In molecular biology and genetics, transcriptional regulation is a means by which cells regulate the conversion of DNA into RNA (transcription), thereby coordinating gene activity. Individual genes can be regulated in a variety of ways, from changing the number of transcribed RNA copies to the time control of gene transcription time. This control allows cells or organisms to respond to a variety of intracellular and extracellular signals to produce a response. Some examples of this include generating mRNA encoding the enzyme to adapt to changes in food sources, generating gene products involved in cell cycle-specific activity, and generating gene products responsible for cell differentiation in multicellular eukaryotes, as in evolutionary development. That's it. biology. Transcriptional regulation is an important process in all organisms. It is coordinated by transcription factors and other proteins to fine-tune the amount of RNA produced by various mechanisms. Prokaryotes and eukaryotes have completely different transcriptional control strategies, but some important features between the two are still conservative. The most important is the idea of combinatorial control that any given gene may be controlled by a specific combination of factors to control transcription. In a hypothetical example, factors A and B may regulate a different set of genes from a combination of factors A and C. This combined nature extends to complexes far beyond the two proteins and allows for a very small subset (less than 10%) of the genome to control the transcriptional process of the entire cell.
Most of the early understanding of transcription comes from prokaryotes, although the extent and complexity of transcriptional regulation is greater in eukaryotes. Prokaryotic transcription is controlled by three major sequence elements: the promoter is an element of DNA that binds to RNA polymerase and other proteins and successfully initiates transcription directly upstream of the gene. The operator recognizes repressor proteins that bind to a piece of DNA and inhibit transcription of the gene. A positive control element that binds to DNA and mobilizes higher levels of transcription. Although these methods of transcriptional regulation are also present in eukaryotes, transcription factors are significantly more complex by the number of proteins involved and the presence of introns and DNA packaging into histones. The transcription of an alkaline prokaryotic gene depends on the strength of its promoter and the presence of an activator or repressor. In the absence of other regulatory elements, the promoter-based sequence-based affinity changes to RNA polymerase result in the production of different amounts of transcripts. The variable affinity of RNA polymerase for different promoter sequences is related to the consensus sequence region upstream of the transcription initiation site. The more nucleotides the promoter has, the stronger the affinity of the promoter for RNA polymerase, consistent with the consensus sequence.
In vertebrates, most gene promoters contain CpG islands with many CpG sites. When the CpG site of the promoter of many genes is methylated, the gene becomes silent. Colorectal cancer usually has 3 to 6 drive mutations and 33 to 66 free riders or passenger mutations. However, transcriptional silencing may be more important than mutations that lead to cancer progression. For example, in colorectal cancer, about 600 to 800 genes are silenced by CpG island methylation transcription. Transcriptional repression in cancer can also occur through other epigenetic mechanisms, such as changes in the expression of microRNAs. In breast cancer, transcriptional inhibition of BRCA1 may occur more frequently by overexpression of microRNA-182 than by hypermethylation of the BRCA1 promoter.
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2. Dekker J.; et al. Exploring the three-dimensional organization of genomes: interpreting chromatin interaction data. Nat. Rev. Genet. 2013,14 (6): 390-403.