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)

Adenovirus E1A proteins stimulate transcription by RNA polymerases II and III from many promoters. The detailed mechanism of transcriptional activation (transactivation) by E1A proteins remains unclear, but genetic and biochemical results suggest that E1A products might act to stimulate the activity of cellular transcription factors. In this study, a detailed mutational analysis of the adenovirus E1B promoter was undertaken to define the DNA sequences required for proper basal transcription and E1A transactivation. Two key findings emerged: first the E1B promoter is an unusually simple RNA polymerase II promoter requiring only two sequence elements for proper regulation, the TATA box and a binding site for transcription factor Sp1; and second only mutations in the TATA box interfere with E1A-transactivation, suggesting that E1A mediates its effect on this promoter through the TATA-box transcription factor.
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PMID:A TATA box implicated in E1A transcriptional activation of a simple adenovirus 2 promoter. 295 98

Saccharomyces cerevisiae contains a protein which is functionally similar to the mammalian TATA element-binding transcription factor, TFIID. The yeast factor substitutes for TFIID in a mammalian RNA polymerase II in vitro transcription system, forms a stable preinitiation complex on the Adenovirus-2 major late promoter, and binds specifically to the TATA boxes of the viral promoter and the yeast CYC1 promoter. Interestingly, the yeast factor promotes initiation at a distance from the TATA element typical of a mammalian system.
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PMID:Function of a yeast TATA element-binding protein in a mammalian transcription system. 329 Jun 87

An in vitro system for accurate transcription initiation by RNA polymerase II was developed using Ehrlich ascites tumor cells. Truncated DNA containing adenovirus 2 major late promoter was faithfully transcribed in this lysate, although the efficiency of transcription was lower than that in a HeLa cell lysate. Creatinephosphate greatly enhanced accurate transcription in this lysate. The transcriptions of various truncated mouse genes containing promoter regions in this lysate were tested, but the syntheses of run-off products were not clearly detected. Adenovirus 2 major late promoter was utilized more efficiently when integrated into circular plasmid DNA than when integrated into truncated DNA, as shown by S1 nuclease analysis.
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PMID:Accurate transcription initiation in an Ehrlich ascites tumor cell lysate. 609 90

In this review we try to examine some of the recent developments in our understanding of the mechanisms that control gene expression in eukaryotes. We discuss the nature of the positive regulation exerted by adenovirus, herpes virus or papova immediate early proteins. These proteins which can activate homologous promoters can also stimulate transcription from cellular promoters present on transfected DNA. This property of the E1a gene product of Adenovirus e.g. may be related to its immortalizing function. Transcription of cellular genes can be stimulated by viral or cellular short DNA elements named enhancers. These elements acting in cis, can be placed 5' or 3' to the gene and function in both orientations. Some of them show a remarkable cell specificity in their action. Enhancers affect the chromatin structure by creating a local nuclease sensitive region that may serve as an entry site for RNA polymerase II or for factors involved in the process of transcription initiation.
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PMID:Regulation of eukaryotic gene expression by transactivating proteins and cis acting DNA elements. 623 75

We have mapped a major initiation site of purified calf thymus RNA polymerase II in the cloned adenovirus 2 major late promoter. The specificity of this initiation site has been determined by "run-off" transcriptional analysis and by RNase T1 analysis which employs single-stranded M13 phage DNA containing the Adenovirus 2 major late promoter as probe. The TATAAA region which is used as the start site by the purified RNA polymerase II for in vitro transcription is 30 base pairs upstream from the adenovirus major late in vivo start site. The exact sequence also exists at two sites within the pBR322 plasmid but initiation does not occur at either of these sites. This indicates that the purified enzyme is not just recognizing AT-rich regions but that it is recognizing both the TATA box and its surrounding sequences. The purified RNA polymerase II transcriptional initiation site is used when transcription was carried out on either a superhelical (FI) or linear (FIII) DNA template. Selective initiation of transcription on FI DNA required (NH4)2SO4 concentrations which ranged from 90 to 150 mM. In contrast, selective initiation of transcription on FIII DNA was observed at (NH4)2SO4 concentrations that ranged from 30 to 120 mM.
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PMID:In vitro transcription initiation by purified RNA polymerase II within the adenovirus 2 major late promoter region. 632 64

Electron microscopic visualization of binary complexes between eukaryotic RNA polymerases and Adenovirus 2 (Ad 2) DNA was used to locate specific binding sites for the enzymes. RNA polymerase II from human placenta binds to 10--16 distinct sites depending on the ratio of enzyme to DNA and the divalent cation present in the binding mixture. Wheat germ RNA polymerase binds to 12--14 strong binding sites and 2--3 weaker sites, all but one of which correspond to binding sites for the placental enzyme. At least six of the strong binding sites for both enzymes correspond to promoters known to be active in vivo. As a test of the two-state model for transcription initiation, we examined binding of wheat germ RNA polymerase II to Ad 2 DNA at 0 degrees and 37 degrees. The extent of binding was the same at the two temperatures and the distributions of binary complexes were virtually identical. This observation, in conjunction with results presented previously, is strong support for the existence of I and RS complexes in eukaryotic systems.
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PMID:Location of binding sites for RNA polymerase II from wheat germ and from human placenta on adenovirus 2 DNA. 693 58

The interaction of Adenovirus 2 DNA and human placental RNA polymerase II in vitro satisfies criteria that suggest that at least some fraction of our purified polymerase preparations corresponds to prokaryotic holoenzyme and is able to initiate transcription at "true" promoters: (1) The purified enzyme forms highly stable complexes at specific sites on Ad 2 DNA; Kass = 1--2 X 10(12) M-1. (2) Transcription of Ad 2 DNA from pre-formed complexes with human RNA polymerase II is resistant to poly I. (3) Many of the stable-binding sites correspond to Ad 2 promoters known to be active in vivo. We also present evidence consistent with a two-state (I and RS) model (Chamberlin et al. 1976; Travers 1974) for the interaction of human RNA polymerase II with Ad 2 DNA. These experiments, which are similar to those described previously in studies of wheat germ RNA polymerase II (Seidman et al. 1979), indicate that the mechanisms of transcription inhibition and promoter site selection in eukaryotic and prokaryotic systems may be very similar.
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PMID:Transcription of adenovirus 2 DNA by human RNA polymerase II in vitro. 693 60

Most, though not all, of the messenger RNAs of higher cells are composed of transcripts from two or more non-contiguous DNA segments that are 'spliced' together by mechanisms which are poorly understood. There has been recent speculation that small RNA molecules may play a part in the splicing reaction, acting as templates or adaptors to stabilize the appropriate conformation of a precursor RNA. Adenovirus-2 codes for two low molecular weight RNAs, the virus-associate (VA) RNAs I and II, major and minor species, respectively. These RNAs are about 160 nucleotides long and have both been sequenced. They originate from closely spaced genes which are transcribed by RNA polymerase III, but have not been definitively associated with any function. We have shown previously that a fraction of the VA RNA of infected cells is complexed with high molecular weight RNA in a denaturation-sensitive fashion. Results presented here show that the VA RNAs bind to unfractionated late virus mRNA and to a cloned copy of a single mRNA species, but not to corresponding cloned segments of viral genomic DNA. It is suggested that VA RNA may act as a template in the splicing reaction.
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PMID:Binding of adenovirus VA RNA to mRNA: a possible role in splicing? 740 1

Adenovirus VA1 gene is efficiently transcribed by RNA polymerase III and gives rise to a small highly ordered RNA. To inhibit replication of human immunodeficiency virus (HIV), a chimeric VA1 RNA molecule was designed that contained a short antisense RNA sequence complementary to a conserved region of the HIV-1 rev encoding mRNA (28 nucleotides). This sequence, which was inserted into a projecting loop of the VA1 RNA central domain, was mainly single stranded and available for binding with its complementary sequence. The chimeric VA1 antisense was abundantly expressed in human cells constituting 3% of mRNA and promoted strong and specific inhibition of HIV-1 gene replication. The stable expression of antisense RNA in human T cells (CEM) protected these cells from HIV-1 multiplication for at least 3 months. No side effects were detected because of the lack of antisense effect upon replication of the closely related HIV-2. The VA1 gene may provide a suitably compact gene cassette for the intracellular expression of short antisense RNA directed against HIV.
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PMID:Protection of a T-cell line from human immunodeficiency virus replication by the stable expression of a short antisense RNA sequence carried by a shuttle RNA molecule. 754 Dec 91

Adenovirus E1A encodes two major proteins of 289 and 243 amino acids (289R and 243R), which both have transcription regulatory properties. E1A-289R is a transactivator whereas E1A-243R primarily functions as a repressor of transcription. Here we show that E1A repression is not restricted to RNA polymerase II genes but also includes the adenovirus virus-associated (VA) RNA genes. These genes are transcribed by RNA polymerase III and have previously been suggested to be the target of an E1A-289R-mediated transactivation. Surprisingly, we found that during transient transfection both E1A proteins repressed VA RNA transcription. E1A repression of VA RNA transcription required both conserved regions 1 and 2 and therefore differed from the E1A-mediated inhibition of simian virus 40 enhancer activity which primarily required conserved region 1. The repression was counteracted by the E1B-19K protein, which also, in the absence of E1A, enhanced the accumulation of VA RNA. Importantly, we show that efficient VA RNA transcription requires expression of both E1A and the E1B-19K protein during virus infection.
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PMID:Repression of RNA polymerase III transcription by adenovirus E1A. 851 Feb 21


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