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Modifications of p53 protein and accumulation of p21 and gadd45 mRNA in TGF-beta 1 growth inhibited cells
Y Landesman1, F Bringold, D D Milne
1Department of Molecular Genetics and Virology, Weizmann Institute of Science, Rehovot, Israel.
Abstract:
Transforming growth factory beta (TGF-beta) is a potent growth inhibitor of epithelial cells. One of the strategies used to elucidate the anti-proliferative mode of action of TGF-beta is to find out whether the receptor-generated signals interact with components of the basic machinery of the cell cycle. In this study we examined whether p53 and two other cycle inhibitory genes that can be transactivated by p53 are affected by TGF-beta 1 in epithelial cells. We show that TGF-beta 1 signalling controls the intracellular localization as well as the phosphorylation pattern and the stability of p53 protein. TGF-beta signalling also elevates the expression of p21/waf-1 and gadd45. The observed modifications in the protein suggest that p53 is involved in mediation of TGF-beta 1 growth inhibition. However, in TGF-beta 1 growth inhibited cells, wild type p53 is not required for the accumulation of the two p53 downstream targets p21/waf-1 and gadd45.
Insights
Transforming growth factor beta (TGF-β) inhibits epithelial cell proliferation. This study shows TGF-β signaling affects p53 protein stability and localization, influencing cell cycle regulators like p21/waf-1 and gadd45.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Transforming growth factor beta (TGF-β) is a key regulator of cell growth, particularly inhibiting epithelial cell proliferation.
- Understanding the molecular mechanisms of TGF-β's anti-proliferative effects is crucial for cancer research.
- Investigating the interplay between TGF-β signaling and cell cycle machinery is a key strategy to elucidate its function.
Purpose of the Study:
- To determine if TGF-β 1 signaling affects p53, a critical cell cycle regulator.
- To examine the impact of TGF-β 1 on p53's intracellular localization, phosphorylation, and stability.
- To investigate whether TGF-β 1 influences the expression of p53-responsive genes, p21/waf-1 and gadd45.
Main Methods:
- Treatment of epithelial cells with TGF-β 1.
- Analysis of p53 protein levels, phosphorylation status, and subcellular localization.
- Assessment of p21/waf-1 and gadd45 gene expression.
- Evaluation of wild-type p53's role in TGF-β 1-induced gene expression.
Main Results:
- TGF-β 1 signaling alters the intracellular localization, phosphorylation pattern, and stability of p53 protein.
- TGF-β 1 treatment leads to elevated expression of p21/waf-1 and gadd45.
- Despite p53 modifications, wild-type p53 is not essential for the accumulation of p21/waf-1 and gadd45 in TGF-β 1-treated cells.
Conclusions:
- TGF-β 1 signaling modulates p53 protein, suggesting its involvement in mediating growth inhibition.
- The accumulation of p53 downstream targets p21/waf-1 and gadd45 occurs independently of wild-type p53 in TGF-β 1-inhibited cells.
- These findings provide insights into the complex regulation of cell cycle control by TGF-β signaling in epithelial cells.