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In genetics, a promoter is a sequence of DNA to which proteins bind to initiate transcription of a single RNA transcript from the DNA downstream of the promoter. The RNA transcript may encode a protein , or can have a function in and of itself, such as tRNA or rRNA.
The RNA polymerase core associates with the sigma factor to form RNA polymerase holoenzyme. Sigma factor reduces the affinity of RNA polymerase for nonspecific DNA while increasing specificity for promoters, allowing transcription to initiate at correct sites. The core enzyme of RNA polymerase has five subunits (protein subunits) (~400 kDa). [14]
Regulatory sequence in a promoter at a transcription start site with a paused RNA polymerase and a TOP2B-induced double-strand break. Such TOP2B-induced double-strand breaks are accompanied by at least four enzymes of the non-homologous end joining (NHEJ) DNA repair pathway (DNA-PKcs, KU70, KU80 and DNA LIGASE IV) (see figure). These enzymes ...
Eukaryotic Transcription. Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of transportable complementary RNA replica. [1] Gene transcription occurs in both eukaryotic and prokaryotic cells. Unlike prokaryotic RNA polymerase that initiates the transcription of all ...
Some examples of this include producing the mRNA that encode enzymes to adapt to a change in a food source, producing the gene products involved in cell cycle specific activities, and producing the gene products responsible for cellular differentiation in multicellular eukaryotes, as studied in evolutionary developmental biology.
In prokaryotes, genes controlled by activators have promoters that are unable to strongly bind to RNA polymerase by themselves. [2] [3] Thus, activator proteins help to promote the binding of the RNA polymerase to the promoter. [2] [3] This is done through various mechanisms.
In eukaryotic cells the structure of the chromatin complex of DNA is folded in a way that functionally mimics the supercoiled state characteristic of prokaryotic DNA, so although the enhancer DNA may be far from the gene in a linear way, it is spatially close to the promoter and gene.
The genes of prokaryotes are grouped together based on similar functions into units called operons which consist of a promoter and an operator. The operator is the binding site for the repressor and thus has a function equivalent to the silencer region in Eukaryotic DNA.