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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)
