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Direct inhibition of the expression of cyclin D1 gene by sodium butyrate
F Lallemand1, D Courilleau, M Sabbah
1INSERM U55, Hôpital Saint Antoine, Paris, France.
Abstract:
In the mouse fibroblasts BP-A31 as well as in the human epidermoid carcinoma cells KB-3-1, both cyclin D1 mRNA and protein contents decreased rapidly during incubation with sodium butyrate. The decrease of cyclin D1 mRNA was not prevented by cycloheximide indicating that protein synthesis is not required for the inhibition of the expression of cyclin D1 gene by sodium butyrate. The 973 bp region upstream of the human cyclin D1 gene conferred inhibition of the expression of an indicator gene in transiently transfected cells. An 11 base-pair segment situated within this region, with a strong homology to the butyrate-response consensus element identified in butyrate-inducible promoters, also caused an inhibition of transcription under these conditions, indicating that cyclin D1 expression is inhibited by butyrate at the transcriptional level.
Insights
Sodium butyrate treatment significantly reduces cyclin D1 mRNA and protein levels in mouse and human cells. This inhibition occurs at the transcriptional level, independent of new protein synthesis.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Cyclin D1 is a key regulator of cell cycle progression.
- Dysregulation of cyclin D1 is implicated in various cancers.
- Sodium butyrate is a short-chain fatty acid with known biological effects.
Purpose of the Study:
- To investigate the effect of sodium butyrate on cyclin D1 expression.
- To determine the mechanism by which sodium butyrate affects cyclin D1.
- To identify regulatory elements involved in butyrate-mediated inhibition of cyclin D1.
Main Methods:
- Treatment of mouse fibroblasts (BP-A31) and human epidermoid carcinoma cells (KB-3-1) with sodium butyrate.
- Analysis of cyclin D1 mRNA and protein levels.
- Experiments with cycloheximide to assess the role of protein synthesis.
- Reporter gene assays using the upstream region of the human cyclin D1 gene.
Main Results:
- Sodium butyrate treatment led to a rapid decrease in both cyclin D1 mRNA and protein in both cell types.
- Cycloheximide did not prevent the reduction in cyclin D1 mRNA, indicating protein synthesis is not required for inhibition.
- A region upstream of the human cyclin D1 gene, containing a butyrate-response element, mediated transcriptional inhibition.
Conclusions:
- Sodium butyrate inhibits cyclin D1 expression at the transcriptional level.
- The effect of sodium butyrate on cyclin D1 is independent of new protein synthesis.
- A specific DNA sequence homologous to butyrate-response elements is involved in this transcriptional repression.