c-Rel arrests the proliferation of HeLa cells and affects critical regulators of the G1/S-phase transition
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1Center for Advanced Biotechnology and Medicine, and Graduate Program in Microbiology and Molecular Genetics, Rutgers University, Piscataway, New Jersey 08854, USA.
Abstract:
A tetracycline-regulated system was used to characterize the effects of c-Rel on cell proliferation. The expression of c-Rel in HeLa cells led to growth arrest at the G1/S-phase transition, which correlated with its nuclear localization and the induction of endogenous IkappaB alpha expression. These changes were accompanied by a decrease in E2F DNA binding and the accumulation of the hypophosphorylated form of Rb. In vitro kinase assays showed a reduction in Cdk2 kinase activity that correlated with elevated levels of p21WAF1 Cdk inhibitor and p53 tumor suppressor protein. While the steady-state levels of WAF1 transcripts were increased, pulse-chase analysis revealed a sharp increase in p53 protein stability. Importantly, the deletion of the C-terminal transactivation domains of c-Rel abolished these effects. Together, these studies demonstrate that c-Rel can affect cell cycle control and suggest the involvement of the p21WAF1 and p53 cell cycle regulators.
Insights
The transcription factor c-Rel halts cell proliferation by arresting the cell cycle at G1/S. This involves regulating p21WAF1 and p53, crucial for cell cycle control.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- The transcription factor c-Rel plays a role in various cellular processes, including cell proliferation and survival.
- Understanding the precise mechanisms by which c-Rel influences the cell cycle is crucial for cancer research.
Purpose of the Study:
- To investigate the effects of c-Rel expression on cell proliferation and cell cycle progression.
- To elucidate the molecular pathways and regulators involved in c-Rel-mediated cell cycle control.
Main Methods:
- Utilized a tetracycline-regulated system for controlled c-Rel expression in HeLa cells.
- Performed cell cycle analysis (G1/S-phase transition), nuclear localization studies, and Western blotting.
- Conducted in vitro kinase assays, E2F DNA binding assays, and analyzed protein stability (pulse-chase).
Main Results:
- c-Rel expression induced G1/S-phase growth arrest, correlating with nuclear localization and increased IkappaB alpha.
- Observed decreased E2F DNA binding, accumulation of hypophosphorylated Rb, and reduced Cdk2 kinase activity.
- Elevated p21WAF1 and p53 levels, increased p53 protein stability, and abolished effects upon deletion of c-Rel transactivation domains.
Conclusions:
- c-Rel significantly impacts cell cycle control, leading to growth arrest.
- The p21WAF1 and p53 cell cycle regulators are implicated in mediating c-Rel's effects on cell proliferation.
- The C-terminal transactivation domains of c-Rel are essential for its cell cycle regulatory functions.