BSI Lecture 21-22 Cell Cycle Control Flashcards
T or F? MAPK activates G1-CDK and G1/S-CDK by phosphorylating them.
False
T or F? G1-CDK and G1/S CDK activate S-CDK by phosphorylating it.
They phosphorylate Rb
P21 inhibits?
G1/S-CDK and S-CDK
CdKs must be bound to _______ to be active.
cyclin
What are CdKs?
Cyclin dependent kinases
Cyclin bound to a CdK forms a _________ ______.
Cyclin-CDK complex
How are cyclin degraded?
By the ubiquitan-proteasome system
There are a variety of cyclin-CdK complexes, what are they?
G1-CDK, G1/S-CDK, S-CDK, and M-CDK
Aside from cyclin binding, CdKs can also be regulated by _____ ___ and ______ ________ proteins (e.g p21, p27)
Phosphorylation status; CDK inhibiting proteins
T or F? Cyclin-Cdks are active in early G1.
False, not active
In mammals, what external cellular signal is required to initiate the cell cycle?
Mitogen
Epidermal GF, fibroblast GF, vascular endothelial GF, platelet derived GF, neurotrophic GF, insulin-like GF, hepatic GF, are examples of __________ ________ / ________
Growth factors/mitogen
Mitogen stimulates activity of _____ and ____ which leads to activation of S-CdK and transition into S-phase.
G1-CDK and G1/S-CDK
_____ activity is responsible for transition through the M-phase.
M-CDK
T or F? At the end of M-phase/beginning of Gl phase, all active CdKs are inactivated
True
G1-CDK and G1/S-CDK phosphorylates _______.
Rb
Phosphorylation of Rb leads to the release of _____.
E2F
______ is a transcription factor that regulates the transcription of genes necessary for S-phase
E2F
DNA polymerase and S-CDK Cyclin are regulated by ______
E2F
Mitogen binding leads to stimulation of the ____/_____ pathway
Ras/MAPK
MAPK activates a gene regulatory protein (transcription factor) , what is the example Dr Naylor gave in class?
ELK2
The ELK2, a transcription factor, increases the transcription of ____
Myc
_____ is a transcription factor which then regulates the transcription of several more genes, including cyclin D, SCF subunit, and E2F
Myc
Cyclin D expression leads to the activation of _______
G1-CDK
SCF subunit expression leads to the degradation of p27, which leads to activation of G1/S-CDK: SCF is what kind of protein?
Ubiquitan-ligase
T or F? Increased E2F expression and increased release of E2F from Rb leads to enhanced expression of genes required for S-phase.
True
DNA damage leads to activation of either ____ or _____ kinsase which then phosphorylates p53.
ATM or ATR
p53 is a ______ _____
Transcription factor
When there is no DNA damage, p53 normally is degraded by being tagged w/Ubiquitin by _______
MDM2
When p53 is phosphorylated, ______ cannot bind to it and cannot ubiquitinate it
MDM2
p53 increases the transcription of ______
p21
____ binds to G1/S-CdK and S-CdK inhibiting their activity
p21
T or F; Activation of G-CdK which regulates M-phase
False, M-CDK
How is M-CDK complex formed?
M-Cyclin binds to CDK-1
T or F? Both CAK and Wee1 phosphorylate M-CDK.
True
CAK adds an ______ phosphate and Wee1 adds an _______ phosphate.
Activating; inhibitory
Cdc25, once phosphorylated by _______ removes the inhibitory phosphate that Wee1 added
S-CDK
T or F? Once activated, in a positive feedback manner, M-CDK can enhance activation of more S-CDKs
False, activation of more M-CDKs
____ can phosphorylate cdc25 to enhance its activity and Wee1 to inhibit its activity
M-CDK
_____ regulates most events in M phase, such as APC activation and chromosomal segregation
M-CDK
What does active APC do to activate separase?
Ubiquitinates securin
How does APC trigger anaphase?
By ubiquitylizes securin, which cause activation of separase which then cleaves and dissociate cohesins
