Putting It All Together: The Cell Cycle Flashcards
The cell cycle can be divided into interphase and ______________.
Mitosis
What 3 stages make up interphase?
G1
S
G2
What occurs during G1 of interphase?
Cellular contents of cell, excluding chromosomes, are duplicated
What occurs during S of interphase?
Duplication of chromosomes
What occurs during G2 of interphase
The cell “double checks” the duplication of chromosomes
Cyclin-dependent kinases (____) regulate the stages of the cell cycle.
CDKs
Cyclin-dependent kinases (CDKs) require _________ for activity.
Cyclins
In addition to cyclin binding, CDKs can be regulated by phosphorylation and ____________ (CKIs).
CDK inhibitory proteins
What are the 4 classes of cyclins?
G1
G1/S
S
G2
Each cyclin class binds and activates specific _______.
CDKs
Cyclin expression _______ and falls at distinct points in the cell cycle.
Rises
What stimulates synthesis of G1 cyclins or Cln3 in yeast?
Nutrient accumulation and availability
Cell growth
And what stimulates G1 cyclin or cyclin D synthesis in animals?
Nutrient accumulation and availability
Cell growth
Growth factor stimulation
While G1 cyclins are synthesized in response to external factors, all other cyclins are synthesized in response to the activity of the _________ CDK. Each active CDK initiates a wave of ___________ that produces the next cyclin.
Preceding
Transcription
Just as cyclins must be synthesized, so too must they be degraded. Cyclins are degradaed via ____________ after being targeted by two E3 __________ ________: the _______ complex and the ___________ complex or cyclosome.
Ubiquitin-dependent proteolysis
E3 ubiquitan ligases
SCF complex
Anaphase promoting complex or cyclosome
The SCF complex is active throughout the cell cycle, and its targets include G1 cyclins and ___________.
CDK inhibitory proteins (CKIs)
The two targets of the SCF complex are…?
G1 cyclins (e.g., Cln3 and cyclin D)
CDK inhibitory proteins (CKIs)
The SCF complexes recognizes only ___________ targets.
Phosphorylated
Unlike the SCF complex, which is active throughout the cell cycle, the APC/C is only active when phosphorylated by the M phase cyclin/CDK complex at the ______________ to metaphase transition: cyclin ___/CDK ____ in animals.
Cyclin B/CDK1
The APC/C complex is only active when phosphorylated around the anaphase to metaphase transition by the M phase cyclin/CDK complex (cyclin B/CDK1). Its targets have specific ______________ box motifs and include the S and M phase cyclins and the proteins that connect sister chromatids or cohesins.
Destruction
The S phase cyclins are cyclin E and cyclin A
The M phase cyclin is cyclin B
There are both activating and inhibiting phosphorylations of cyclin-dependent kinases. What protein facilitates activating phosphorylations of cyclin-dependent kinases?
CDK activating kinases (CAKs)
CAKs phosphorylate a ___________ residue near the active site of CDKs, which increases CDK activity but is not the _______________ step.
Threonine
Rate-limiting step
Inhibitory phosphorylations of CDKs occur at ______ and _____ residues in the ATP-binding site.
Tyrosine
Threonine
Wee1 kinases phosphorylate and inhibit which CDK of the cell cycle?
CDK1, the M phase CDK
Meanwhile cdc25 phosphatases dephosphorylate and activate _____ or the M phase CDK.
CDK1
(In yeast, CDK1, too)
There are four classes are CDK inhibitors or CKIs for each of the four types of CDKs: G1 inhibitors, G1/S inhibitors, ____ inhibitors, and M inhibitors.
S inhibitors
G1 inhibitors include ______, which binds CDK 4&6, preventing its ability to bind its cyclin, cyclin D.
INK4 (Inhibitors of kinase 4)
INK4 or G1 inhibitors of CDKs are mostly expressed in response to what?
Excessive growth stimulation
