
ubiquitin covalently attched to lysin side chain on target protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

how are polyubiquitin chains formed

A

by linking additional ubiquitin chains by Lys48

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how is degradation by proteosomes triggered

A

by adding more ubiquitin to create long chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the 3 different domains of ubiquitin

A

unfoldase ring
central cyclinder-protease
cap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how is APC/C activated

A

Cdc20 activates in mid-mitosis

Cdh1 activates from late mitosis to G1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what happens when s and m-cdk activity is abolished

A

proteins previously phosphorylated in s phase to early mitosis need to be dephosphorylated before mitosis and cytokinesis can be completed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how do you get out of mitosos

A

must remove phophates essentially reversing effect of protein kinases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is securin

A

the second major target of APC/C in mitosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what does securin do

A

acts by inhibiting activity of protease called seperase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what happens when securin is degraded

A

at the end of metaphase by APC/C this frees seperase to cleave one of the subunits of a protein complex called cohesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what happens when there is a loss of cohesion

A

result in sister chromatid seperation in anaphase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how does separase break cohesion complex

A

breaks ring keeping chromatids together

17
Q

describe the contrasting roles of cyclin cdk and apc/c

A

cyclin-cdk activity drives cell cycle progression

apc/c action triggers chromosome segregation

18
Q

what is SCF

A

another ubiquitin ligase but one that functions in s phase

19
Q

what does SCF do

A

targets various CKIs for destruction in late G1 and is responsible for G1/S cyclin destruction in early S phase

20
Q

compare APC/C and SPF

A

functions mid mitosis to G1
15 subunits
requires actiavtion by Cdc20 and Cdh1

functions in G1-S transition
5 subunits
always present by requires substaret to be phosphorylates

21
Q

why is S-CDK activity required

A

for initiation of chromosome replication

22
Q

how is replication initiation triggered

A

by increase in s-cdk activity

23
Q

what is activated at each stage of cycle

A

s pahse= scdk
mphase= mcdk
g1= apc/c and cdk inactivation

24
Q

what do s-cdk phosphorylate

A

two proteins Sld2 and Sld3 and this facilitates assembly of CMG complex

25
what drives entry into mitosis
psotive feedback loop causes sharp increase in M-CDK activity
26
what triggers cytokinesis events
APC/C destruction of securin and cyc;ins
27
how is APC/C sister chromatin seperaration achievde
by securin degradation resulting in activation of seperase which cleaves cohesion to open cohesion ring
28
what happens if one chromosome fails to align on spindle
unattached chromsome kinetichore binds to Mad2 protien which undergoes conformational change to inhibit cdc20-APC/C