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 RNA polymerase I (pol I) enhancer of Saccharomyces cerevisiae contains at least three elements commonly associated with RNA polymerase II (pol II) enhancers, binding sites for the transcriptional activators general regulatory factor 2 and autonomously replicating sequence-binding factor I, and a thymidine-rich element. When the particular form of the thymidine-rich element found in the pol I enhancer was placed in front of a pol II promoter, transcription was stimulated 43-fold, comparable to the effect of a powerful pol II activator such as Gal4. Conversely, when two copies of a thymidine-rich element from a pol II enhancer were placed upstream of a pol I promoter, transcription was stimulated 38-fold. This functional reciprocity of pol I and II enhancers may reflect similarities in the mechanisms of transcriptional activation. The pol I enhancer also contains an element that appears to be pol I-specific and prevent the activation of pol II.
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PMID:Interchangeable RNA polymerase I and II enhancers. 223 33

NIH 3T3 cells infected with Moloney murine leukemia virus (MoMLV) express high levels of virus-specific RNA. To inhibit replication of the virus, we stably introduced chimeric tRNA genes encoding antisense templates into NIH 3T3 cells via a retroviral vector. Efficient expression of hybrid tRNA-MoMLV antisense transcripts and inhibition of MoMLV replication were dependent on the use of a particular type of retroviral vector, the double-copy vector, in which the chimeric tRNA gene was inserted in the 3' long terminal repeat. MoMLV replication was inhibited up to 97% in cells expressing antisense RNA corresponding to the gag gene and less than twofold in cells expressing antisense RNA corresponding to the pol gene. RNA and protein analyses suggest that inhibition was exerted at the level of translation. These results suggest that RNA polymerase III-based antisense inhibition systems can be used to inhibit highly expressed viral genes and render cells resistant to viral replication via intracellular immunization strategies.
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PMID:Expression of chimeric tRNA-driven antisense transcripts renders NIH 3T3 cells highly resistant to Moloney murine leukemia virus replication. 224 70

The transcriptional regulatory activity of the human hepatitis B virus (HBV) X-gene product was investigated. We demonstrate a new property for the HBV X-gene, the strong transcriptional trans-activation of promoters for class III genes. The stimulation of RNA polymerase III (pol III) as well as pol II promoters is shown in cells transiently transfected with the X-gene, and after its stable integration into hepatocytes. We demonstrate that X-gene containing cells stimulate the frequency of pol III transcription initiation by 20- to 40-fold, and accelerate the rate of formation of stable pol III initiation complexes in a manner indistinguishable from that of adenovirus E1a protein. Since the transcription factor TFIIIC has been shown to be limiting in the formation of stable pol III initiation complexes, template commitment experiments were performed which titrate the level of this factor in extracts. We show that X-protein containing extracts are far more efficient in forming stable pol III preinitiation complexes that cannot be competed away upon addition of a second template, indicating that TFIIIC is very probably a target of the X-protein. Thus, the HBV X-protein is apparently a member of a family of trans-activators capable of stimulating both pol II and III promoters, which includes the adenovirus E1a-protein and SV40 t antigen.
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PMID:The hepatitis B virus X-gene product trans-activates both RNA polymerase II and III promoters. 230 39

The initiation of transcription of eukaryotic genes involves the ordered assembly of a multiprotein complex on proximal promoter elements such as the TATA box. In addition to RNA polymerase II (otherwise RNA pol II, RNA polymerase B), four general transcription factors are required for initiation of transcription: BTF1 (also referred to as TFIID) which has recently been cloned from yeast, BTF2, BTF3 and STF. The first step in assembly of the initiation complex is the stable binding of BTF1 to the TATA box, which is facilitated by STF. Neither BTF2 nor BTF3 bind directly to the promoter proximal elements, but BTF3 can form a stable complex with RNA pol II. We recently purified BTF3, which is a protein of relative molecular mass 27,000, but further studies have been hampered by its low abundance in cells. On the basis of sequences from peptides of BTF3, we have now cloned two complementary DNAs, one for a protein (BTF3a) with all the characteristics of purified BTF3, and one for a shorter protein (BTF3b) lacking the first 44 residues of BTF3a and which is transcriptionally inactive, despite its ability to bind RNA pol II.
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PMID:Sequencing and expression of complementary DNA for the general transcription factor BTF3. 232 Jan 28

The murine ribosomal gene promoter contains two cis-acting control elements which operate in concert to promote efficient and accurate transcription initiation by RNA polymerase I. The start site proximal core element which is indispensable for promoter recognition by RNA polymerase I (pol I) encompasses sequences from position -39 to -1. An upstream control element (UCE) which is located between nucleotides -142 and -112 stimulates the efficiency of transcription initiation both in vivo and in vitro. Here we report the isolation and functional characterization of a specific rDNA binding protein, the transcription initiation factor TIF-IB, which specifically interacts with the core region of the mouse ribosomal RNA gene promoter. Highly purified TIF-IB complements transcriptional activity in the presence of two other essential initiation factors TIF-IA and TIF-IC. We demonstrate that the binding efficiency of purified TIF-IB to the core promoter is strongly enhanced by the presence in cis of the UCE. This positive effect of upstream sequences on TIF-IB binding is observed throughout the purification procedure suggesting that the synergistic action of the two distant promoter elements is not mediated by a protein different from TIF-IB. Increasing the distance between both control elements still facilitates stable factor binding but eliminates transcriptional activation. The results demonstrate that TIF-IB binding to the rDNA promoter is an essential early step in the assembly of a functional transcription initiation complex. The subsequent interaction of TIF-IB with other auxiliary transcription initiation factors, however, requires the correct spacing between the UCE and the core promoter element.
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PMID:Isolation and functional characterization of TIF-IB, a factor that confers promoter specificity to mouse RNA polymerase I. 232 84

In this communication we identify and initially characterize two antagonistic activities in a Xenopus oocyte extract that can modulate the in vitro transcription of RNA polymerase III (pol III) genes (5 S RNA and tRNA genes). It was found that preincubation of an inhibitory factor, referred to here as fraction I, with fractions containing TFIIIB and TFIIIC/pol III leads to the loss of a reaction's ability to support transcription. This inactivation process, which required ATP or adenylyl-imidodiphosphate (but could not use ADP), occurred only in the absence of a 5 S RNA or tRNA gene containing plasmid. Under conditions in which transcription was lost, a loss in TFIIIC's ability to specifically bind to the tRNA gene was also observed. An activity found in the "A" fraction, which was first recognized for its ability to stimulate transcription, was found to inhibit and actually reverse the observed inactivation of transcription. This activity, referred to here as fraction A2, accomplished this reactivation regardless of whether the gene was present or not, but only when a hydrolyzable form of ATP was used in the inactivation process. Transcription in an inactivated reaction could also be restored by addition of fresh transcription factors. The data presented in this paper are consistent with a model in which fraction I and fraction A2 modulate transcription through the activation and inactivation of one or more positive transcription factors.
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PMID:The identification of two antagonistic activities in a Xenopus oocyte extract that can modulate the in vitro transcription of RNA polymerase III genes. 234 67

Control of mouse ribosomal RNA synthesis in response to extracellular signals is mediated by TIF-IA, a regulatory factor whose amount or activity correlates with cell proliferation. Factor TIF-IA interacts with RNA polymerase I (pol I), thus converting it into a transcriptionally active holoenzyme, which is able to initiate specifically at the rDNA promoter in the presence of the other auxiliary transcription initiation factors, designated TIF-IB, TIF-IC and UBF. With regard to several criteria, the growth-dependent factor TIF-IA behaves like a bacterial sigma factor: (i) it associates physically with pol I, (ii) it is required for initiation of transcription, (iii) it is present in limiting amounts and (iv) under certain salt conditions, it is chromatographically separable from the polymerase. In addition, evidence is presented that dephosphorylation of pol I abolishes in vitro transcription initiation from the ribosomal gene promoter without significantly affecting the polymerizing activity of the enzyme at nonspecific templates. The involvement of both a regulatory factor and post-translational modification of the transcribing enzyme provides an efficient and versatile mechanism of rDNA transcription regulation which enables the cell to adapt ribosome synthesis rapidly to a variety of extracellular signals.
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PMID:A growth-dependent transcription initiation factor (TIF-IA) interacting with RNA polymerase I regulates mouse ribosomal RNA synthesis. 239 Sep 74

Previously we have shown that a repetitive 18 bp sequence motif, the Sal box (AGGTCGACCAGA/TT/ANTCCG), present in the 3' terminal spacer of mouse rDNA constitutes a termination signal for RNA polymerase I (pol I). Similar sequence elements which are functionally analogous to the murine terminator are present in the spacer of human rDNA. However, the human termination signal is shorter encompassing only 11 bp (GGGTCGACCAG) which correspond to the proximal part of the mouse sequence. Two out of the five human Sal box elements are functionally inactive due to natural point mutations which damage factor binding. A similar sequence motif with a 10 of 11 base identity with the downstream terminators is located upstream of the human transcription initiation site. The upstream element interacts with the same factor(s) as the downstream terminators and is also capable to stop elongating human RNA polymerase I. Despite the human and mouse factors exert different electrophoretic mobilities in gel retardation assays, UV-crosslinking and proteolytic clipping experiments indicate that both the sizes and the tertiary structure of the Sal box binding proteins of both species are very similar. When bound to DNA, both the human and the mouse factor terminate transcription of pol I from the heterologous species. The results implicate that changes in signal sequences necessary for termination have been accompanied by compensatory changes in the DNA binding domain of the protein(s) interacting with the termination signal. In contrast, the protein-protein interactions between the termination factor and the transcribing RNA polymerase I appear to have been conserved during evolution.
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PMID:An undecamer DNA sequence directs termination of human ribosomal gene transcription. 239 39

The S. cerevisiae RNA polymerase III (pol III) transcription factor TFIIIB binds to DNA upstream of the transcription start site of the SUP4 tRNA(Tyr) gene in a TFIIIC-dependent reaction and to the major 5S rRNA gene in a reaction requiring TFIIIC and TFIIIA. It is shown here that TFIIIB alone correctly positions pol III for repeated cycles of transcription on both genes, with the same efficiency as fully assembled transcription complexes. Thus, TFIIIB is the sole transcription initiation factor of S. cerevisiae pol III; TFIIIC and TFIIIA are assembly factors for TFIIIB. The TFIIIB-dependent binding of pol III to the SUP4 tRNA and 5S rRNA genes has been analyzed in binary (protein and DNA only) and precisely arrested ternary (protein, DNA, and RNA) transcription complexes. Pol III unwinds at least 14 bp of DNA at the SUP4 transcription start in a temperature-dependent process. The unwound DNA segment moves downstream with nascent RNA as a transcription bubble of approximately the same size.
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PMID:S. cerevisiae TFIIIB is the transcription initiation factor proper of RNA polymerase III, while TFIIIA and TFIIIC are assembly factors. 240 11

Reverse transcriptase of murine retroviruses is a monomeric protein of approximately 80,000 daltons, which is encoded by the central portion of the viral pol gene. To prepare large quantities of the enzyme, we have constructed gene fusions between the trpE gene and portions of the pol gene of Moloney murine leukemia virus. The inserted pol gene sequences include the entire coding region for the mature enzyme and various amounts of additional coding sequences. Many of these constructs express high levels of reverse transcriptase activity even though the NH2 and COOH termini of the protein product only approximate the correct termini of the authentic protein.
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PMID:Expression of enzymatically active reverse transcriptase in Escherichia coli. 241 Sep 10


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