A unique structure at the carboxyl terminus of the largest subunit of eukaryotic RNA polymerase II.

Abstract

Purified eukaryotic nuclear RNA polymerase II consists of three subspecies that differ in the apparent molecular masses of their largest subunit, designated Ho, Ha, and HIb for polymerase species HO, HA, and BIB, respectively. Subunits Ho, Ha, and IHb are the products of a single gene. We present here the amino acid composition of calf thymus subunits Ha and lIb and the C-terminal amino acid sequence of subunit Ha (Ho) inferred from the nucleotide sequence of part of the mouse gene encoding this RNA polymerase subunit. The calculated amino acid composition of the peptide unique to subunit Ha indicates that subunit Ha contains a domain rich in serine, proline, threonine, and tyrosine. The sequence at the 3' end of the mouse RNA polymerase H largest subunit gene reveals that the C-terminal domain consists of 52 repeats of a seven amino acid block with the consensus sequence Tyr-SerPro-Thr-Ser-Pro-Ser. This sequence is also unusual in that it contains a high percentage of potential phosphorylation sites.Eukaryotic nuclear RNA polymerases have been purified from a number of species and their complex subunit structure has been determined (1, 2). The three major classes, designated I, II, and III, differ in subunit structure and transcriptive function. Each enzyme contains from 9 to 14 subunits and has a total molecular mass of 5-6 x 105. RNA polymerases I, II, and III each contain two nonidentical large subunits (>100 kDa) and 7-12 smaller subunits. The large subunits of one class are not shared by other classes but are highly conserved within each class among different species (3-6).The only subunit that has been assigned a tentative functional role is the largest subunit of RNA polymerase II. Greenleaf and collaborators have isolated a strain of Drosophila resistant to the polymerase II inhibitor aamanitin (7). This mutation (C4) was localized to band lOC on the X chromosome and this region was cloned by P-element tagging (8,9). A 7-kilobase (kb) transcript from this region was shown to encode the largest subunit of RNA polymerase II (10). The Drosophila largest subunit gene has been crosshybridized to a number of eukaryotic DNAs (11) and has been used to clone the homologous genes from several species, including yeast (12) and mouse (unpublished data). Sequence analyses of the mouse and Drosophila clones have shown that the genes are highly conserved and are homologous to the ' subunit of Escherichia coli RNA polymerase (unpublished data), implicating the largest subunit in the processes of DNA binding and RNA chain elongation.Three different forms of RNA polymerase II have been described in a number of species. These enzymes, designated IIO, IIA, and IIB, differ in the apparent molecular masses of their largest subunit (IIo, Ha, and IIb) and appear to be related in part by limited proteolysis (13). However, anomalous mobility in NaDodSO4 gels due to postsynthetic modification cannot be ruled out. The three forms of the largest subunit Ho (240 kDa), Iha (210-220 kDa), and lIb (170-180 kDa) also differ in ...

Regulation of RNA polymerase II activity by CTD phosphorylation and cell cycle control

“…The largest subunit of RNAP II (RPB1) is unique in that it contains a carboxyl-terminal domain (CTD) consisting of multiple heptapeptide repeats with the consensus amino acid sequence YSPTSPS (Allison et al, 1985;Corden et al, 1985;Dahmus, 1996). The amino acid sequence of the repeated CTD heptapeptide has been conserved through evolution, but the number of repeats differs between species.…”

“…The amino acid sequence of the repeated CTD heptapeptide has been conserved through evolution, but the number of repeats differs between species. The RNAP II CTD contains 26 heptapeptide repeats in yeast (Allison et al, 1985), 45 in Drosophila (Allison et al, 1988;Zehring et al, 1988), and 52 in mammals (Corden et al, 1985). Several observations indicate that the CTD plays an essential role for RNAP II activity in vivo.…”

Localization of RNAPII and 3′ end formation factor CstF subunits onC. elegansgenes and operons

“…3 The CTD is composed of a seven amino acid repeat with the consensus sequence Y 1 S 2 P 3 T 4 S 5 P 6 S 7 . 4 The number of these repeats varies among species with mammals having 52 and C. elegans having 35. 5 The CTD mediates coupling of transcription with pre-mRNA processing [6][7][8][9][10] by acting as a "landing pad" for recruitment of RNA processing factors to the transcription site, 11 thus facilitating co-transcriptional pre-mRNA processing (For a review see refs.…”

Genetic identification and nucleotide sequence of the DNA polymerase gene of African swine fever virus

“…C-terminal repeats of a sequence of seven aminoacids were described in the large subunit of RNA polymerase 11 (46,47). In contrast to the RNA polymerase II tail piece, the repeated sequence of ASFV DNA polymerase does not have phosphorylation sites and is not strongly hydrophilic.…”

“…In contrast to the RNA polymerase II tail piece, the repeated sequence of ASFV DNA polymerase does not have phosphorylation sites and is not strongly hydrophilic. The role of the RNA polymerase tail piece is not known but it has been suggested that it might be involved in protein-protein interaction, in protein processing, or in competition with DNA for histone binding (46). Cellular DNA polymerases bind to DNA through zinc-finger motifs at the carboxyl end (3) and the carboxyl terminal region of herpesvirus simplex 1 DNA polymerase is essential for DNA binding and for interaction with protein UL42, an accessory protein that increases the enzyme's processivity (48).…”