F lec 17

Question 1

the separation of the mitotic cell into 2 daughter cells - cell membrane pinches and completely separates into 2 new daughter cells

Answer 1

cytokinesis

Question 2

cytokinesis occurs at the _____________ of where mitosis occurred and this ensures that sister chromatids on either pole of the spindle are effectively separated from eachother

Answer 2

midzone

Question 3

the thin bridge that connects the 2 daughter cells before they completely split - contains remnants of the central spindle, actin/myosin, and matrix material

Answer 3

midbody

Question 4

the midbody that forms in cytokinesis consists of _______________ __________________ which are the last pieces of the 2 new daughter cells to break apart - interact until everything has moved over

Answer 4

interpolar microtubules

Question 5

the interpolar microtubules that make up the midbody form the signal that instructs cytokinesis to occur at this site, localizing actin and myosin to the midbody, forming the _______________ _____________

Answer 5

contractile ring (referred to by swan as a “purse string”)

Question 6

2 main proteins that localize at the midbody and interact to form the contractile ring:

Answer 6

actin, myosin

Question 7

in cytokinesis, _____________ is the protein associated with the cell membrane involved in the pulling motion that creates the cleavage furrow (slide 6)

Answer 7

actin

Question 8

the protein __________ is essential for the assembly of the actin/ myosin contractile ring

Answer 8

RhoA

Question 9

RhoA is only active when bound to _________

Answer 9

GTP

Question 10

the _______ for RhoA activates it

Answer 10

GEF

Question 11

the _______ for RhoA deactivates it

Answer 11

GAP

Question 12

RhoA is activated near the ____________ _____________

Answer 12

central spindle (interpolar microtubules)

Question 13

Experiment to see whether RhoA was necessary for contractile ring formation and cytokinesis:

Answer 13

JUST READ IT

Question 14

in the experiment to determine the importance of RhoA, what technique did we use prior to immunostaining to create the differentially expressed cell lines?

Answer 14

RNAi (RNA interference)

Question 15

_____________________ is a drug that depolymerizes actin, and when added actin is no longer detected in the cell, there is no pinching of the cell membrane, there is no localization of the myosin heavy chain, and cytokinesis does not occur BUT RHOA STILL LOCALIZES PROPERLY

Answer 15

latrunculin A

Question 16

when latrunculin A is added, which protein still localizes properly ?

Answer 16

RhoA (therefore RhoA independent of actin and therefore comes first in the pathway)

Question 17

when we RNAi for ______________ ____________ ____________, no cytokinesis occurs, the myosin heavy chain is absent, RhoA is still present, and actin accumulation is still present

Answer 17

myosin heavy chain

Question 18

pathway for cytokinesis initiation:

Answer 18

RhoA —> Actin —> Myosin

Question 19

the GEF for RhoA, whose activity allows RhoA to localize at the central spindle in the first place

Answer 19

ECT2

Question 20

ECT2 _______________ RhoA

Answer 20

activates

Question 21

ECT2 does not localize at the midbody on the cell membrane, but rather it localizes on the ________________ _________________ within the cell - so presumably the ECT2 GEF is able to activate the RhoA located on the cell membrane at the midbody

Answer 21

interpolar microtubules

Question 22

ECT2 is necessary for _______________ ___________ formation

Answer 22

contractile ring (actin and myosin accumulation at the midbody)

Question 23

a known microtubule binding protein that associated with the mitotic spindle specifically at interpolar microtubules throughout mitosis

Answer 23

CYK4

Question 24

__________ still localized to the interpolar microtubules even in the ECT2 knockdown cells

Answer 24

CYK4 (therefore CYK4 is upstream of ECT2 and RhoA in the pathway)

Question 25

___________ is necessary for cytokinesis, the localization of actin and myosin, as well as the localization of ECT2 and RhoA

Answer 25

CYK4

Question 26

protein pathway that is required for contractile ring formation: (5 proteins)

Answer 26

CYK4 ---> ECT2 ---> RhoA ---> Actin ---> Myosin

Question 27

experiment to determine how RhoA activation is controlled such that it is only active after mitosis:

Answer 27

JUST READ IT

Question 28

in ______________ it was found that ECT2 and CYK4 cannot bind

Answer 28

metaphase

Question 29

in _______________ it was found that ECT2 and CYK4 could bind

Answer 29

anaphase

Question 30

ECT2 is gradually _________________ throughout the cell cycle

Answer 30

dephosphorylated

Question 31

phosphorylation of ECT2 ________________ correlates to its inability to bind to CYK4

Answer 31

directly (as phosphorylation increases, inability to bind increases (gets worse and worse binding))

Question 32

drug that inhibits CDK1 activity that was used to experiment whether CDK1 phosphorylates ECT2

Answer 32

Roscovitine

Question 33

experiment to determine CDK1 role in phosphorylating ECT2:

Answer 33

Roscovitine

Question 34

experiment to determine CDK1 role in phosphorylating ECT2:

Answer 34

metaphase

Question 35

experiment to determine CDK1 role in phosphorylating ECT2:

Answer 35

cyclin B

Question 36

experiment to determine CDK1 role in phosphorylating ECT2:

Answer 36

JUST READ IT

Question 37

cyclin destruction in ________________ permits ECT2 recruitment to the spindle midzone because then it is no longer being phosphorylated by CDK1

Answer 37

anaphase

Question 38

model for RhoA activation at the contractile ring:

Answer 38

CYK4

Question 39

model for RhoA activation at the contractile ring:

Answer 39

CDK1 phosphorylation

Question 40

model for RhoA activation at the contractile ring:

Answer 40

APC

Question 41

model for RhoA activation at the contractile ring:

Answer 41

dephosphorylation

Question 42

model for RhoA activation at the contractile ring:

Answer 42

RhoGEF

Question 43

model for RhoA activation at the contractile ring:

Answer 43

RhoA