SCIE1106 Lecture Notes - Lecture 26: Cyclin-Dependent Kinase, Cdk Inhibitor, Programmed Cell Death
L27 Apoptosis + Caspase activity
•
Understand cell cycle phases + checkpoints
where control is exerted
•
Understand that cyclin levels oscillate with cycle
phase (the graph)
•
Understand that Cdk activity is controlled by
cyclin binding, phosphorylation and inhibitors
•
Cyclin, cyclin dependent kinase(Cdk), target
protein phosphorylation, p53 the tumour
suppressor, cell cycle checkpoints
Dividing cells must co-ordinate all aspects of their growth
• The daughter cells need all components → from
chromosomes to proteins to organelles
• DNA synthesis, organelle biosynthesis and
macromolecules biosynthesis must be tightly
controlled
o because it costs energy
Eukaryotes + its tightly regulated cell survival +
proliferation
How is it achieved?
• Like a feedback regulation, what happens
inside/outside of the cell
• This is achieved by Integrated controls that
continually evaluate the state of the cell + its
environment
o Regulation of somatic cell # is a great
example of homeostasis → this
maintains organism’s physiology within
normal limits
o Our cell is mostly somatic cells
What regulates normal cell cycle?
• Checkpoints – regulate normal cell proliferation
What is apoptosis?
• Programmed cell death
• Eliminates damaged cell
• Eliminate cells needed only temporarily during
development
What are the checkpoints associated with cell cycle
control?
1. G1/S
2. G2/M
3. Spindle assembly checkpoint (in mitsosis)
Cyclin + Cdk, cyclin dependent kinases, control passage
through the cell cycle
• Cyclins + Cdk form heterodimeric protein kinase
complex
o Ie 2 different subunits make up the active
(1) protein → cyclin + CDK
o Ase- meaning kinase, a protein, which is
an enzyme
o kinases are enzymes, they add P
groups to other proteins
• Cyclin-CDK protein complex regulate cell cycle
Which one is the catalytic subunit? (potential exam
question)
• CDK, the part that has kinase activity
• CDK is the catalytic subunit within the CDK-Cyclin
complex
• Cyclin is the regulatory subunit of this complex
• cyclin binds to CDK and activate CDK
• without cyclins, CDK are inactive
• CDK is specific, the correct cyclin needs to be
bound to activate specific CDK
• Cyclin binding determines which substrate is
phosphorylated by the kinase activity (kinase
activity is from CDK remember, not cyclin)
o When cyclin binds, it determines which
substrate the CDK phosphorylates
o CDK depends on cyclin to phosphorylate
o HENCE, cyclin dependent kinase
Cyclin regulates CDK
find more resources at oneclass.com
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Document Summary
Dividing cells must co-ordinate all aspects of their growth: the daughter cells need all components from chromosomes to proteins to organelles, dna synthesis, organelle biosynthesis and macromolecules biosynthesis must be tightly controlled, because it costs energy. Eukaryotes + its tightly regulated cell survival + proliferation. What is apoptosis? normal limits: our cell is mostly somatic cells. What regulates normal cell cycle: programmed cell death, eliminates damaged cell, eliminate cells needed only temporarily during development. Cyclin + cdk, cyclin dependent kinases, control passage through the cell cycle: cyclins + cdk form heterodimeric protein kinase complex. What are the checkpoints associated with cell cycle control: g1/s, g2/m, spindle assembly checkpoint (in mitsosis) A group of proteins that share a common evolutionary origin (no shit), reflected by similarities in function, a. a/ nt sequences and structure. Cyclin-cdk regulate cell cycle, and we talked about different cyclins/cdk and what they do, which is the regulatory subunit and which ones the catalytic subunit.
