RPOLDRNA polymerases D
|SMART accession number:||SM00662|
|Description:||DNA-directed RNA polymerase subunit D and bacterial alpha chain|
|Interpro abstract (IPR011263):|
DNA-directed RNA polymerases EC 18.104.22.168 (also known as DNA-dependent RNA polymerases) are responsible for the polymerisation of ribonucleotides into a sequence complementary to the template DNA. In eukaryotes, there are three different forms of DNA-directed RNA polymerases transcribing different sets of genes. Most RNA polymerases are multimeric enzymes and are composed of a variable number of subunits. The core RNA polymerase complex consists of five subunits (two alpha, one beta, one beta-prime and one omega) and is sufficient for transcription elongation and termination but is unable to initiate transcription. Transcription initiation from promoter elements requires a sixth, dissociable subunit called a sigma factor, which reversibly associates with the core RNA polymerase complex to form a holoenzyme [(PUBMED:3052291)]. The core RNA polymerase complex forms a "crab claw"-like structure with an internal channel running along the full length [(PUBMED:10499798)]. The key functional sites of the enzyme, as defined by mutational and cross-linking analysis, are located on the inner wall of this channel.
RNA synthesis follows after the attachment of RNA polymerase to a specific site, the promoter, on the template DNA strand. The RNA synthesis process continues until a termination sequence is reached. The RNA product, which is synthesised in the 5' to 3'direction, is known as the primary transcript. Eukaryotic nuclei contain three distinct types of RNA polymerases that differ in the RNA they synthesise:
The core of the bacterial RNA polymerase (RNAP) consists of four subunits, two alpha, a beta and a beta', which are conserved from bacteria to mammals. The alpha subunit (RpoA) initiates RNAP assembly by dimerising to form a platform on which the beta subunits can interact, and plays a direct role in promoter recognition [(PUBMED:10972792)]. In eukaryotes, RNA polymerase (RNAP) II is responsible for all mRNA synthesis. RNAP-II consists of 12 subunits, where subunits Rpb3 and Rpb11 form a heterodimer that is functionally analogous to the bacterial RpoA homodimer [(PUBMED:12860379)]. Archaeal RNAP closely resembles eukaryotic RNAP-II, and is composed of 12 subunits, of which D and L form a heterodimer resembling the Rpb3/Rpb11 and RpoA/RpoA dimers [(PUBMED:12694606)].
The bacterial RpoA, eukaryotic Rpb3 and archaeal D subunits share sequence and structural motifs, and can be placed into a single family. These subunits also have unique sequence motifs, especially at their C-terminal ends, which are involved in promoter specificity, for example the CTD of the bacterial RNAP alpha subunit (IPR011260).
|GO process:||transcription, DNA-dependent (GO:0006351)|
|GO function:||DNA-directed RNA polymerase activity (GO:0003899)|
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