how enhancers work in transcription?
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In genetics, an enhancer is a short (50–1500 bp) region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur. These proteins are usually referred to as transcription factors. ... There are hundreds of thousands of enhancers in the human genome.
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Psoralen studies in higher eukaryotes have identified that DNA supercoiling is maintained in vivo by a balance of transcription and topoisomerase activities, and that perturbation of either can cause promoter-scale and large-scale changes in DNA supercoil distribution.
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Like prokaryotic cells, eukaryotic cells also have mechanisms to prevent transcription. Transcriptional repressors can bind to promoter or enhancer regions and block transcription. Like the transcriptional activators, repressors respond to external stimuli to prevent the binding of activating transcription factors.
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Epigenetic processes, including DNA methylation and histone modification, are thought to influence gene expression chiefly at the level of transcription; however, other steps in the process (for example splicing and translation) may also be regulated epigenetically.
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intron / introns. In some genes, not all of the DNA sequence is used to make protein. Introns are noncoding sections of an RNA transcript, or the DNA encoding it, that are spliced out before the RNA molecule is translated into a protein. The sections of DNA (or RNA) that code for proteins are called exons.
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A transcriptional activator is a protein (transcription factor) that increases gene transcription of a gene or set of genes. Most activators are DNA-binding proteins that bind to enhancers or promoter-proximal elements.
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Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins). RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule. Transcription ends in a process called termination.
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Prokaryotes only carry three promoter elements, -10, -35, and the UP elements, whereas eukaryotes carry a wide variety of promoter elements (4). In addition, the use of enhancers in eukaryotic transcription allows the promoter sites in remote location on the DNA to initiate transcription.
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Eukaryotes have three RNA polymerases, not one as in bacterial cells. ... In prokaryotes, RNA polymerase by itself can initiate transcription. 4. In addition to promoters, eukaryotic genes often have extra regulatory sequences many kilobases away from the transcription start site.
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Some noncoding DNA regions, called introns, are located within protein-coding genes but are removed before a protein is made. Regulatory elements, such as enhancers, can be located in introns. Other noncoding regions are found between genes and are known as intergenic regions.
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These genes are located contiguously on a stretch of DNA and are under the control of one promoter (a short segment of DNA to which the RNA polymerase binds to initiate transcription). A single unit of messenger RNA (mRNA) is transcribed from the operon and is subsequently translated into separate proteins.
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DNA methylation regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factor(s) to DNA. During development, the pattern of DNA methylation in the genome changes as a result of a dynamic process involving both de novo DNA methylation and demethylation.
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Transcription as the production of mRNA from DNA. why is transcription necessary? mRNA formed in transcription is transported out of the nucleus, into the cytoplasm, to the ribosome (where protein synthesis takes place in the cell). Here, it directs protein synthesis.
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Prokaryotic gene expression is primarily controlled at the level of transcription. Eukaryotic gene expression is controlled at the levels of epigenetics, transcription, post-transcription, translation, and post-translation.
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Unlike prokaryotic cells, eukaryotic cells can regulate gene expression at many different levels. Eukaryotic gene expression begins with control of access to the DNA. This form of regulation, called epigenetic regulation, occurs even before transcription is initiated.
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In fact, the protein coding information in genes is interrupted by non-coding sequences called introns, which results in "split genes." The entire DNA code is faithfully transcribed into a temporary form of RNA (pre-mRNA), but this is edited in the nucleus to yield a mature mRNA.
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Regulatory proteins, such as transcription factors (TFs), protect their binding DNA sequences from nuclease cleavage, resulting in the markedly increased accessibility surrounding their binding sites and over neighboring chromatin (Hesselberth et al., 2009).