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RNA polymerase II holoenzyme. 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. [1][2] It consists of RNA polymerase II, a subset of general transcription factors, and regulatory proteins known as SRB proteins [clarification needed].
RNA polymerase II (RNAP II and Pol II) is a multiprotein complex that transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. [1][2] It is one of the three RNAP enzymes found in the nucleus of eukaryotic cells. [3] A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase.
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that catalyzes the chemical reactions that synthesize RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the double-stranded DNA so that one strand of the exposed nucleotides can ...
The sigma factor, together with RNA polymerase, is known as the RNA polymerase holoenzyme. Every molecule of RNA polymerase holoenzyme contains exactly one sigma factor subunit, which in the model bacterium Escherichia coli is one of those listed below. The number of sigma factors varies between bacterial species.
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]
RNA polymerase core enzyme binds to the bacterial general transcription (sigma) factor to form RNA polymerase holoenzyme and then binds to a promoter. [6] (RNA polymerase is called a holoenzyme when sigma subunit is attached to the core enzyme which is consist of 2 α subunits, 1 β subunit, 1 β' subunit only).
The quaternary structure refers to the number and arrangement of the protein subunits with respect to one another. [2] Examples of proteins with quaternary structure include hemoglobin, DNA polymerase, ribosomes, antibodies, and ion channels. Enzymes composed of subunits with diverse functions are sometimes called holoenzymes, in which some ...
RNA polymerase is composed of a core and a holoenzyme structure. The core enzymes contains the catalytic properties of RNA polymerase and is made up of ββ′α2ω subunits. This sequence is conserved across all bacterial species. The holoenzyme is composed of a specific component known as the sigma factor (σ-factor). The sigma factor ...