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A corepressor downregulates (or represses) the expression of genes by binding to and activating a repressor transcription factor. The repressor in turn binds to a gene's operator sequence (segment of DNA to which a transcription factor binds to regulate gene expression), thereby blocking transcription of that gene.
Corepressor proteins also bind to the surface of the ligand binding domain of nuclear receptors, but through a LXXXIXXX(I/L) motif of amino acids (where L = leucine, I = isoleucine and X = any amino acid). [7] In addition, compressors bind preferentially to the apo (ligand free) form of the nuclear receptor (or possibly antagonist bound receptor).
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 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 ...
An implication of this is that transcription factors can regulate themselves. For example, in a negative feedback loop, the transcription factor acts as its own repressor: If the transcription factor protein binds the DNA of its own gene, it down-regulates the production of more of itself. This is one mechanism to maintain low levels of a ...
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 above mechanism of repression is a type of a feedback mechanism because it only allows transcription to occur if a certain condition is present: the presence ...
After being produced, the stability and distribution of the different transcripts is regulated (post-transcriptional regulation) by means of RNA binding protein (RBP) that control the various steps and rates controlling events such as alternative splicing, nuclear degradation (), processing, nuclear export (three alternative pathways), sequestration in P-bodies for storage or degradation and ...
corepressor – a protein that works with transcription factors to decrease the rate of gene transcription In molecular biology and genetics , transcriptional regulation is the means by which a cell regulates the conversion of DNA to RNA ( transcription ), thereby orchestrating gene activity .