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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.
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.
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 .
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.
In the case of a repressor, the repressor protein physically obstructs the RNA polymerase from transcribing the genes. Structural genes – the genes that are co-regulated by the operon. Not always included within the operon, but important in its function is a regulatory gene, a constantly expressed gene which codes for repressor proteins. 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.
There is no lactose to inhibit the repressor, so the repressor binds to the operator, which obstructs the RNA polymerase from binding to the promoter and making lactase. Bottom: The gene is turned on. Lactose is inhibiting the repressor, allowing the RNA polymerase to bind with the promoter, and express the genes, which synthesize lactase.