Flashcards in 29_Cell Cycle II Deck (15)
Where does Wee-1 phosphorylate cdc2 at?
What protein phosphorylates cdc2 at Thr-161?
CAK (cyclin activating kinase)
What enzyme dephosphorylates cdc2 at Tyr-15? What is the result of this?
Result: activation of the MPF and entry into mitosis
Wee 1 is a (+/-) regulator and cdc25 is a (+/-) regulator of mitotic entry.
Wee 1: -
What do wee 1 mutants look like? Why?
They are small (wee). Since these cells cannot keep cdc2 in an inactive state, they divide prematurely (G2 is too short).
Why can't cdc25 mutants enter mitosis?
They cannot remove inhibitory phosphate from Tyr-15.
How does proteolysis regulate CDK activity?
proteolysis of cyclins can be both an accelerator and brake
How does subcellular localization of cyclins regulate CDKs?
accelerates (e.g. translocate to nucleus, and become 'trapped' there)
Which cyclin's levels oscillate the least?
What does pRB do in its activated state?
represses genes required for S phase
During G1, what is E2F bound to?
pRB (and the gene promoter)
What effect does CDK activation have on pRB?
pRB is phosphorylated => becomes inactive
E2F is released, and transcription is activated
What class of proteins inhibit cyclin/CDK activity in early G1?
CDIs (cyclin-dependent kinase inhibitors)
Which CDI family are binary inhibitors? Ternary?