cell cycle Flashcards
in which stage is the commitment point?
G1
what are cyclins?
proteins that are synthesized and degraded in a cell cycle dependent manner, control the activity of cyclin dependent kinases (activate and direct to substrate)
which cyclin is directly responsive to growth factors?
cyclin D
which cyclin-CDKs are in G1?
cyclin D-CDK4
cyclinD-CDK6
(restriction point)
cyclin E-CDK2
which cyclin-CDKs are in S?
Cyclin A- CDK2
which cyclin-CDKs are in G2?
Cyclin A-CDK1
Cyclin B-CDK1
how do cyclins activate CDKs?
cyclin binding results in conformational change that allows for APT binding and exposure of a phosphorylation site on the T loop
primary role of cyclinD-CDK4/6 complexes
inactivate Rb protein so that E2F is released
what is E2F?
replication factor that controls the expression of DNA replication enzymes as well as cyclins D, E and A
what defines the “restriction point”?
when a positive feedback loop has been set by cyclin D and growth factors are no longer required for division
which cyclin-CDK complex allows for full activation of E2F?
cyclin E-CDK2 that accumulates at the end of G1
why are high levels of E2F required for the activation of cyclin A?
cyclin A promoter only weakly binds E2F
what is responsible for “licensing” and what occurs?
cyclin E-CDK2 is responsible
assembly of complex including ORC, cdc6, cdt1 and MCM complex forms
what triggers replication in S phase?
cyclin A-CDK2 complex
what is another “term” for cyclin B-CDK1?
MPF
what controls the activity of cyclin B-CDK1?
wee1- kinase
cdc25- phosphatase
what is the action of Wee1 kinase?
adds inhibitory phosphate residue to Y15 and will stop cell from dividing if too small
what is the action of cdc25 phosphatase?
removes phosphate from Y15 allowing for division to proceed
what is the inhibitory site of CDK1? activating site?
inhibitory- Y15
activating- T161
what allows for disassembly of the nuclear envelope?
phosphorylation of lamin network
what will contribute to chromosome condensation?
condensin phosphorylation
what will trigger formation of mitotic spindle?
phosphorylation of microtubule assoc proteins
what is APC/C?
anaphase promoting complex cyclosome
what are the 2 targets of APC/C?
1- anaphase inhibitor, securin
2-cyclin B
