Describe the sequence elements in eukaryotic promoters recog

Describe the sequence elements in eukaryotic promoters recognized by DNA binding proteins, and describe the proteins that bind to them and the functional signicance of such binding?

Solution

Most eukaryotic genes are controlled at the level of transcription, and the mechanisms are similar in concept to those found for bacteria. Trans-acting regulatory proteins work through sequence-specific DNA binding to their cis-acting regulatory target sequences. Near the transcription initiation site are the core promoter (the RNA polymerase II–binding region) and promoter-proximal cis-acting sequences that bind to proteins that in turn assist in the binding of RNA poly- merase II to its promoter. Additional cis-acting sequence elements can act at considerable distance—these elements are termed enhancers and silencers. Often, an enhancer or silencer element will act only in one or a few cell types in a multicellular eukaryote. The promoters, promoter-proximal elements, and distance-independent elements are all targets for binding by different trans-acting DNA-binding proteins.The core promoter usually refers to the region from the transcription start site including the TATA box, which resides approximately 30bp upstream of the transcription initiation site. This core promoter is unable to mediate efficient transcription by itself. Some important elements near the promoter, the promoter-proximal elements, are found within 100 to 200bp of the transcription initiation site. The CCAAT box functions as one of these promoter-proximal cis-acting sequences, and a GC-rich segment often functions as another.Enhancers are cis-acting sequences that can greatly increase transcription rates from promoters on the same DNA molecule; thus, they act to activate, or positively regulate, transcription. Silencers have the opposite effect. Silencers are cis-acting sequences that are bound by repressors, thereby inhibiting activators and reducing transcription. Enhancers and silencers are similar to promoter-proximal regions in that they are organized as a series of cis-acting sequences that are bound by trans-acting regulatory proteins. The core promoter, promoter-proximal elements, and distance-independent elements are all DNA sites that are recognized by sequence-specific DNA-binding proteins. The proper constellation of such trans-acting proteins is required for RNA polymerase II to initiate transcription and to achieve maximal rates of transcription.

Source: https://www.ncbi.nlm.nih.gov/books/NBK21780/