Rpb5 has a bipartite structure which includes a eukaryote-specific N-terminal domain and a C-terminal domain resembling the archaeal RNAP subunit H [1,2]. The N-terminal domain is involved in DNA binding and is part of the jaw module in the RNA pol II structure . This module is important for positioning the downstream DNA.
Prokaryotes contain a single DNA-dependent RNA polymerase (RNAP; EC) that is responsible for the transcription of all genes, while eukaryotes have three classes of RNAPs (I-III) that transcribe different sets of genes. Each class of RNA polymerase is an assemblage of ten to twelve different polypeptides. Certain subunits of RNAPs, including RPB5 (POLR2E in mammals), are common to all three eukaryotic polymerases. RPB5 plays a role in the transcription activation process. Eukaryotic RPB5 has a bipartite structure consisting of a unique N-terminal region, plus a C-terminal region that is structurally homologous to the prokaryotic RPB5 homologue, subunit H (gene rpoH) (INTERPRO) [PUBMED:10841538, PUBMED:10191143, PUBMED:1729711, PUBMED:10841537].
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