Cells enter a unique intermediate 4N stage, not 4N-G1, after aborted mitosis.
It is widely accepted that mammalian cells enter the next G(1)-phase (G(1)) with 4N DNA after slippage from prolonged drug-induced mitotic block caused by activation of the transient spindle checkpoint. Understanding cell fate after mitotic slippage (MS) has significant clinical importance. The conclusion the MS cells enter 4N-G(1) is based on morphology and mitotic cyclin destruction. Definitive biochemical evidence for G(1) is scarce or unconvincing, in part because of methods of protein extraction required for immunoblot analysis that cannot take into account the cell cycle heterogeneity of cell cultures. We used single-cell-intracellular-flow-cytometric analysis to further define important factors determining cell fate after MS. Results from human and mouse embryonic stem cells (ESC) that reenter polyploid cell cycles are compared to human somatic cells that die after MS. We conclude that phosphorylation status of pRb, p53, CDK1, and especially cyclin B1 levels are important for cell fate decision in MS cells, which occur in a unique, intervening, non-G(1), tetraploid subphase.
Mantel
Charlie
C
Department of Microbiology & Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA. cmantel@iupui.edu
Guo
Ying
Y
Lee
Man Ryul
MR
Han
Myung Kwan
MK
Rhorabough
Sara
S
Kim
Kye Seong
KS
Broxmeyer
Hal E
HE
D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D053595:Embryonic Stem Cells / Q000166:cytology*; D005434:Flow Cytometry; D016193:G1 Phase / Q000502:physiology*; D006801:Humans; D051379:Mice; D008938:Mitosis / Q000502:physiology*; D010766:Phosphorylation; D016160:Retinoblastoma Protein / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
C534699:CCNB1 protein, human; C534700:Ccnb1 protein, mouse; D019926:Cyclin B; D056744:Cyclin B1; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D016203:CDC2 Protein Kinase