Schematic representation of a typical gene locus. The promoter comprises a core promoter and a proximal promoter region, and contains binding sites for the general transcription machinery as well as specific transcription factors. Distal enhancers and silencers also provide binding sites for transcription factors, and activate or prevent the initiation of the transcription of the regulated genes. Distal enhancers and silencers would interact with the promoter through a mechanism that involves looping out the intervening DNA. Insulators act as boundaries, insuring that only the appropriate gene is transcribed.