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Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We used an in vitro assay system based on HeLa cell core transcription components to examine transcript elongation by RNA polymerase II on either naked DNA or chromatin templates as a function of the three known elongation factors, IIS, TFIIF, and TFIIX. We demonstrate for the first time that mammalian RNA polymerase II can achieve physiological elongation rates on naked DNA templates in vitro. The addition of TFIIF alone gave this rate, although IIS was required to minimize the block to elongation at intrinsic termination sites. However, IIS and TFIIF provided only a slight increase in the very poor elongation efficiency of RNA polymerase II on chromatin templates. The addition of TFIIX to reactions containing IIS and TFIIF reduced the elongation rate on naked DNA templates but slightly increased the elongation efficiency on chromatin. The ability of elongation factors either separately or in combination to stimulate transcription on naked DNA and chromatin templates was also examined.
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PMID:Factor-stimulated RNA polymerase II transcribes at physiological elongation rates on naked DNA but very poorly on chromatin templates. 161 65

We have used a recently developed system that allows the isolation of complexes competent for RNA polymerase II elongation (E. Bengal, A. Goldring, and Y. Aloni, J. Biol. Chem. 264:18926-18932, 1989). Pulse-labeled transcription complexes were formed at the adenovirus major late promoter with use of HeLa cell extracts. Elongation-competent complexes were purified from most of the proteins present in the extract, as well as from loosely bound elongation factors, by high-salt gel filtration chromatography. We found that under these conditions the nascent RNA was displaced from the DNA during elongation. These column-purified complexes were used to analyze the activities of different transcription factors during elongation by RNA polymerase II. We found that transcription factor IIS (TFIIS), TFIIF, and TFIIX affected the efficiency of elongation through the adenovirus major late promoter attenuation site and a synthetic attenuation site composed of eight T residues. These factors have distinct activities that depend on whether they are added before RNA polymerase has reached the attenuation site or at the time when the polymerase is pausing at the attenuation site. TFIIS was found to have antiattenuation activity, while TFIIF and TFIIX stimulated the rate of elongation. In comparison with TFIIF, TFIIS is loosely bound to the elongation complex. We also found that the activities of the factors are dependent on the nature of the attenuator. These results indicate that at least three factors play a major role during elongation by RNA polymerase II.
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PMID:Role of the mammalian transcription factors IIF, IIS, and IIX during elongation by RNA polymerase II. 199 86

SII was purified from calf thymus tissue to apparent homogeneity by a rapid procedure. The 38-kDa protein stimulated RNA synthesis by purified calf thymus RNA polymerase II 4-fold. The calf thymus SII had similar chromatographic properties and molecular size and cross-reacted immunologically with antibodies to mouse SII (Sekimizu, K., Nakanishi, Y., Mizuno, D., and Natori, S. (1979) Biochemistry 18, 1582-1588). We have substituted the purified calf thymus SII for the partially purified HeLa transcription factor IIS fraction in a HeLa (human) transcription system reconstituted with purified factors and RNA polymerase II. The purified protein stimulated specific transcription from the adenovirus 2 major late promoter by increasing the efficiency of the elongation reaction.
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PMID:Purification and functional characterization of transcription factor SII from calf thymus. Role in RNA polymerase II elongation. 355 92

A factor that stimulates random transcription of purified DNAs by RNA polymerase II has been partially purified and analyzed with respect to its possible role in specific transcription from class II promoters. Studies of the effect of this factor (transcription factor IIS) on transcription from the adenovirus major late promoter in a system reconstituted with RNA polymerase II and purified factors (IIA, IIB, IIE, and IID) indicated that it acted subsequent to the initiation step and that it stimulated the rate of elongation. Kinetic experiments indicated that the factor affected the efficiency with which the RNA polymerase II passed through pausing sites. The relationship of transcription factor IIS to a protein previously purified from Erlich ascites tumor cells (Sekimizu, K., Nakanishi, Y., Mizuno, D., and Natori, S. (1979) Biochemistry 18, 1582-1588) was also studied.
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PMID:Factors involved in specific transcription by mammalian RNA polymerase II. Transcription factor IIS stimulates elongation of RNA chains. 381 44

A novel RNase activity was identified in a yeast RNA polymerase I (pol I) in vitro transcription system. Transcript cleavage occurred at the 3' end and was dependent on the presence of ternary pol I/DNA/RNA complexes and an additional protein factor not identical to transcription factor IIS (TFIIS). Transcript cleavage was observed both on arrested complexes at the linearized ends of the transcribed DNA and on intrinsic blocks of the DNA template. Shortened transcripts that remained associated within the ternary complexes were capable of resuming RNA chain elongation. Possible functions of the nuclease for transcript elongation or termination are discussed.
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PMID:A novel RNA polymerase I-dependent RNase activity that shortens nascent transcripts from the 3' end. 891 19

Cockayne syndrome (CS) is characterized by impaired physical and mental development. Two complementation groups, CSA and CSB, have been identified. Here we report that the CSB gene product enhances elongation by RNA polymerase II. CSB stimulated the rate of elongation on an undamaged template by a factor of about 3. A thymine-thymine cyclobutane dimer located in the template strand is known to be a strong block to transcription. Addition of CSB to the blocked polymerase resulted in addition of one nucleotide to the nascent transcript. Finally, addition of transcription factor IIS is known to cause polymerase blocked at a thymine-thymine cyclobutane dimer to digest its nascent transcript, and CSB counteracted this transcript shortening action of transcription factor IIS. Thus a deficiency in transcription elongation may contribute to the CS phenotype.
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PMID:Cockayne syndrome group B protein enhances elongation by RNA polymerase II. 932 87

We have analyzed the function of an archaeal protein (now called transcription factor S (TFS)) that shows sequence similarity to eukaryotic transcription factor IIS (TFIIS) as well as to small subunits of eukaryotic RNA polymerases I (A12.6), II (B12.2), and III (C11). Western blot analysis with antibodies against recombinant TFS demonstrated that this protein is not a subunit of the RNA polymerase. In vitro transcription experiments with paused elongation complexes at position +25 showed that TFS is able to induce cleavage activity in the archaeal RNA polymerase in a similar manner to TFIIS. In the presence of TFS, the cleavage activity of the RNA polymerase truncates the RNA back to position +15 by releasing mainly dinucleotides from the 3'-end of the nascent RNA. Furthermore, TFS reduces the amount of non-chaseable elongation complexes at position +25 as well as position +45. These findings clearly demonstrate that this protein has a similar function to eukaryotic TFIIS.
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PMID:Transcription factor S, a cleavage induction factor of the archaeal RNA polymerase. 1077 22

Transcription factor IIB (TFIIB) is an essential component in the formation of the transcription initiation complex in eucaryal and archaeal transcription. TFIIB interacts with a promoter complex containing the TATA-binding protein (TBP) to facilitate interaction with RNA polymerase II (RNA pol II) and the associated transcription factor IIF (TFIIF). TFIIB contains a zinc-binding motif near the N-terminus that is directly involved in the interaction with RNA pol II/TFIIF and plays a crucial role in selecting the transcription initiation site. The solution structure of the N-terminal residues 2-59 of human TFIIB was determined by multidimensional NMR spectroscopy. The structure consists of a nearly tetrahedral Zn(Cys)3(His)1 site confined by type I and "rubredoxin" turns, three antiparallel beta-strands, and disordered loops. The structure is similar to the reported zinc-ribbon motifs in several transcription-related proteins from archaea and eucarya, including Pyrococcus furiosus transcription factor B (PfTFB), human and yeast transcription factor IIS (TFIIS), and Thermococcus celer RNA polymerase II subunit M (TcRPOM). The zinc-ribbon structure of TFIIB, in conjunction with the biochemical analyses, suggests that residues on the beta-sheet are involved in the interaction with RNA pol II/TFIIF, while the zinc-binding site may increase the stability of the beta-sheet.
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PMID:Structure of a (Cys3His) zinc ribbon, a ubiquitous motif in archaeal and eucaryal transcription. 1104 20

We have now completed an atomic crystallographic model of the 12-subunit yeast RNA polymerase II in elongation mode, with DNA and RNA in the active-centre cleft, and the NTP substrate at the growing end of the RNA. From these studies has emerged a detailed three-dimensional view of mRNA elongation. We have extended this structural analysis to a polymerase elongation complex bound by the transcript cleavage factor TFIIS (transcription factor IIS), which is required for polymerase escape from DNA arrest sites. A detailed model of this complex reveals a single tuneable active site for RNA polymerization and cleavage, and changes in the position of the RNA and polymerase domains, reflecting the dynamic nature of the elongation complex. An additional structure of a polymerase CTD (C-terminal domain) phosphopeptide bound by the 3'-RNA processing factor Pcf11 provides insights into the coupling of transcription elongation to mRNA processing. The structure of the CTD phosphatase Scp1 trapped in an intermediary enzymatic state explains CTD dephosphorylation during recycling of the polymerase. We also recently reported the first crystal structure of a Mediator subcomplex, which reveals an extended helical fold with a conserved hinge.
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PMID:Mechanistic studies of the mRNA transcription cycle. 1662 85

Expansions of CAG repeat tracts in the germ line underlie several neurological diseases. In human patients and mouse models, CAG repeat tracts display an ongoing instability in neurons, which may exacerbate disease symptoms. It is unclear how repeats are destabilized in nondividing cells, but it cannot involve DNA replication. We showed previously that transcription through CAG repeats induces their instability (Y. Lin, V. Dion, and J. H. Wilson, Nat. Struct. Mol. Biol. 13:179-180). Here, we present a genetic analysis of the link between transcription-induced repeat instability and nucleotide excision repair (NER) in human cells. We show that short interfering RNA-mediated knockdown of CSB, a component specifically required for transcription-coupled NER (TC-NER), and knockdowns of ERCC1 and XPG, which incise DNA adjacent to damage, stabilize CAG repeat tracts. These results suggest that TC-NER is involved in the pathway for transcription-induced CAG repeat instability. In contrast, knockdowns of OGG1 and APEX1, key components involved in base excision repair, did not affect repeat instability. In addition, repeats are stabilized by knockdown of transcription factor IIS, consistent with a requirement for RNA polymerase II (RNAPII) to backtrack from a transcription block. Repeats also are stabilized by knockdown of either BRCA1 or BARD1, which together function as an E3 ligase that can ubiquitinate arrested RNAPII. Treatment with the proteasome inhibitor MG132, which stabilizes repeats, confirms proteasome involvement. We integrate these observations into a tentative pathway for transcription-induced CAG repeat instability that can account for the contractions observed here and potentially for the contractions and expansions seen with human diseases.
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PMID:Transcription-induced CAG repeat contraction in human cells is mediated in part by transcription-coupled nucleotide excision repair. 1759 97


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