Explain four different ways that eukaryotic cells regulate t

Explain four different ways that eukaryotic cells regulate transcription of genes. For each method of regulation, give an example of how its regulation influences development.

Solution

Eukaryotes regulate transcription by several ways. One method is activation \'Cis and trans\' activating elements that control the activity of promoter, enhancers and transcription factors respectively.

The regulation of gene expression located on a DNA is carried out by same DNA sequences known as Cis – acting elements. Many promoters and enhancers are the examples of Cis – acting elements.

The proteins that recognize the Cis – acting elements and regulating the RNA synthesis are known as Trans – acting elements or transcription factors.

In eukaryotes, the activity promoter can be increased by Cis – acting elements called enhancers. The enhancer sequences can stimulate the promoters over a distance of several thousand base pairs. They can be located at either upstream, downstream or at the middle region of the transcribed gene. The enhancers are effective when they are located on DNA strand. The enhancers like promoters are bound to proteins and are involved in regulation of transcription.

Transcriptional control is acheived by alterations in proteins by different mechanisms. The proteins can have an effect based upon the other proteins present in the cell. This phenomenon is known as combinatorial control. Zinc – finger domain is the DNA binding domain occuring in some of the proteins. This DNA binding domain is modified to alter transcription capacity. Coactivators are the protein molecules that bind to receptor only after binding of the steroid molecules. The coactivator facilitates the activity of receptor molecules. The bromodomains present in large complexes known as chromatin – remodeling engines. These shift the location of nucleosomes.

The estrogen receptor belong to the nuclear – hormone receptor family. The receptors monitor thr gene expression basing on the hormone binding to its receptor. They contain specific DNA binding and hormone binding domains. On hormone binding they recruit the coactivators to alter the activity of RNA polymerase II to continue transcription or to stop.

When the recombinant steroid hormone receptor was prepared, the cells treated with estrogen do not activate the estrogen hormone production because the ligand binding domain belongs to progesterone and stimulate the progesterone production. When the cells are treated with progesterone, the production of estrogen is stimulated because the receptor is of the estrogen origin and the ligand that of progesterone.