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RNA polymerase binding in bacteria involves the sigma factor recognizing the core promoter region containing the −35 and −10 elements (located before the beginning of sequence to be transcribed) and also, at some promoters, the α subunit C-terminal domain recognizing promoter upstream elements. [12]
For transcription to take place, the enzyme that synthesizes RNA, known as RNA polymerase, must attach to the DNA near a gene.Promoters contain specific DNA sequences such as response elements that provide a secure initial binding site for RNA polymerase and for proteins called transcription factors that recruit RNA polymerase.
Transcription preinitiation complex, represented by the central cluster of proteins, causes RNA polymerase to bind to target DNA site. The PIC is able to bind both the promoter sequence near the gene to be transcribed and an enhancer sequence in a different part of the genome, allowing enhancer sequences to regulate a gene distant from it.
[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. Activators may bend the DNA in order to better expose the promoter so the RNA polymerase can bind more effectively. [3] Activators may make direct contact with the RNA polymerase and secure it to ...
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]
The DNA sequence that a transcription factor binds to is called a transcription factor-binding site or response element. [62] Transcription factors interact with their binding sites using a combination of electrostatic (of which hydrogen bonds are a special case) and Van der Waals forces. Due to the nature of these chemical interactions, most ...
A Rho factor acts on an RNA substrate. Rho's key function is its helicase activity, for which energy is provided by an RNA-dependent ATP hydrolysis. The initial binding site for Rho is an extended (~70 nucleotides, sometimes 80–100 nucleotides) single-stranded region, rich in cytosine and poor in guanine, called the rho utilisation site (rut), in the RNA being synthesised, upstream of the ...
RNA polymerase II holoenzyme is a form of eukaryotic RNA polymerase II that is recruited to the promoters of protein-coding genes in living cells. [11] It consists of RNA polymerase II, a subset of general transcription factors , and regulatory proteins known as SRB proteins.