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 general transcription factor TFIIIC is necessary for transcription initiation by RNA polymerase III. TFIIIC binds predominantly to the B-Block promoter element, which is present in tRNA genes, several viral RNA genes and repetitive DNA elements, and to the TFIIIA.DNA complex on 5 S RNA genes. Here we report a characterization of Xenopus laevis TFIIIC and its interaction with the TFIIIA.5 S RNA gene complex. A polypeptide with apparent molecular mass of 85 kDa was specifically cross-linked to a B-Block oligonucleotide by UV light. This polypeptide was present in the partially purified TFIIIC fraction and in a complex with a B-Block double-stranded oligonucleotide isolated by nondenaturing gel electrophoresis. TFIIIC.TFIIIA.DNA gel mobility shift complexes were obtained using B-Block DNA affinity-purified TFIIIC and buffer conditions employing low Mg2+ (1 mM) and high dithiothreitol (7 mM) concentrations. Three TFIIIC.TFIIIA.5 S RNA gene complexes were observed by gel mobility shift analysis. One of these complexes was resistant to dissociation by the addition of competing DNA, but the formation of all three complexes was prevented by the inclusion of excess specific competitor DNA in the initial binding reactions. The apparent affinity of TFIIIC for the TFIIIA.5 S DNA complex was 5-fold higher for the somatic-type 5 S RNA gene than for the oocyte-type 5 S RNA gene. Mutations near the 5' boundary of the TFIIIA binding site alter the DNase I footprint of the TFIIIA.DNA complex and reduce the affinity of TFIIIA-mutant 5 S gene complexes for TFIIIC. Differences in TFIIIC affinity for the two classes of 5 S RNA genes may play a role in the developmental regulation of these gene families.
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PMID:Interaction of Xenopus TFIIIC with the TFIIIA.5 S RNA gene complex. 151 47

It is generally assumed that the machinery that transcribes genes is composed entirely of polypeptides. However, in vitro transcription by silkworm RNA polymerase III requires a transcription factor that is not a polypeptide. This component, TFIIIR, is distinct from the previously identified transcription components: RNA polymerase III, and the accessory factors TFIIIA, TFIIIB, TFIIIC, and TFIIID. The newly discovered TFIIIR is a macromolecule that appears to be composed of RNA. It is resistant to heat, detergent, phenol, protease, and deoxyribonuclease, but it is sensitive to alkali and ribonuclease.
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PMID:A class III transcription factor composed of RNA. 170 25

TFIIIA is an RNA polymerase III transcription factor that binds to the internal control region of the 5 S RNA gene as the first step in the assembly of a transcription complex. We have identified the gene encoding TFIIIA from Saccharomyces cerevisiae. Protein synthesized in vitro from the cloned gene has the same size, DNA-binding properties, and transcription factor activity as does purified yeast TFIIIA. Examination of the deduced sequence of the 50-kDa yeast transcription factor revealed the presence of nine zinc-finger motifs, a characteristic of Xenopus TFIIIA. Although the conservation of these nine putative DNA-binding domains is striking, the amino acid sequence throughout the corresponding fingers of the yeast and amphibian TFIIIAs has diverged extensively and in many instances the spacing between the residues that coordinate the zinc ions differs between the two proteins. A unique feature of the yeast protein is an 81-amino acid domain interrupting the repeated zinc-finger motifs between fingers 8 and 9. Additionally, the yeast and amphibian proteins differ in both the size and sequence of the amino- and carboxyl-terminal domains flanking the zinc fingers. The gene encoding yeast TFIIIA is present in single copy in the S. cerevisiae genome and is essential for cell viability. A carboxyl-terminal truncated form of the protein containing 4.5 zinc-finger motifs retains the ability to bind to DNA but is no longer active in promoting transcription in vitro.
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PMID:The deduced sequence of the transcription factor TFIIIA from Saccharomyces cerevisiae reveals extensive divergence from Xenopus TFIIIA. 173 84

The rapid induction of thionein (apometallothionein) by many endogenous stimuli such as steroid hormones, cytokines, and second messengers suggests that this cysteine-rich, metal binding protein participates in an as yet undefined role in cellular regulatory processes. This study demonstrates with DNA and RNA binding assays and in vitro transcription measurements that thionein suppresses the binding of the Xenopus laevis zinc finger transcription factor IIIA (TFIIIA) to 5S RNA and to the 5S RNA gene and abrogates the capacity of TFIIIA to initiate the RNA polymerase III-catalyzed synthesis of 5S RNA. The effect is reversed by the addition of zinc and is not observed in the TFIIIA-independent transcription of a tRNA gene by the same RNA polymerase. In view of the strong tendency of thionein to complex posttransition metals such as zinc, one effect of its enhanced synthesis in vivo could be to reduce the intracellular disposability of zinc and thus modulate the actions of zinc-dependent enzymes and proteins, most notably those of the zinc finger transcription factors.
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PMID:Zinc transfer from transcription factor IIIA fingers to thionein clusters. 183 92

The successful use of mixed heterologous in vitro transcription systems has suggested that the species specificity of RNA polymerase III transcription is low. To see if this extends to lower eukaryotic class III transcription factors, we compared the interactions of the two yeast assembly factors, TFIIIA and TFIIIC/tau factor, with a homologous yeast 5S rRNA gene and a heterologous Xenopus laevis somatic 5S rRNA gene. Transcription assays showed that the Xenopus gene was transcriptionally inactive in a crude cell-free yeast extract that actively transcribes the homologous gene. However, the Xenopus gene was still able to compete for limiting transcription factors. Electrophoretic DNA binding assays revealed that while TFIIIA bound avidly to the yeast gene (generating the 'A-complex'), it had no affinity for the Xenopus 5S rRNA gene. Nevertheless, a complex of both TFIIIA and TFIIIC/tau factor (the 'AC-complex') was formed on the two genes with similar affinity, although only the complex assembled on the homologous gene was able to activate transcription. Thus enough sequence information is present on the heterologous gene to direct transcription factor assembly, but not to activate transcription. Like its counterpart in Xenopus, the yeast TFIIIA appears to be a zinc binding protein that is inactivated by EDTA and 1,10-phenanthroline, and reactivated in the presence of zinc ions. Bound to the 5S rRNA gene, TFIIIA is however significantly more resistant to inactivation by chelators than in its free state. The AC-complex differs from the A-complex by being less affected by chelators, and by being more sensitive to the dissociating effect of single-stranded DNA.
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PMID:Yeast TFIIIA + TFIIIC/tau-factor, but not yeast TFIIIA alone, interacts with the Xenopus 5S rRNA gene. 201 29

Transcription factors IIIC (TFIIIC), TFIIIB and RNA polymerase III are commonly required for class III gene transcription in vitro. To understand the diversity and specificity of Xenopus TFIIIC, we have further characterized this factor. Our analyses indicate that a partially purified TFIIIC fraction contains an activity which specifically recognizes the "B" block element of TFIIIA gene. Stable complex formation assays with HeLa cell extracts demonstrate that the TFIIIA gene can stably sequester TFIIIC. off
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PMID:Xenopus transcription factor IIIC (TFIIIC) specifically interacts with the "B" block region of the TFIIIA gene. 202 35

In the absence of other components of the RNA polymerase III transcription machinery, transcription factor IIIA (TFIIIA) can be displaced from both strands of its DNA-binding site (the internal control region) on the somatic-type 5S rRNA gene of Xenopus borealis during transcription elongation by bacteriophage T7 RNA polymerase, regardless of which DNA strand is transcribed. Furthermore, substantial displacement is observed after the template has been transcribed only once. Since the complete 5S rRNA transcription complex has previously been shown to remain stably bound to the gene during repeated rounds of transcription by either RNA polymerase III or bacteriophage SP6 RNA polymerase, these results indicate that a factor(s) in addition to TFIIIA is required to create a complex that will remain stably associated with the template during transcription. Thus, transcription complex stability during passage of RNA polymerase cannot be explained solely on the basis of the DNA-binding properties of TFIIIA.
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PMID:Displacement of Xenopus transcription factor IIIA from a 5S rRNA gene by a transcribing RNA polymerase. 207 3

The Saccharomyces cerevisiae 5S rRNA gene was used as a model system to study the requirements for assembling transcriptionally active chromatin in vitro with purified components. When a plasmid containing yeast 5S rDNA was assembled into chromatin with purified core histones, the gene was inaccessible to the yeast class III gene transcription machinery. Preformation of a 5S rRNA gene-TFIIIA complex was not sufficient for the formation of active chromatin in this in vitro system. Instead, a complete transcription factor complex consisting of TFIIIA, TFIIIB, and TFIIIC needed to be formed before the addition of histones in order for the 5S chromatin to subsequently be transcribed by RNA polymerase III. Various 5S rRNA maxigenes were constructed and used for chromatin assembly studies. In vitro transcription from these assembled 5S maxigenes revealed that RNA polymerase III was readily able to transcribe through one, two, or four nucleosomes. However, we found that RNA polymerase III was not able to efficiently transcribe a chromatin template containing a more extended array of nucleosomes. In vivo expression experiments indicated that all in vitro-constructed maxigenes were transcriptionally competent. Analyses of protein-DNA interactions formed on these maxigenes in vivo by indirect end labeling indicated that there are extensive interactions throughout the length of these maxigenes. The patterns of protein-DNA interactions formed on these genes are consistent with these DNAs being assembled into extensive nucleosomal arrays.
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PMID:Transcription factor requirements for in vitro formation of transcriptionally competent 5S rRNA gene chromatin. 218 33

The major promoter element of the Xenopus laevis 5S RNA gene is located within the transcribed region of the gene and forms the binding site for the transcription initiation factor TFIIIA. We report an analysis of deletion and substitution mutations within the coding region of the major oocyte-type 5S gene of X. laevis. Our results differ from those of previous mutagenesis studies conducted on the somatic-type genes of Xenopus borealis and X. laevis. Transcription assays in whole oocyte S-150 extracts, with both oocyte- and somatic-type mutants, revealed additional promoter elements between the start site for transcription and the binding site for TFIIIA. These sequences regulate the efficiency of binding TFIIIC, a transcription factor required by the genes transcribed by RNA polymerase III containing intragenic promoters. Under TFIIIC-limiting conditions, the somatic-type gene had a 10-fold-higher affinity for TFIIIC than did the major oocyte-type 5S gene. One mutation in the oocyte-type gene (nucleotides +33 to +39) reduced TFIIIC affinity and transcriptional activity four- to fivefold. Differences in TFIIIC affinity between oocyte- and somatic-type genes may contribute to the differential transcription of these genes observed during Xenopus embryogenesis.
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PMID:Additional intragenic promoter elements of the Xenopus 5S RNA genes upstream from the TFIIIA-binding site. 239 87

Unlike the majority of genes encoding small nuclear RNAs, which are transcribed by RNA polymerase B, the U6 gene contains features found in both class B and class C genes, indicating the involvement of a combination of transcription factors normally specific to each class of genes. We present direct genetic and biochemical evidence that the U6 gene of Saccharomyces cerevisiae is transcribed by RNA polymerase C in vivo as well as in vitro. A mutant strain with a temperature-sensitive defect in the large subunit of RNA polymerase C that results in defective transcription of tRNA and 5S RNA genes shows a corresponding defect in U6 RNA levels. Also, purified RNA polymerase C transcribes the U6 gene when supplemented with partially purified TFIIIB. The other class C transcription factors, TFIIIA and Tau (TFIIIC), are not required in this system.
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PMID:The U6 gene of Saccharomyces cerevisiae is transcribed by RNA polymerase C (III) in vivo and in vitro. 240 27


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