15. Cell Cycle Regulation Flashcards
what do cells in G1 respond to
what happens if levels are sufficient?
growth factors
cell will progress into M phase
why must cyclins be degraded
to prevent the cell cycle reoccurring
this maintains unidirectionality
what cyclin is important in M-phase
cyclin B- CDK1
what cyclin is important during G2 phase
cyclin A - CDK2
what molecule is essential at regulating cell cycle transitions
cyclins
what gene is targeted via signalling to allow cyclin D and E2f expression
Myc
describe the process of mitogen dependent signalling
- cells receive mitogens from adjacent cells (paracrine signalling)
- binding of mitogen receptor activates GRB2, and Sos and eventually Ras
- Ras binding recruits a MAPK cascade
- Transcriptional activation of Myc
what type of gene is Myc
regulatory gene
what is the function of Myc
cyclin D and E2f expression
what is E2f
transcriptional regulator of S-phase genes and cyclins E and A (regulatory cyclins of S phase)
what must CDKs have to be active
their cyclin binding partner
e.g. cyclin B- cdk1
what increases catalytic efficiency of CDK
phosphorylation on T160 by CDK activating kinase (CAK)
how do CDK inhibitor proteins work
they bind to and inactivate cyclin and CDK subunits
prevents phosphorylation
what actively degrades the cyclins once their function is complete
the proteosome
what cyclin-CDK complexes regulate G1/S phase
cyclin E-CDK2
true or false:
CDK activity regulates DNA replication
true
what level of CDK activity is required for licensing
low levels of CDK
what level of CDK activity is required for DNA replication
intermediate CDK
what happens at high CDK activity levels
DNA replication is prevented fro the rest of the cell cycle
what is the function of the origin recognition complex?
binds chromatin and marks the site of potential replication
during what phase of the cell cycle is DNA replicated
S phase
what does ORC interact with when bound to chromatin
Cdc6 and Cdt1
once ORC has bound additional factors, what happens
a MCM helices binds on either side of the complex
what do the helicases do?
unwind DNA in opposite directions
how does high CDK activity prevent replication
phosphorylates ORC-Cdc6-Cdt1
this phosphorylated complex dissociates from chromatin
what happens to phosphorylated Cdt1
what is the importance of this
it is destroyed by the proteasome
allows licensing to only occur at this specific point in G1 phase
