Lecture 21 Flashcards
(8 cards)
Cell cycle Restriction Point occurs in ____ (phase) and _____ (growth factors) are required to pass this point. Without these growth factors, the cell enters ____ (phase).
G1
Mitogens
G0
_____/_____ complexes drive the progression of the cell cycle from phase to phase. The _____ enzyme is active when cell-cycle stage-specific ______ bind and it undergoes activating ________ as well as removal of inhibitory _______. _____ can bind and inactivate what would otherwise be an active complex. ______ is the principal mechanism for degrading _____ (which are marked by ______ and ubiquitinated) and plays a major role in transitioning from one stage to the next in the cell cycle.
Cyclin/CDK
CDK
Cyclins
Phosphorylation
Phosphorylation
CDKI
Proteolysis
Cyclins
Phosphorylation
To initiate normal proliferation, a cell needs growth factors to bind ______, which activate tranducers (e.g. ____), which in turn activate ______ factors.
RTKs
Ras
Transcription factors
When ____ is hypophosphorylated (which occurs in ___ phase), it binds ____, a transcription factor necessary for the expression of G1/S CDK. G1 CDK phosphorylates ____, and it unbinds ____, allowing it to induce expression of G1/S CDK, which also phosphorylates _____. Hyperphosphorylation of ____ is key to overcoming Restriction Point and moving the cell into S phase.
RB
M
EF2
RB
EF2
RB
RB
In S phase, DNA replication cannot occur until loaded _____ is activated via phosphorylation by _____ CDK.
Helicase
G1/S CDK
DNA damage will cause the cell cycle to arrest in either ____ or ____ phases. Improper spindle attachment will cause cell cycle arrest in _____ phase. Incomplete DNA replication will cause the cell to arrest in ____ phase.
G1
G2
M
S
An example of DNA damage that leads to cell cycle arrest is double stranded breaks. These are detected by ____ which activates the checkpoint kinase ____, which then activates ____, which in turn activates a CDKI (___). Remember what CDKI function is…so if it inhibits its target, no phosphorylation of what?
ATM
CHK2
p53
p21
No phosphorylation of RB –> stays bound to and sequesters EF2 –> cell arrested in G1.
_____ recognizes SINGLE stranded gaps in DNA and activates the checkpoint kinase ____ which inhibits a dephosphorylase (CDC25C) whose function is to remove the _____ phosphorylation on CDK1.
ATR
CHK1
Inhibitory
