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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 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 ...
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.
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 ...
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 .
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1: RNA Polymerase, 2: Repressor, 3: Promoter, 4: Operator, 5: Lactose, 6: lacZ, 7: lacY, 8: lacA. Top: The gene is essentially turned off. 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 ...