Regulatory Sequences in Protein-Coding Genes
■ Expression of eukaryotic protein-coding genes generally is regulated through multiple protein-binding control regions that are located close to or distant from the start site (Figure 11-12).
■ Promoters direct binding of RNA polymerase II to DNA, determine the site of transcription initiation, and influence transcription rate.
■ Three principal types of promoter sequences have been identified in eukaryotic DNA. The TATA box, the most common, is prevalent in rapidly transcribed genes. Initiator promoters are found in some genes, and CpG islands are characteristic of genes transcribed at a low rate.
■ Promoter-proximal elements occur within =200 base pairs upstream of a start site. Several such elements, containing =10-20 base pairs, may help regulate a particular gene.
■ Enhancers, which contain multiple short control elements, may be located from 200 base pairs to tens of kilobases upstream or downstream from a promoter, within an intron, or downstream from the final exon of a gene.
■ Promoter-proximal elements and enhancers often are cell-type-specific, functioning only in specific differentiated cell types.
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