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Regulatory elements in the first intron of the mouse Ha-ras gene
J B Telliez1, M Plumb, A Balmain
1INSERM Unite 124, Institut de Recherches sur le Cancer de Lille, France.
Abstract:
The Ha-ras gene is one of the three oncogenes (Ha-ras, Ki-ras, and N-ras) of the ras superfamily of small G proteins. The p21ras proteins encoded by the ras genes are key proteins involved in the transduction of signals from membrane receptor-tyrosine kinases to downstream targets. The ras genes seem to play a ubiquitous role in the control of cell proliferation and cell differentiation. At the same time, ras genes may perform specific differentiated functions in certain cell types. Little is known about the regulation of expression of the Ha-ras gene. The first intron of the Ha-ras gene has been reported to be highly conserved between human and rodent. We investigated the role that this intron may play in the regulation of expression of Ha-ras. The promoter region of the Ha-ras gene exhibits characteristics of a housekeeping gene. Deletion analysis shows the existence of an enhancer-type element in the 5' region of the first intron (intron 0). DNase 1 footprinting experiments reveal five sites that interact with nuclear proteins from fibroblast and epithelial cell lines. Deletion and site-directed mutagenesis of three of these sites show that two are involved in a positive effect and one in a negative effect on the regulation of expression of the mouse Ha-ras gene.
Insights
The Ha-ras gene
Area of Science:
- Molecular Biology
- Oncogenes
- Gene Regulation
Background:
- The Ha-ras gene is part of the ras superfamily, encoding p21ras proteins crucial for signal transduction.
- Ras genes regulate cell proliferation and differentiation, but Ha-ras expression regulation is poorly understood.
- The first intron of Ha-ras is conserved across species, suggesting a regulatory role.
Purpose of the Study:
- To investigate the regulatory role of the first intron of the Ha-ras gene in gene expression.
- To identify specific elements within the Ha-ras first intron that control its expression.
Main Methods:
- Deletion analysis of the Ha-ras promoter and first intron.
- DNase 1 footprinting to identify nuclear protein binding sites.
- Site-directed mutagenesis to assess the function of identified regulatory sites.
Main Results:
- An enhancer-type element was identified in the 5' region of the Ha-ras first intron.
- Five nuclear protein binding sites within the intron were detected.
- Mutagenesis revealed two positive and one negative regulatory sites within the intron.
Conclusions:
- The first intron of the Ha-ras gene contains regulatory elements that modulate its expression.
- These findings contribute to understanding the complex regulation of Ha-ras oncogene expression.