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A transcriptional activator is a protein (transcription factor) that increases transcription of a gene or set of genes. [1] 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.
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.
Figure 1. Example of a natural transcription factor up-regulating gene expression. 1. The transcription factors (labeled activator proteins) bind to their specific DNA sequence (labeled enhancers). 2. The transcription factors recruit other proteins and transcription factors to form a protein complex which binds to the gene promoter. 3.
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 ...
Thus, acetylation of histones is known to increase the expression of genes through transcription activation. Deacetylation performed by HDAC molecules has the opposite effect. By deacetylating the histone tails, the DNA becomes more tightly wrapped around the histone cores, making it harder for transcription factors to bind to the DNA.
The activator bound coactivator recruits RNA polymerase and other transcription machinery that then begins transcribing the target gene. A coactivator is a type of transcriptional coregulator that binds to an activator (a transcription factor) to increase the rate of transcription of a gene or set of genes. [1]
Illustration of an activator. In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence.
Trans-acting factors in alternative splicing in mRNA. Alternative splicing is a key mechanism that is involved in gene expression regulation. In the alternative splicing, trans-acting factors such as SR protein, hnRNP and snRNP control this mechanism by acting in trans. SR protein promotes the spliceosome assembly by interacting with snRNP(e.g. U1, U2) and splicing factors(e.g. U2AF65), and it ...