Corepressor
Molecule that represses the expression of genes / From Wikipedia, the free encyclopedia
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 corepressor does not directly bind to DNA, but instead indirectly regulates gene expression by binding to repressors.
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.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Purple_Corepressor_Transcription_Factor_Complex_on_DNA.png/320px-Purple_Corepressor_Transcription_Factor_Complex_on_DNA.png)