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In genetics and molecular biology, a corepressor is a molecule that represses the expression of genes. [1] In prokaryotes, corepressors are small molecules whereas in eukaryotes, corepressors are proteins.
In molecular biology and genetics, transcription coregulators are proteins that interact with transcription factors to either activate or repress the transcription of specific genes. [1] Transcription coregulators that activate gene transcription are referred to as coactivators while those that repress are known as corepressors .
A co-repressor is a molecule that can bind to the repressor and make it bind to the operator tightly, which decreases transcription. A repressor that binds with a co-repressor is termed an aporepressor or inactive repressor. One type of aporepressor is the trp repressor, an important metabolic protein in bacteria.
The repressor gene, lacI, will produce the repressor protein LacI which is under allosteric regulation. These genes are activated by the presence of lactose in the cell which acts as an effector molecule that binds to LacI. When the repressor is bound to lactose, it will not bind to the operator, which allows RNA polymerase to bind to the ...
If the repressor has a higher affinity for its motif than the activator, transcription would be effectively blocked in the presence of the repressor. Tight regulatory control is achieved by the highly dynamic nature of transcription factors. Again, many different mechanisms exist to control whether a transcription factor is active.
The activator, thyroid hormone receptor (TR), is bound to a corepressor preventing transcription of the target gene. The binding of a ligand hormone causes the corepressor to dissociate and a coactivator is recruited.
The ability of nuclear receptors to alternate between activation and repression in response to specific molecular cues, is now known to be attributable in large part to a diverse group of cellular factors, collectively termed coregulators and including coactivators and corepressors.
The artificial repressilator is a milestone of synthetic biology which shows that genetic regulatory networks can be designed and implemented to perform novel functions. However, it was found that the cells' oscillations drifted out of phase after a period of time and the artificial repressilator's activity was influenced by cell growth.