Transcriptional repression in eukaryotes

Gene transcription can be controlled by positive or negative regulatory mechanisms; a combination of both is frequently responsible for the observed expression patterns. Analysis of a number of eukaryotic systems suggests that repressors can interfere with many and perhaps all the steps required for transcriptional activation. Transcriptional repression mechanisms can usefully be divided into three major classes: inhibition of DNA binding, blocking of activation and silencing.