Cell Cycle 6 Flashcards
What is the site of phosphorylation required to activate all cdks?
Threonine ~160 in the t loop
What is the affect of cyclin binding cdk on t loop?
Causes T loop to undergo conformational change, which is then phosphorylated by CAK (cyclinH/cdk7)
What phosphorylates cdk t loop?
cdk7/cyclin H (CAK)
this further opens the binding site
Other than opening the binding site, what does the ~160Y phosphorylation?
The negative charge is important in aligning the consensus sequence - (S/T)Px(R/K) -, which has a positive residue, in the binding site
What is the consensus sequence for cdks?
(S/T)Px(R/K)
What else does CAK (cyclin H/cdk7) target?
RNA polymerase
What is the function of Wee1?
Inhibits cdk2 by phosphorylation. This prevents early division.
What are the human equivalents of wee1?
Myt1, Mik1
What type of kinase is Wee1?
tyrosine/theorine
What is the consensus sequence of wee1?
GxGxxG - the ceiling of the ATP binding site. Phosphorylation blocks access to ATP
on cdks t14/15
Name an agonist of Wee1?
cdc25
What activates Wee1?
DNA damage - as a result cyclinD/cdk4 gets phosphorylated so Rb can’t be phohsphorylated
Is wee1 a tumour supressor?
yes
What is cdc25?
A phosphatase which reactivates cdks after inhibitory phosphorylation - target T/Y
What 3 pieces of evidence is there that Cyclin-E/cdk2 phosphorylation results in release of E2F?
1) antibody initiation results in cells accumulating in G1
2) Inhibition with Roscovitine (ATP analgoue) causes G1 arrest
3) Expression of dominant negative cdk2 (145D –> N) which can not longer coordinate Mg2+ ion causes G1 arrest
What happens when a KO mouse for cyclin E1/2 is created?
Mostly normal development - slightly slower division
Why do cyclin E1/2 KO mice have mostly normal development?
Other cyclins take there place. Only cyclin required in cyclin is cyclin A and cdk1
What is the affect os roscovitine in Rb null cells?
No affect because no downstream pathway
What is roscovitine?
cdk2 inhibitor (ATP analogue) - hence can inhibit other cdks (also can inhibit pyridoxal kinase also inhibited)
What is bortezomib?
Proteasome inhibitor (inhibits chymotrypsin part of proteosome which is involved in p27) - not specific to p27
What 4 molecules can stabilise p27?
C1, C2, C16, C20
How do C1, C2, C16, C20 stabilise p27?
Interrupts p27 interaction with skp2
