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Query: UNIPROT:P23193 (transcription elongation factor)
 739 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human RNA polymerase II is shown to be associated with a 3'-->5' exonuclease activity that removes nucleoside 5'-monophosphates from the 3' end of the transcripts in isolated ternary complexes. This activity is stimulated by SII, a protein that acts as a transcription elongation factor in vitro. In addition, we show that another transcription factor, TFIIF, stimulates a competing pyrophosphorolysis reaction. These findings raise interesting questions about the roles of these activities in vivo, including the possibility that this RNA polymerase may proofread the nascent transcript.
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PMID:Identification of a 3'-->5' exonuclease activity associated with human RNA polymerase II. 838 34

The products of the yeast CDC73 and PAF1 genes were originally identified as RNA polymerase II-associated proteins. Paf1p is a nuclear protein important for cell growth and transcriptional regulation of a subset of yeast genes. In this study we demonstrate that the product of CDC73 is a nuclear protein that interacts directly with purified RNA polymerase II in vitro. Deletion of CDC73 confers a temperature-sensitive phenotype. Combination of the cdc73 mutation with the more severe paf1 mutation does not result in an enhanced phenotype, indicating that the two proteins may function in the same cellular processes. To determine the relationship between Cdc73p and Paf1p and the recently described holoenzyme form of RNA polymerase II, we created yeast strains containing glutathione S-transferase (GST)-tagged forms of CDC73, PAF1, and TFG2 functionally replacing the chromosomal copies of the genes. Isolation of GST-tagged Cdc73p and Paf1p complexes has revealed a unique form of RNA polymerase II that contains both Cdc73p and Paf1p but lacks the Srbps found in the holoenzyme. The Cdc73p-Paf1p-RNA polymerase II-containing complex also includes Gal11p, and the general initiation factors TFIIB and TFIIF, but lacks TBP, TFIIH, and transcription elongation factor TFIIS as well as the Srbps. The Srbp-containing holoenzyme does not include either Paf1p or Cdc73p, demonstrating that these two forms of RNA polymerase II are distinct. In confirmation of the hypothesis that the two forms coexist in yeast cells, we found that a TFIIF-containing complex isolated via the GST-tagged Tfg2p construct contains both (i) the Srbps and (ii) Cdc73p and Paf1p. The Srbps and Cdc73p-Paf1p therefore appear to define two complexes with partially redundant, essential functions in the yeast cell. Using the technique of differential display, we have identified several genes whose transcripts require Cdc73p and/or Paf1p for normal levels of expression. Our analysis suggests that there are multiple RNA polymerase II-containing complexes involved in the expression of different classes of protein-coding genes.
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PMID:Cdc73p and Paf1p are found in a novel RNA polymerase II-containing complex distinct from the Srbp-containing holoenzyme. 903 43

Eukaryotic mRNA synthesis is catalyzed by multisubunit RNA polymerase II and proceeds through multiple stages referred to as preinitiation, initiation, elongation, and termination. Over the past 20 years, biochemical studies of eukaryotic mRNA synthesis have largely focused on the preinitiation and initiation stages of transcription. These studies led to the discovery of the class of general initiation factors (TFIIB, TFIID, TFIIE, TFIIF, and TFIIH), which function in intimate association with RNA polymerase II and are required for selective binding of polymerase to its promoters, formation of the open complex, and synthesis of the first few phosphodiester bonds of nascent transcripts. Recently, biochemical studies of the elongation stage of eukaryotic mRNA synthesis have led to the discovery of several cellular proteins that have properties expected of general elongation factors and that have been found to play unanticipated roles in human disease. Among these candidate general elongation factors are the positive transcription elongation factor b (P-TEFb), eleven-nineteen lysine-rich in leukemia (ELL), Cockayne syndrome complementation group B (CSB), and elongin proteins, which all function in vitro to expedite elongation by RNA polymerase II by suppressing transient pausing or premature arrest by polymerase through direct interactions with the elongation complex. Despite their similar activities in elongation, the P-TEFb, ELL, CSB, and elongin proteins appear to play roles in a diverse collection of human diseases, including human immunodeficiency virus-1 infection, acute myeloid leukemia, Cockayne syndrome, and the familial cancer predisposition syndrome von Hippel-Lindau disease. here we review our current understanding of the P-TEFb, ELL, CSB, and elongin proteins, their mechanisms of action, and their roles in human disease.
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PMID:Transcription elongation and human disease. 1087 52

The blockage of transcription elongation by RNA polymerase II (RNAPII) at DNA lesions on the transcribed strand is a serious challenge to accurate transcription. Transcription-coupled DNA repair (TCR), which is assumed to be initiated by the blockage of transcription, rapidly removes lesions on the transcribed strand of expressed genes and allows the resumption of transcription. Although helix-distorting bulky damage such as a cyclobutane pyrimidine dimer is known to block transcription elongation and to be repaired by TCR, it is not clear whether oxidative DNA lesions are repaired by TCR. First, we examined whether transcription elongation by RNAPII is stalled at sites of 2-hydroxyadenine (2-OH-A), 8-oxoadenine (8-oxoA), 8-oxoguanine (8-oxoG), or thymine glycol (Tg) on the transcribed strand. Our results indicate that RNAPII incorporated nucleotides opposite the lesions and then stalled. In addition, we found that transcription elongation factor TFIIS (SII) enabled RNAPII to bypass 8-oxoG but not the other types of damage, while transcription initiation and elongation factor TFIIF did not bypass 8-oxoG. These results suggest that SII is important for preventing cellular death due to oxidative DNA damage, assisting RNAPII to bypass 8-oxoG.
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PMID:RNA polymerase II bypasses 8-oxoguanine in the presence of transcription elongation factor TFIIS. 1737 14

The positive transcription elongation factor, P-TEFb, controls the fraction of initiated RNA polymerase II molecules that enter into the productive mode of elongation necessary to generate mRNAs. To better understand the mechanism of this transition into productive elongation we optimized a defined in vitro transcription system and compared results obtained with it to those obtained with a crude system. We found that controlling the function of TFIIF is a key aspect of RNA polymerase II elongation control. Before P-TEFb function, early elongation complexes under the control of negative factors are completely unresponsive to the robust elongation stimulatory activity of TFIIF. P-TEFb-mediated phosphorylation events, targeting the elongation complex containing DSIF and NELF, reverse the negative effect of DSIF and NELF and simultaneously facilitate the action of TFIIF. We also found that productive elongation complexes are completely resistant to negative elongation factors. Our data suggest that an additional factor(s) is involved in establishing the unique resistance activities of the elongation complexes before and after P-TEFb function. Furthermore, we provide evidence for the existence of another positive activity required for efficient function of P-TEFb. A model of the mechanism of P-TEFb-mediated elongation control is proposed in which P-TEFb induces the transition into productive elongation by changing the accessibility of elongation factors to elongation complexes. Our results have uncovered important properties of elongation complexes that allow a more complete understanding of how P-TEFb controls the elongation phases of transcription by RNA polymerase II.
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PMID:Properties of RNA polymerase II elongation complexes before and after the P-TEFb-mediated transition into productive elongation. 1754 48

The elongation phase of transcription by RNA polymerase II (RNAP II) is controlled by a carefully orchestrated series of interactions with both negative and positive factors. However, due to the limitations of current methods and techniques, not much is known about whether and how these proteins physically associate with the engaged polymerases. To gain insight into the detailed mechanisms involved, we established an experimental system for analyzing direct factor interactions to RNAP II elongation complexes on native gels, namely elongation complex electrophoretic mobility shift assay (EC-EMSA). This new assay effectively allowed detection of interactions of TFIIF, TTF2, TFIIS, DSIF and P-TEFb with elongation complexes generated from a natural promoter using an immobilized template. As an application of this assay system, we characterized the association of transcription elongation factor DSIF with RNAP II elongation complexes and discovered that the nascent transcript facilitated recruitment of DSIF. Examples of how the system can be manipulated to address different questions are provided. EC-EMSA should be useful for further investigation of factor interactions with RNAP II elongation complexes.
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PMID:Analysis of factor interactions with RNA polymerase II elongation complexes using a new electrophoretic mobility shift assay. 1883 75