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Protein that binds to DNA in a manner that impacts RNA polymerase binding/recruitment.
Control of gene expression occurs via various routes within cells but one of the most efficient means is control that acts at the level of the initiation of transcription. Transcription initiation involves RNA polymerase binding to the promoter associated with a gene or operon. Transcription factors, by binding to DNA, either increase or decrease the ability of RNA polymerase to bind or otherwise catalyze transcription.
This transcription factor binding specifically occurs in the promoter or enhancer regions of a gene. By using transcription factors to control gene expression, cells can modify the expression of multiple genes simultaneously, i.e., through the production of individual transcription factors that bind to DNA in the vicinity of multiple genes. See also transcriptional regulation.
The use of transcription factors by cells as signaling molecules can be somewhat similar to use of hormones by bodies, where a given hormone can move somewhat widely about the body just as a transcription factor may move somewhat widely about the cell. There also can be multiple targets of hormones as well as multiple, different responses by the individual targets of a hormone, just as can be the case for transcription factors and their impact on the expression of different genes. Also as with hormones, not all transcription factors are so widely acting in their impact, though still can impact multiple copies of the same gene just as hormones that are limited in their impact to a single cell type can still impact multiple cells.
RNA polymerase, once bound to a promoter, can then proceed to the elongation step of transcription, that is, unless further, negative transcriptional control mechanisms exist such as repressor binding to operators, where repressor molecules themselves are examples of transcription factors.
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