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)

Faithful and efficient transcription initiation at the mouse ribosomal gene promoter requires besides RNA polymerase I (pol I) four polypeptide trans-acting factors, termed TIF-IA, TIF-IB, TIF-IC, and mUBF. We have partially purified these proteins from cultured Ehrlich ascites cells and show that in the presence of TIF-IA and TIF-IB, pol I directs very low amounts of specific transcripts. Neither TIF-IC nor mUBF on their own significantly stimulate the efficiency of template utilization. However, both factors together strongly activate transcription. Interestingly, factor TIF-IB - the murine homologue of human SL1 - fails to program a human extract to transcribe the murine template, but requires its homologous RNA polymerase I. This finding implicates that not only some rDNA transcription factors but also pol I exhibits species-specific differences. The growth-related factor TIF-IA, on the other hand, stimulates both mouse and human rDNA transcription. This regulatory factor whose amount or activity fluctuates according to the proliferation rate of the cells, is functionally inactivated by antibodies against cdc2 protein kinase. This result together with the observation that transcription is stimulated by ATP-gamma S, an ATP analogue which is a substrate for protein kinases but not for protein phosphatases, strongly suggests that post-translational protein modification is involved in rDNA transcription regulation.
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PMID:Trans-acting factors involved in species-specificity and control of mouse ribosomal gene transcription. 192 92

RNA polymerase II lacking the fourth and seventh largest subunits (pol II delta 4/7) was purified from Saccharomyces cerevisiae strain rpb-4, in which the gene for the fourth largest subunit is deleted. pol II delta 4/7 was indistinguishable from wild-type pol II (holoenzyme) in promoter-independent initiation/chain elongation activity (400-800 nmol of nucleotide incorporated/10 min/mg of protein at 22 degrees C), in rate of chain elongation (20-25 nucleotides/s), and in the recognition of pause sites in the DNA template. In contrast to pol II holoenzyme, pol II delta 4/7 was inactive in promoter-directed initiation of transcription in vitro. The addition of an equimolar complex of the fourth and seventh largest subunits, purified from pol II holoenzyme by ion-exchange chromatography in the presence of urea, restored promoter-directed initiation activity to pol II delta 4/7. The transcriptional activator protein Gal4-VP16 could also elicit promoter-directed initiation by pol II delta 4/7 from a promoter with a Gal4 binding site. Complementation was observed between extracts of strain rpb-4, lacking the fourth largest subunit, and strain Y260-1, with a defect in the largest subunit. These extracts were individually inactive, but a mixture would support promoter-directed initiation. The fourth and seventh largest subunits may, therefore, shuttle between polymerase molecules.
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PMID:Two dissociable subunits of yeast RNA polymerase II stimulate the initiation of transcription at a promoter in vitro. 198 24

Fractionation of an extract prepared from HeLa cells infected with vaccinia virus resulted in the separation of factors involved in vaccinia virus intermediate transcription. Two activities, VITF-A and VITF-B, in addition to the viral RNA polymerase are necessary and sufficient to direct intermediate transcription in vitro. VITF-B confers intermediate promoter specificity to an early-specific extract prepared from virus particles. A committed complex between VITF-B and the template can sequester VITF-A and RNA polymerase into a pre-initiation complex. VITF-B is further able to melt the promoter at the start site of transcription. Open complex formation is stimulated by ATP. In contrast to prokaryotic and eukaryotic pol III transcription, promoter melting is independent of the presence of RNA polymerase.
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PMID:Promoter melting by a stage-specific vaccinia virus transcription factor is independent of the presence of RNA polymerase. 201 91

The 35S rRNA gene of the yeast Saccharomyces cerevisiae was fused to the GAL7 promoter. This hybrid gene, when present on a multicopy plasmid and induced by galactose, suppressed the growth defects of a temperature-sensitive RNA polymerase I (pol I) mutant and those of a mutant in which the gene for the second largest subunit of pol I was deleted. Analysis of pulse-labeled RNA directly demonstrated that rRNA synthesis in this deletion mutant is from the GAL7 promoter. These experiments show that the sole essential function of pol I is the transcription of the rRNA genes, that pol I is not absolutely required for the synthesis of rRNA and ribosomes or cell growth if 35S rRNA synthesis is achieved by some other means, and that the tandemly repeated structure of the chromosomal rRNA genes is also not absolutely required for the synthesis of rRNA and ribosomes.
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PMID:Synthesis of large rRNAs by RNA polymerase II in mutants of Saccharomyces cerevisiae defective in RNA polymerase I. 202 44

The (+) single-stranded RNA (ssRNA) of the L-A virus is the species packaged to form new viral particles. Empty L-A viral particles specifically bind viral (+) ssRNA, and a sequence 400 bases from the 3' end is necessary for this activity. We show that its stem-loop structure, the A residue protruding from the stem, and the loop sequence are all important for the binding, and that this 34 base region is sufficient for the binding. M1, a satellite virus of L-A, has a similar structure on its (+) strand that is likewise sufficient for the binding. Heterologous RNA with the binding sequence from L-A or M1, when expressed in vivo, was packaged in L-A viral particles. Thus, the sites necessary to bind to empty particles are encapsidation signals for the L-A virus. Since the pol domain of the 180 kd minor coat protein appears to be responsible for the binding, this result suggests that the RNA polymerase molecule recognizes the viral genome for packaging.
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PMID:Portable encapsidation signal of the L-A double-stranded RNA virus of S. cerevisiae. 211 1

The 18-base-pair sequence element AGGTCGACCAGTACTCCG (the Sal box) signals termination of mouse ribosomal gene transcription. This sequence is recognized by a sequence-specific DNA-binding protein, TTF I, which mediates the termination of transcription by RNA polymerase I (pol I). Subsequently, the ends of the primary transcripts are trimmed by 10 nucleotides in a sequence-dependent 3'-terminal processing reaction. We have now investigated whether TTF I bound to its target sequence will block elongation by any RNA polymerase by steric hindrance, or whether it is specific for elongation by pol I. The results demonstrate that TTF I directs transcription termination with RNA polymerase I from species as divergent as mouse and yeast, but fails to affect elongation by heterologous polymerases (eukaryotic RNA polymerases II and III, Escherichia coli or bacteriophage T3 RNA polymerase). By contrast, purified lac repressor bound to its operator sequence stops elongation by both RNA polymerase I and II.
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PMID:Specific interaction of the murine transcription termination factor TTF I with class-I RNA polymerases. 218 20

The double-stranded RNA (dsRNA) viruses of Saccharomyces cerevisiae consist of 4.5-kilobase-pair (kb) L species and 1.7- to 2.1-kb M species, both found in cytoplasmic viruslike particles (VLPs). The L species encode their own capsid protein, and one (LA) has been shown to encode a putative capsid-polymerase fusion protein (cap-pol) that presumably provides VLPs with their transcriptase and replicase functions. The M1 and M2 dsRNAs encode the K1 and K2 toxins and specific immunity mechanisms. Maintenance of M1 and M2 is dependent on the presence of LA, which provides capsid and cap-pol for M dsRNA maintenance. Although a number of different S. cerevisiae killers have been described, only K1 and K2 have been studied in any detail. Their secreted polypeptide toxins disrupt cytoplasmic membrane functions in sensitive yeast cells. K28, named for the wine S. cerevisiae strain 28, appears to be unique; its toxin is unusually stable and disrupts DNA synthesis in sensitive cells. We have now demonstrated that 4.5-kb L28 and 2.1-kb M28 dsRNAs can be isolated from strain 28 in typical VLPs, that these VLPs are sufficient to confer K28 toxin and immunity phenotypes on transfected spheroplasts, and that the immunity of the transfectants is distinct from that of either M1 or M2. In vitro transcripts from the M28 VLPs show no cross-hybridization to denatured M1 or M2 dsRNAs, while L28 is an LA species competent for maintenance of M1. K28, encoded by M28, is thus the third unique killer system in S. cerevisiae to be clearly defined. It is now amenable to genetic analysis in standard laboratory strains.
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PMID:K28, a unique double-stranded RNA killer virus of Saccharomyces cerevisiae. 220 3

In HeLa cells, RNA polymerase III (pol III)-mediated transcription is severely inhibited by poliovirus infection. This inhibition is due primarily to the reduction in transcriptional activity of the pol III transcription factor TFIIIC in poliovirus-infected cells. However, the specific binding of TFIIIC to the VAI gene B-box sequence, as assayed by DNase I footprinting, is not altered by poliovirus infection. We have used gel retardation analysis to analyze TFIIIC-DNA complexes formed in nuclear extracts prepared from mock- and poliovirus-infected cells. In mock-infected cell extracts, two closely migrating TFIIIC-containing complexes, complexes I and II, were detected in the gel retardation assay. The slower migrating complex, complex I, was absent in poliovirus-infected cell extracts, and an increase occurred in the intensity of the faster-migrating complex (complex II). Also, in poliovirus-infected cell extracts, a new, rapidly migrating complex, complex III, was formed. Complex III may have been the result of limited proteolysis of complex I or II. These changes in TFIIIC-containing complexes in poliovirus-infected cell extracts correlated kinetically with the decrease in TFIIIC transcriptional activity. Complexes I, II, and III were chromatographically separated; only complex I was transcriptionally active and specifically restored pol III transcription when added to poliovirus-infected cell extracts. Acid phosphatase treatment partially converted complex I to complex II but did not affect the binding of complex II or III. Dephosphorylation and limited proteolysis of TFIIIC are discussed as possible mechanisms for the inhibition of pol III-mediated transcription by poliovirus.
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PMID:A transcriptionally active form of TFIIIC is modified in poliovirus-infected HeLa cells. 220 7

The role of various sequences in determining the RNA polymerase III (pol III) specificity of the Xenopus U6 gene promoter has been investigated. A sequence closely resembling an RNA polymerase II (pol II) TATA box, which has previously been implicated in determining the pol III specificity of the U6 promoter, was analyzed in detail. The U6 TATA-like element, in a different promoter context, is shown to be capable of mediating RNA polymerase II transcription both in vitro and in oocyte microinjection experiments. Extensive mutagenesis of the TATA-like element in the context of the pol III and pol II promoters leads to the conclusion that the sequence requirements for function in the two contexts are dissimilar, suggesting that different factors may be involved in mediating pol II and pol III transcription. Further, as implied by the above results, it is shown that the polymerase III specificity of the U6 gene is not solely dependent upon the TATA-like element but rather reflects complex interaction between multiple components of the promoter.
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PMID:Complex requirements for RNA polymerase III transcription of the Xenopus U6 promoter. 221 58

Vertebrate genes coding for U6 small nuclear RNA are transcribed by RNA polymerase III (pol III), using only upstream promoter elements rather than the A and B block internal control regions typical of most pol III transcription units. We show that expression of the U6 gene from the yeast Saccharomyces cerevisiae has two unexpected features: it requires a B block promoter element, and this element is located in a novel position, 120 bp downstream of the coding region. In tRNA genes, the B block is the primary binding site for transcription factor (TF) IIIC, whose function is to promote the subsequent binding of TFIIIB. Both factors are thus implicated in yeast U6 gene transcription. We present a model of the U6 transcription complex based on the structure of yeast and vertebrate U6 promoters.
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PMID:Transcription of a yeast U6 snRNA gene requires a polymerase III promoter element in a novel position. 222 12


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