A novel, non-apoptotic role for Scythe/BAT3: a functional switch between the pro- and anti-proliferative roles of p21 during the cell cycle.
Date
2012
Author
Advisors
Wang, Xiao-Fan
Chikaraishi, Dona
MacAlpine, David
Kreuzer, Kenneth
Haase, Steve
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Abstract
Scythe/BAT3 is a member of the BAG protein family whose role in apoptosis, a form
of programmed cell death, has been extensively studied. However, since the developmental
defects observed in Bat3‐null mouse embryos cannot be explained solely by defects
in apoptosis, I investigated whether BAT3 is also involved in regulating cell‐cycle
progression. Using a stable‐inducible Bat3‐knockdown cellular system, I demonstrated
that reduced BAT3 protein level causes a delay in both the G1/S transition and G2/M
progression. Concurrent with these changes in cell‐cycle progression, I observed a
reduction in the turnover and phosphorylation of the CDK inhibitor p21. p21 is best
known as an inhibitor of DNA replication; however, phosphorylated p21 has also been
shown to promote G2/M progression. Additionally, I observed that the p21 turnover
rate was also reduced in Bat3‐knockdown cells released from G2/M synchronization.
My findings indicate that in Bat3‐knockdown cells, p21 continues to be synthesized
during cell‐cycle phases that do not normally require p21, resulting in p21 protein
accumulation and a subsequent cell‐cycle delay. Finally, I showed that BAT3 co‐localizes
with p21 during the cell cycle and is required for the translocation of p21 from the
cytoplasm to the nucleus during the G1/S transition and G2/M progression. My study
reveals a novel, non‐apoptoticrole for BAT3 in cell‐cycle regulation. By maintaining
low p21 protein level during G1/S transition, BAT3 counteracts the inhibitory effect
of p21 on DNA replication and thus enables the cells to progress from G1 into S phase.
Conversely, during G2/M progression, BAT3 facilitates p21 phosphorylation, an event
that promotes G2/M progression. BAT3 modulates these pro‐ and anti‐proliferative roles
of p21 at least in part by regulating the translocation of p21 between the cytoplasm
and nucleus of the cells to ensure proper functioning and regulation of p21 in the
appropriate intracellular compartments during different cell‐cycle phases.
Type
DissertationDepartment
Molecular Cancer BiologySubject
ApoptosisBlotting, Western
Bone Neoplasms
Cell Cycle
Cell Proliferation
Cyclin-Dependent Kinase Inhibitor p21
DNA Replication
Flow Cytometry
Fluorescent Antibody Technique
Humans
Molecular Chaperones
Osteosarcoma
Phosphorylation
RNA, Small Interfering
Tumor Cells, Cultured
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https://hdl.handle.net/10161/4958Citation
Yong, Sheila T. (2012). A novel, non-apoptotic role for Scythe/BAT3: a functional switch between the pro-
and anti-proliferative roles of p21 during the cell cycle. Dissertation, Duke University. Retrieved from https://hdl.handle.net/10161/4958.Collections
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