cell cycle review deck Flashcards
part of the cell cycle that contains the commitment point
G1
what is the effects of progesterone on dividing cells?
progesterone increased levels of MFP, MPF was noted to parallel cyclin B
actions of cyclins on CDKs (2)
- activates CDKs
- directs CDKs to specific targets in the cell
what are the “master regulators” of cell cycle progression?
cyclin-CDK complexes
how does MAP kinase relate to the cell cycle?
growth factors stimulate Ras, which activates MAP kinase pathway, which results in the stimulation of cyclin D
what stimulates cyclin D?
growth factors
what are the cyclin-CDK complexes in G1?
cyclin D-CDK4/6
cyclin E-CDK2
when is the restriction point in G1?
between cyclin D-CDK4/6 and cyclin E-CDK2
what is the cyclin-CDK complex in s?
cyclin A-CDK2
what are then cyclin-CDK complexes in G2?
cyclin A-CDK1
cyclin B- CDK1
how do cyclins activate CDKs?
- cyclin binds to CDK and allows ATP binding and exposure of P site on T loop
- t loop position change unblocks the active site
- phosphorylation on T loop by CDK-activating kinase
in G1, what initially activates cyclin d?
growth factors
what is the primary role of cyclin D-CDK4/6 complexes?
to inactivate Rb protein (tumor suppresor)
what is the role of Rb protein?
tumor suppressor that inhibits activity of E2F
what is E2F?
transcription factor that controls the expression of DNA replication enzymes cyclins D/E/A
what is established after the activation of E2F?
positive feedback loop
what is the definition of “commitment point”?
point after which growth factors are no longer required for cell division to proceed
what happens at the end of G1?
accumulation of cyclin E
what CDK does cyclin E bind?
CDK2
what is the action of cyclin E-CDK2?
fully inactivates Rb protein allowing for high levels of E2F to accumulate
what are high levels of E2F needed?
cyclin A promoter only weakly binds E2F, so high levels are needed
what else does the cyclin E-CDK2 complex accomplish?
“licenses” cell for replication through sequential assembly of pre-replication complexes (ORC, CDC6, CDT1, MCM helices)
what triggers the transition from G1-S phase?
cyclin E is degraded and CDK2 is freed to complex with cyclin A
what will activate MCM helices and recruit DNA pol?
cyclin A-CDK2 and other kinases
