Cell growth + division lecture 5

Question 1

Cortical stiffness in anaphase

Answer 1

• Sea urchin eggs, how much suction needed

- Stiffness ↑ immediately after cell is cleaved

Question 2

Microtubules needed for cell cleavage

Answer 2

• Colchine inhibits M + cell cleavage if applied b4 A

- MT involved in deciding when cell cleaved

Question 3

Actin filaments needed for cell contraction

Answer 3

• Actin = disorganised in cells w/ cytochalasin
• Needed for cell division
• Acts w/ myosin

Question 4

Anaphase spindle formation

Answer 4

• Forms as cell exits Mit
• In metaphase, spindles capture chromosome
• In A, this ↑ in no. as ends are captured by PRC1 + MKLP1
• PCL1 = dimer, opposite orientation
• Assoc/ w/ KIF4A which transports PRC1 to + end of microtubule

Question 5

Control of anaphase spindle elongation

Answer 5

• PRC1 restricted to ‘tags’ at + end by KIF4A

- Narrow band of overlapping microtubule

Question 6

Aurora B localises to anaphase spindle

Answer 6

• Transported from chromatin to central spindle by kinesin motor MKPL2
• Phosph KIF4A + promotes PRC1 transport

Question 7

PLK1

Answer 7

• Localises to centrosome + anaphase spindle
• PRC1 = binding partner
• In A, PRC1 binds microtubules, becomes phosph by PLK (binds through PBD), PLK promotes cell cleavage
• Phosphatase removes CDK phosphorylation

Question 8

Protein phosphatases

Answer 8

• PP2A vs PP1
• PP2A = trimeric E
• B56 + B56 are inhibited in M by CDK

Question 9

MASTL

Answer 9

• Greatwall kinase in flies
• CDK1-cyclin B activates
• If deplete = delayed entry into M
• Greatwall is activated by CDK + in turn inhibits PP2A by phosph ENSA
• Cyclin B is destroyed → great wall inactivate → ENSA slowly dephosph → PP2A active → PRC1 dephosph

Question 10

PLK1 recruitment of ECT2 RhoGEF

Answer 10

• Centraspindlin = MLKP1 + CYK4
• Phosph by PLK1 + docks Rho GEF ECT2
• CDK phosph Ect2, centraspindlin + PCR1 is inactive

Question 11

How cells shape change controlled

Answer 11

• Rho regulate actin cytoskeleton
• Active RhoA recruit formin + RHOK → triggers actin polymerisation → RHOK targets mysoin
• Myosin generates force

Question 12

Mibody formation

Answer 12

• Formed during telophase
• Physical barrier
• Abscision = ESCRT-III
• CEP55 interacts w/ ESCRT III
• MLKP1 compressed to form nobody