Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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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)

The genes that code for 45S rRNA, the precursor of 18S, 5.8S and 28S rRNA, are transcribed by RNA polymerase I. In many eukaryotes the genes are arranged as tandem repeats in discrete chromosomal clusters. rDNA transcription and rRNA processing occur in the nucleolus. In vertebrates, at least two factors, SL-1 and UBF, specific for transcription by RNA polymerase I cooperate in the formation of the initiation complex. Interestingly, there are proteins analogous to SL-1 in unicellular eukaryotes, but the requirement for a UBF-like factor appears to vary. Recent advances in our understanding of the rDNA transcription system and its regulation have demonstrated overlap with the other nuclear transcription systems (RNA polymerase II and III). This is exemplified by the utilization of TBP as a component of SL-1 and the role of Rb in regulatory rDNA transcription.
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PMID:Transcription by RNA polymerase I. 951 85

TFIIIB, the initiation factor for transcription by RNA polymerase III (pol III) is, in yeast, composed of three subunits: TBP, TFIIIB70/Brf1 and TFIIIB90. To determine the extent to which each of these subunits is limiting for pol III transcription, the effect of overexpressing each subunit was assessed on the expression of wild-type and promoter mutant pol III genes both in vivo and in vitro . In vivo , we find that the synthesis of wild-type pol III genes is not limited to a significant extent by the level of any TFIIIB subunit. There is, however, a two-fold increase in the synthesis of the promoter mutant gene, sup9-e A19-supS1 , in strains overexpressing TFIIIB70. The findings suggest that overexpression of TFIIIB70has a differential effect on the expression of pol III genes with strong versus weak promoters. In vitro transcription assays support this conclusion and reveal an inverse correlation between the transcriptional response to TFIIIB70overexpression and promoter strength. The individual TFIIIB subunits are nuclear by immunofluorescence and are calculated to have nuclear concentrations in the low micromolar range. In comparison, the factors are diluted 100-fold or more in whole cell extracts. This dilution accounts for the generally limiting nature of TFIIIB70in pol III gene transcription in vitro.
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PMID:A differential response of wild type and mutant promoters to TFIIIB70 overexpression in vivo and in vitro. 958 Jun 84

Human TFIIB, an essential factor in transcription of protein-coding genes by RNA polymerase II, consists of an amino-terminal zinc binding domain (TFIIBn) connected by a linker of about 60 residues to a carboxy-terminal core domain (TFIIBc). The TFIIB core domain has two internally repeated motifs, each comprising five alpha-helices arranged as in the cyclin box. Compared to the crystal structure of TFIIBc in complex with TBP and a TATA-containing oligonucleotide, the NMR-derived solution structure of free TFIIBc is more compact, with a different repeat-repeat orientation and a significantly shorter first helix in the second repeat. Analysis of backbone 15N relaxation parameters indicates the presence of relatively large amplitude, nanosecond time-scale motions in the TFIIBc interrepeat linker and structural fluctuations throughout the backbone. Interaction of TFIIBc with the acidic activation domain of VP16 or with TFIIBn induces 1H-15N chemical shift and line width changes concentrated in the first repeat, interrepeat linker and the first helix of the second repeat. These results suggest that TFIIB is somewhat pliable and that the conformation of the C-terminal core domain can be modulated by interaction with the N-terminal zinc binding domain. Furthermore, binding of the VP16 activation domain may promote TFIIBc conformations primed for binding to a TBP-DNA complex.
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PMID:Human general transcription factor TFIIB: conformational variability and interaction with VP16 activation domain. 960 87

Cis -diammininedichloroplatinum(II) (cisplatin or cis -DDP) is a DNA-damaging agent that is widely used in cancer chemotherapy. Cisplatin crosslinks DNA and the resulting adducts interact with proteins that contain high-mobility-group (HMG) domains, such as UBF(upstream binding factor). UBF is a transcription factor that binds to the promoter of ribosomal RNA (rRNA) genes thereby supporting initiation of transcription by RNA polymerase I. Here we report that cisplatin causes a redistribution of UBF in the nucleolus of human cells, similar to that observed after inhibition of rRNA synthesis. A similar redistribution was observed for the major components of the rRNA transcription machinery, namely TBP, TAFIs and RNA polymerase I. Furthermore, we provide for the first time direct in vivo evidence that cisplatin blocks synthesis of rRNA, while activity of RNA polymerase II continues to be detected throughout the nucleus. The clinically ineffective trans isomer (trans -DDP) does not alter the localization of either UBF or other components of the RNA polymerase I transcription machinery. These results suggest that disruption of rRNA synthesis, which is stimulated in proliferating cells, plays an important role in the clinical success of cisplatin.
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PMID:Cisplatin inhibits synthesis of ribosomal RNA in vivo. 961 Dec 24

Transcription initiation by RNA polymerase II (RNA pol II) requires interaction between cis-acting promoter elements and trans-acting factors. The eukaryotic promoter consists of core elements, which include the TATA box and other DNA sequences that define transcription start sites, and regulatory elements, which either enhance or repress transcription in a gene-specific manner. The core promoter is the site for assembly of the transcription preinitiation complex, which includes RNA pol II and the general transcription fctors TBP, TFIIB, TFIIE, TFIIF, and TFIIH. Regulatory elements bind gene-specific factors, which affect the rate of transcription by interacting, either directly or indirectly, with components of the general transcriptional machinery. A third class of transcription factors, termed coactivators, is not required for basal transcription in vitro but often mediates activation by a broad spectrum of activators. Accordingly, coactivators are neither gene-specific nor general transcription factors, although gene-specific coactivators have been described in metazoan systems. Transcriptional repressors include both gene-specific and general factors. Similar to coactivators, general transcriptional repressors affect the expression of a broad spectrum of genes yet do not repress all genes. General repressors either act through the core transcriptional machinery or are histone related and presumably affect chromatin function. This review focuses on the global effectors of RNA polymerase II transcription in yeast, including the general transcription factors, the coactivators, and the general repressors. Emphasis is placed on the role that yeast genetics has played in identifying these factors and their associated functions.
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PMID:Molecular genetics of the RNA polymerase II general transcriptional machinery. 961 49

The basal transcription factor IIE (TFIIE) is thought to be one of the last factors to be assembled into a preinitiation complex (PIC) at eukaryotic promoters after RNA polymerase II and TFIIF have been incorporated. It was shown that a primary function of TFIIE is to recruit and cooperate with TFIIH in promoter melting. Here, we show that the large subunit of TFIIE (E56) can directly stimulate TBP binding to the promoter in the absence of other basal factors. The zinc-finger domain of E56, required for transcriptional activity, is critical for this function. In addition, the small subunit of TFIIE (E34) directly contacts DNA and TFIIA and thus providing a second mechanism for TFIIE to help binding of a TBP/IIA complex to the promoter, the first critical step in the PIC assembly. These studies suggest an alternative PIC assembly pathway in which TFIIE affects both TBP and TFIIH functions during initiation of RNA synthesis.
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PMID:An interplay between TATA box-binding protein and transcription factors IIE and IIA modulates DNA binding and transcription. 961 79

In contrast to previous findings in cell-free systems reconstituted with partially purified metazoan factors, we demonstrate dramatic activation of transcription in a TBP-dependent but TAFII-independent manner in HeLa nuclear extracts immunodepleted of TBP and major TAFIIs. Single-round transcription assays reveal that TAFII-independent activation is manifested at the level of productive preinitiation complex formation and that TAFIIs actually impair functional preinitiation complex assembly in a core promoter-specific manner. Furthermore, TAFIIs appear to elevate absolute levels of transcription under multiple-round transcription conditions, presumably by facilitating secondary initiation events. Finally, human coactivator activities related to those in yeast RNA polymerase II/mediator complexes appear to function in unfractionated HeLa nuclear extracts.
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PMID:Transcription activation via enhanced preinitiation complex assembly in a human cell-free system lacking TAFIIs. 966 Sep 76

Transcription of Xenopus ribosomal genes by RNA polymerase I is directed by a stable transcription complex that forms on the gene promoter. This complex is comprised of the HMG box factor UBF and the TBP-containing complex Rib1. Repeated sequence elements found upstream of the ribosomal gene promoter act as RNA polymerase I-specific trans-criptional enhancers. These enhancers function by increasing the probability of a stable transcription complex forming on the adjacent promoter. UBF is required for enhancer function. This role in enhancement is distinct from that at the promoter and does not involve translocation of UBF from enhancer repeats to the promoter. Here we utilize an in vitro system to demonstrate that a combination of the dimerization domain of UBF and HMG boxes 1-3 are sufficient to specify its role in enhancement. We also demonstrate that the acidic C-terminus of UBF is primarilyresponsible for its observed interaction with Rib1. Thus, we have uncoupled the Rib1 interaction and enhancer functions of UBF and can conclude that direct interaction with Rib1 is not a prerequisite for the enhancer function of UBF.
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PMID:Dimerization and HMG box domains 1-3 present in Xenopus UBF are sufficient for its role in transcriptional enhancement. 967 18

Hoechst 33342 and Hoechst 33258 bind to adenine-thymine rich regions of the minor groove of DNA. Hoechst 33342, but not Hoechst 33258, induces BC3H-1 myocyte cell death and DNA fragmentation into an internucleosomal pattern characteristics of apoptosis. Hoechst 33342 has been shown to inhibit endogenous nuclear topoisomerase I activity. Another enzymatic activity utilizing the minor groove of DNA, the initiation of RNA polymerase II activity by formation of a TATA box binding protein/TATA box promoter complex, is shown to be altered using a gel mobility shift assay. A [32P]-labeled 24-oligonucleotide containing a TATA box element formed one molecular weight complex in control and Hoechst 33258 treated cells. The presence of Hoechst 33342 (26.7 microM) decreased the amount of the control complex and increased the presence of lower molecular weight species suggesting degradation of nuclear TBP and/or release of other transcription factors from the complex creating a smaller sized molecular complex which retains TATA box binding capacity. These results suggest that the pathway utilized to induce apoptosis in BC3H-1 myocytes may also involve the alteration of normal TBP/DNA complex formation and reduction in the initiation of new transcription.
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PMID:Hoechst 33342 induces apoptosis and alters tata box binding protein/DNA complexes in nuclei from BC3H-1 myocytes. 967 78

Hypertranscription and temporal expression from the Autographa californica nuclear polyhedrosis (AcNPV) baculovirus polyhedrin promoter involves an alpha-amanitin-resistant RNA polymerase and requires a trans-acting viral factor(s). We previously reported that a 30-kDa host factor, polyhedrin promoter binding protein (PPBP), binds with unusual affinity, specificity, and stability to the transcriptionally important motif AATAAATAAGTATT within the polyhedrin (polh) initiator promoter and also displays coding strand-specific single-stranded DNA (ssDNA)-binding activity (S. Burma, B. Mukherjee, A. Jain, S. Habib, and S. E. Hasnain, J. Biol. Chem. 269:2750-2757, 1994; B. Mukherjee, S. Burma, and S. E. Hasnain, J. Biol. Chem. 270:4405-4411, 1995). We now present evidence which indicates that an additional factor(s) is involved in stabilizing PPBP-duplex promoter and PPBP-ssDNA interactions. TBP (TATA box binding protein) present in Spodoptera frugiperda (Sf9) cells is characteristically distinct from PPBP and does not interact directly with the polh promoter. Replacement of PPBP cognate sequences within the polh promoter with random nucleotides abolished PPBP binding in vitro and also failed to express the luciferase reporter gene in vivo. Phosphocellulose fractions of total nuclear extract from virus-infected cells which support in vitro transcription from the polh promoter contain PPBP activity. When PPBP was sequestered by the presence of oligonucleotides containing PPBP cognate sequence motifs, in vitro transcription of a C-free reporter cassette was affected but was restored by the exogenous addition of nuclear extract containing PPBP. When PPBP was mopped out in vivo by a plasmid carrying PPBP cognate sequence present in trans, polh promoter-driven expression of the luciferase reporter was abolished, demonstrating that binding of PPBP to the polh promoter is essential for transcription.
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PMID:The host factor polyhedrin promoter binding protein (PPBP) is involved in transcription from the baculovirus polyhedrin gene promoter. 969 45


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