4B Checkpoints Flashcards
What are the main stages of the cell cycle?
G1, S, G2, M
Includes mitosis stages
What is the purpose of checkpoints in the cell cycle?
To regulate progression and ensure conditions are met before moving to the next stage
Includes checkpoints like G1/G0, G2/M, and metaphase-to-anaphase transition
What are Cyclins?
Proteins that regulate the cell cycle by activating cyclin-dependent kinases (CDKs)
Their levels rise and fall at specific stages of the cell cycle
What are Cyclin-Dependent Kinases (CDKs)?
Enzymes that phosphorylate substrate proteins to progress through the cell cycle
CDKs act as a ‘switch’ for cell cycle progression
How do cyclins control CDK activity?
By binding to CDKs and causing phosphorylation
This binding activates CDKs and targets them to specific substrates
What is M-Cdk?
A cyclin-dependent kinase that controls the M-phase of the cell cycle
Specifically triggers chromosome condensation and the formation of the mitotic spindle
What is the role of APC/C in the cell cycle?
It facilitates the transition from metaphase to anaphase by degrading M-cyclin
Removal of M-Cdk is necessary to complete mitosis
What triggers the cell cycle checkpoints?
DNA damage, chromosomes not attached, insufficient nutrients, insufficient growth factor
These conditions can halt the cell cycle to prevent errors
Fill in the blank: Cyclin-CDK complexes act like a _______.
timer
True or False: Cyclin levels remain constant throughout the cell cycle.
False
Cyclin levels rise and fall at different stages
What are some cancer drug targets related to CDKs?
Cdk4/6
Examples include Palbociclib, Ribociclib, and Abemaciclib
What types of cancers are targeted by CDK inhibitors?
Metastatic breast cancer, pancreatic cancer, other cancers
What happens when M-Cdk is activated?
Triggers chromosome condensation and mitotic spindle formation
It starts mitosis but requires removal to finish
What is the significance of cyclin-CDK complexes in cell cycle regulation?
They ensure that stages of the cell cycle do not occur simultaneously
They also monitor conditions to ensure safe progression
What determines when’s the right time for CDks to start phosphorylation its substrates to allow a cell to progress past a checkpoint in the cell cycle??
CDKs can not act alone, they are not like other kineases. Then need to bind to another specific protein which is cyclin. There are different types of cyclin. The idea is that different cyclin are present at different stages of the cell cycle. And each one of them helps to direct CDK to not only be on but it’s going to tell it what’s substrates to phosphorylate.
So cyclin doesn’t turn on CDk only but it also bring themselves to to the right substrate for that stage of the cell cycle so they can be phosphorylated. And the cell can progress through the stage of the cell cycle.
