General pattern of regulatory sequences that control gene expression in eukaryotes. (a) Genes of multicellular organisms contain both promoter-proximal elements (within 200 bp of the transcription start site) and enhancers and often a TATA box (about 30 bp upstream from the start site). Enhancers may be either upstream or downstream (sometimes even within an intron of the transcribed gene) and as far away as 50 kb from the transcription start site. (b) Most yeast genes contain only one regulatory region, called an upstream activating sequence (UAS), and a TATA box which is about 100 bp upstream from the start site.