Download Cell Division Controls in Mammalian Cells

Cell Division Controls in
Mammalian Cells
Lecture 38
BSCI 420, 412
Dec 2, 2002
“ One must show great respect to anything that divides
exponentially, no matter how small.” -Garrett Harding
1. Studies on mammalian cells in culture
2. The mammalian cell cycle control system
The results of fusion of mammalian cells at different phases
of the cell cycle:
G1,S,G2
M
M-phase nucleus
Stays in M, other
Nucleus enters
Mitosis
S contain a pos signal. G2 block to re-replication. M pos signal
Mammalian cell cycle control is more complicated than in yeasts.
At least 4 different cyclin/CdK combinations active in diff phases:
G1 (Cycling G1/S
cell) kinase (Start)
S-kinase
M-kinase
Cdk
Cycl D Kinase
Activity
CdK4
Cycl E
Cycl A
Cycl B
CdK2
CdK 1or2
CdK 1
__________________________________________________
G1
S
G2
M
The role of myc
In cell
proliferation
Initiation of DNA replication
Mcm proteins
form helicase
Each replicon
repl only once.
Phosphorylated
ORCs & Mcms
Cause block to rereplication
p-Mcms are exported
from nucleus
Activation of M-phase CdKinase (MPF)