Activator DNA-binding domains come in a variety of conformations, including the helix-turn-helix, zinc finger, and leucine zipper among others. Structure Īctivator proteins consist of two main domains: a DNA-binding domain that binds to a DNA sequence specific to the activator, and an activation domain that functions to increase gene transcription by interacting with other molecules. In some cells, usually eukaryotes, multiple activators can bind to the binding-site these activators tend to bind cooperatively and interact synergistically. Post-translational modifications to activators can also regulate activity, increasing or decreasing activity depending on the type of modification and activator being modified. Some activators have an allosteric site and can only function when a certain molecule binds to this site, essentially turning the activator on. The activity of activators can be regulated. At times, RNA polymerase can pause shortly after leaving the promoter activators also function to allow these “stalled” RNA polymerases to continue transcription. Other activators help promote gene transcription by triggering RNA polymerase to release from the promoter and proceed along the DNA. Most activators function by binding sequence-specifically to a regulatory DNA site located near a promoter and making protein–protein interactions with the general transcription machinery ( RNA polymerase and general transcription factors), thereby facilitating the binding of the general transcription machinery to the promoter. The part of the activator that makes protein–protein interactions with the general transcription machinery is referred to as an "activating region" or "activation domain". The DNA site bound by the activator is referred to as an "activator-binding site". Most activators are DNA-binding proteins that bind to enhancers or promoter-proximal elements. Activators are considered to have positive control over gene expression, as they function to promote gene transcription and, in some cases, are required for the transcription of genes to occur. Protein that increases transcription of a gene or set of genesĪ transcriptional activator is a protein ( transcription factor) that increases transcription of a gene or set of genes.
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