Get the answer of: Can Eukaryotic Gene Regulated by Hormones ?
Most of the hormones in human are either peptide or peptide derivatives in nature or steroid in nature. The peptide hormones do not normally enter cells because of their relatively large size. Their effects appear to be mediated by receptor proteins located in target cell membranes and also by the intracellular levels of cyclic AMP.
The steroid hormones on the other hand, are small molecules and readily enter cells through the plasma membrane. After entry the steroid hormones become tightly bound to specific receptor proteins. These receptor proteins are present only in the cytoplasm of target cells.
Following are the different views regarding the hormonal control of gene expression:
1. Some of the hormone receptor protein complexes activate transcription of target genes by binding to specific DNA sequences present in the cis-acting regulatory regions of these genes.
2. The hormone receptor protein complexes interact with specific non-histone chromosomal proteins rather than directly with DNA. This interaction would then stimulate the transcription of the correct genes.
In both the above cases hormone receptor protein complexes would function as positive regulators or activators of transcription.
3. The nonhistone chromosomal proteins play important roles in the regulation of gene expression particularly in eukaryotes.
4. The regulation of transcription in eukaryotes may well involve specific interaction among DNA, histones and non-histone chromosomal proteins.
5. The hormone receptor protein complexes activates gene expression by interacting directly with the specific DNA sequences present within the enhancer or promoter regions that regulate the transcription of the target genes.
6. Some of the steroid hormones e.g. glucocorticoid, estrogen etc. act via enhancer elements which causes localized unwinding of the two DNA strands in the promoter regions.
7. Another most striking method of hormonal control of gene expression is the selective stabilization of hormone-stimulated transcripts against cytoplasmic degradation.
Steroid hormones achieve massive accumulation of specific mRNAs by concerted manipulation of both transcriptional and post-transcriptional processes.