BIOL1006 Lecture Notes - Lecture 3: Restriction Point, Growth Factor, Platelet-Derived Growth Factor

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25 Jun 2016
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Lecture 3
checkpoint - specific points where cell cycle can be put on hold
2 irreversible points - replication of genetic material, sister chromatid
separation
kinase - adds phosphate
phosphatase - takes away phosphate
phosphorylation/dephosphorylation >> activate/deactivate proteins
>> drives cell cycle
cyclin - proteins displaying characteristic patterns of
synthesis/degradation like the cell cycle
cyclin-dependent kinase (Cdk) - enzyme that controls passage
through the checkpoints
multicellular organisms respond to more external signals and use more
Cdk’s than unicellular organisms
G1/S checkpoint - main point where the cell decides whether or not
to divide
links cell division to cell growth
aka “restriction point” (R point) in animals
aka “start” in yeasts
decision to replicate genome >> decision to replicate
internal signals - nutritional cell state, cell size
external signals - factors that promote cell growth/division
G2/M checkpoint - point where cell commits to mitosis
can halt if DNA not replicated correctly
M-phase-promoting factor (MPF) - Cdk that works at this checkpoint;
sensitive to substances that disrupt DNA
removal of inhibitor phosphates acts as signal (damaged DNA >>
inhibitory phosphorylation of MPF)
spindle checkpoint – makes sure that all chromosomes attached to
spindle for anaphase
checks to see if all chromosomes are aligned on metaphase plate
anaphase-promoting complex – transmits signal that removes
inhibitors of protease (which destroys the cohesion that holds
chromatids together)
growth factors – regulatory signals that stimulate cell division
triggers intracellular signaling systems
platelet-derived growth factor (PDGF) – promotes fibroblast growth
overrides cellular controls that normally stop cell division
most cells need combination of different growth factors to totally
promote cell division
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