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Home >>Regulation of Gene Expression - in Prokaryotes >> Gene Regulation by Hormonal Action
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Gene Regulation by Hormonal Action - Intercellular communication is a very important phenomenon in higher plants and animals. Signals originating in various glands and or secretary cells somehow stimulate target tissue or target cells to undergo dramatic changes in their metabolic patterns.

These changes frequently include altered patterns of differentiation. Peptide hormones, e.g. insulin, are large and hence do not enter into the cell. They show their effect by binding to cell surface receptors, which in turn activates the protein enzyme transcription factors by phosphorylation mechanism.

On the other hand, steroid hormones such as estrogen are small molecules, which readily enter through the plasma membrane. Once inside the target cell, they get tightly bound to specific receptor proteins, which are present only in the cytoplasm of the target cells.

The hormone receptor protein complexes activate the transcription of specific genes in two possible ways. First, the hormone receptor protein complexes interact with specific non histone chromosomal protein and this interaction stimulates the transcription of corrector protein complexes and this interaction stimulates the transcription of correct genes.

The hormone receptor protein complexes activate transcription of target genes by binding to specific DNA sequences present in the cis acting regulatory regions of genes.

Another hypothesis is that the hormone receptor protein complexes interact with specific non histone chromosomal proteins rather than directly with DNA. This interaction would then supposedly stimulate the transcription of the correct genes.
It seems likely that the non histone chromosomal proteins play an important role in the regulation of gene expression in eukaryotes.At present one cannot exclude the possibility that histone modifications or non histone chromosomal proteins are involved in some aspects of hormone regulated gene expression.
On the other hand, the evidence that is available to date strongly suggests that hormone receptor protein complexes activate gene expression by interacting directly with specific DNA sequences present within the enhancer or promoter regions that regulate the transcription of the target genes.

 
 

 
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