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Transcription factors can be divided in two main categories: activators and repressors. While activators can interact directly or indirectly with the core machinery of transcription through enhancer binding, repressors predominantly recruit co-repressor complexes leading to transcriptional repression by chromatin condensation of enhancer regions.
Several cell function specific transcription factors (there are about 1,600 transcription factors in a human cell [35]) generally bind to specific motifs on an enhancer [36] and a small combination of these enhancer-bound transcription factors, when brought close to a promoter by a DNA loop, govern level of transcription of the target gene.
General transcription factors bind to the promoter. When a transcription factor is activated by a signal (here indicated as phosphorylation shown by a small red star on a transcription factor on the enhancer) the enhancer is activated and can now activate its target promoter. The active enhancer is transcribed on each strand of DNA in opposite ...
Enhancer nucleosomes can be identified by having histone 3 mono-methylated at lysine (K) 4 and acetylated at lysine (K) 27 (the single-letter abbreviation for lysine is K). [27] To free the DNA from the nucleosome, so that transcription factors can bind to their binding sites, histone 3 would also be acetylated at lysine 122 as shown in this ...
The active enhancer is transcribed on each strand of DNA in opposite directions by bound RNAP IIs. Mediator (a complex consisting of about 26 proteins in an interacting structure) communicates regulatory signals from the enhancer DNA-bound transcription factors to the promoter. NELF, in complex with DSIF and RNAP II, can pause transcription.
As a result, the enhanceosome also recruits non histone architectural transcription factors, called high-mobility group (HMG) proteins, which are responsible for regulating chromatin structure. [3] These factors do not bind to the enhancer, but instead are used to restructure the DNA to ensure that the genes can be accessed by the transcription ...
Enhancer may refer to: Enhancer (genetics), a short region of DNA that can increase transcription of a gene; Exciter (effect), audio effect unit; See also.
Any step of gene expression may be modulated, from signaling to transcription to post-translational modification of a protein. The following is a list of stages where gene expression is regulated, where the most extensively utilized point is transcription initiation, the first stage in transcription: [citation needed] Signal transduction