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p53-independent anisomycin induced G1 arrest and apoptosis in L1210 cell lines
1Department of Biochemistry, East Carolina University, School of Medicine, Greenville, NC 27858-4354, USA.
Abstract:
An L1210 cell line selected for resistance to deoxyadenosine (Y8) has been shown to have barely detectable levels of p53 mRNA and no measurable p53 protein in comparison to the parental mouse wild-type (WT) L1210 cells. We now show that the protein synthesis inhibitors, anisomycin and cycloheximide, arrest WT cells in the G1 phase of the cell cycle and induce apoptosis in Y8 cells via a p53-independent mechanism. There was a decrease in Rb phosphorylation but without the induction of WAF1 protein. Anisomycin treatment activated NF kappa B in the WT cells as early as 0.5 hr after treatment but did not activate NF kappa B in the Y8 cells. Cycloheximide was neither as potent as anisomycin in arresting WT cells at G1 and inducing apoptosis in Y8 cells, nor as potent in decreasing Rb phosphorylation. The finding that caffeine could override the G1 arrest induced by anisomycin and cycloheximide in the WT cells further supports the idea that the effects of anisomycin or cycloheximide on the cell cycle are at the level of cell cycle regulation, and are likely not mediated exclusively through the inhibition of protein synthesis.
Insights
Protein synthesis inhibitors like anisomycin and cycloheximide affect cell cycle regulation. These compounds induce apoptosis in resistant L1210 cells (Y8) through a p53-independent pathway, impacting cell cycle arrest and Rb phosphorylation.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- The L1210 cell line, when selected for resistance to deoxyadenosine (Y8), exhibits significantly reduced p53 mRNA and protein levels compared to wild-type (WT) L1210 cells.
- Understanding the mechanisms of cell cycle regulation and apoptosis is crucial in cancer research.
Purpose of the Study:
- To investigate the effects of protein synthesis inhibitors (anisomycin and cycloheximide) on WT and Y8 L1210 cells.
- To determine if these effects are mediated by the p53 pathway.
- To explore the role of cell cycle regulators like Rb and NF-kappa B.
Main Methods:
- Treatment of WT and Y8 L1210 cells with anisomycin and cycloheximide.
- Analysis of cell cycle arrest (G1 phase) and apoptosis induction.
- Assessment of Rb phosphorylation and WAF1 protein levels.
- Evaluation of NF-kappa B activation.
- Investigation of caffeine's effect on cell cycle arrest.
Main Results:
- Anisomycin and cycloheximide induced G1 arrest in WT cells and apoptosis in Y8 cells via a p53-independent mechanism.
- A decrease in Rb phosphorylation was observed, but WAF1 protein was not induced.
- Anisomycin activated NF-kappa B in WT cells but not in Y8 cells.
- Cycloheximide was less potent than anisomycin in cell cycle arrest, apoptosis induction, and decreasing Rb phosphorylation.
- Caffeine reversed the G1 arrest induced by these inhibitors in WT cells.
Conclusions:
- The effects of anisomycin and cycloheximide on cell cycle regulation and apoptosis in L1210 cells are p53-independent.
- These inhibitors likely act on cell cycle regulatory mechanisms rather than solely through protein synthesis inhibition.
- NF-kappa B activation is involved in the response to anisomycin in WT cells.