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Effects of retinoic acid on protein synthesis in cultured melanoma cells
Abstract:
Retinoic acid reduces the growth rate of mouse S91 melanoma cells in culture and increases the proportion of cells in the G1 phase of the cell cycle. Because of the integral role protein synthesis has been shown to play in growth control we studied the effect of retinoic acid on the protein synthesis machinery with a cell-free system developed from the melanoma cells. This system was capable of translating endogenous mRNA, exogenous globin mRNA, and the synthetic template poly(U). Of the above activities of the protein synthesis system only the translation of endogenous mRNA was reduced significantly in the cell-free system prepared from retinoic acid-treated cells. Analyses of the amount and function of RNA revealed that treatment with retinoic acid leads to reductions in total RNA content, in the proportion of ribosomes in polysomes, in the amount of poly(A)RNA, and in the amount of polysome-associated mRNA. All these effects of retinoic acid contribute to the decrease in protein synthesis activity of treated cells. Two-dimensional electrophoresis analysis of L-[35S]methionine-labeled proteins produced by untreated and treated cells revealed only a few quantitative differences. We suggest that retinoic acid-induced suppression of protein synthesis activity may be the cause for growth inhibition.
Insights
Retinoic acid slows melanoma cell growth by reducing protein synthesis. This occurs due to decreased RNA and ribosome activity, impacting cell cycle progression and overall growth.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Retinoic acid is known to influence cell growth and differentiation.
- Protein synthesis plays a critical role in regulating cell growth.
- Melanoma cell growth is a significant area of cancer research.
Purpose of the Study:
- To investigate the effect of retinoic acid on protein synthesis machinery in mouse S91 melanoma cells.
- To determine how retinoic acid impacts RNA and ribosome function related to protein synthesis.
- To elucidate the mechanism by which retinoic acid inhibits melanoma cell growth.
Main Methods:
- Developed a cell-free system from mouse S91 melanoma cells to study protein synthesis.
- Analyzed the translation of endogenous mRNA, globin mRNA, and poly(U) in the cell-free system.
- Assessed RNA content, ribosome-polysome association, poly(A)RNA levels, and polysome-associated mRNA.
- Utilized two-dimensional electrophoresis to analyze protein synthesis quantitatively.
Main Results:
- Retinoic acid significantly reduced the translation of endogenous mRNA in the cell-free system.
- Treatment with retinoic acid decreased total RNA content, polysome proportion, poly(A)RNA, and polysome-associated mRNA.
- These changes collectively led to a decrease in protein synthesis activity in treated melanoma cells.
- Quantitative differences in newly synthesized proteins were minimal between treated and untreated cells.
Conclusions:
- Retinoic acid suppresses protein synthesis activity in mouse S91 melanoma cells.
- The reduction in protein synthesis is linked to decreased RNA and ribosome function.
- This suppression of protein synthesis is proposed as the mechanism for retinoic acid-induced growth inhibition.