Rpb6 is an essential subunit in the eukaryotic polymerases Pol I, II and III. This family also contains the bacterial equivalent to Rpb6, the omega subunit. Rpb6 and omega are structurally conserved and both function in polymerase assembly .
In eukaryotes, there are three different forms of DNA-dependent RNA polymerases (EC) transcribing different sets of genes. Each class of RNA polymerase is an assemblage of ten to twelve different polypeptides. In archaebacteria, there is generally a single form of RNA polymerase which also consists of an oligomeric assemblage of 10 to 13 polypeptides. A component of 14 to 18 kDa shared by all three forms of eukaryotic RNA polymerases and which has been sequenced in budding yeast (gene RPB6 or RPO26), in Schizosaccharomyces pombe (Fission yeast) (gene rpb6 or rpo15), in human and in African swine fever virus (ASFV) is evolutionary related to the archaebacterial subunit K (gene rpoK). The archaebacterial protein is colinear with the C-terminal part of the eukaryotic subunit.
Minakhin L, Bhagat S, Brunning A, Campbell EA, Darst SA, Ebright RH, Severinov K; , Proc Natl Acad Sci U S A 2001;98:892-897.: Bacterial RNA polymerase subunit omega and eukaryotic RNA polymerase subunit RPB6 are sequence, structural, and functional homologs and promote RNA polymerase assembly. PUBMED:11158566 EPMC:11158566 .