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)

Levels of mRNA and protein encoded by the TATA-binding protein (tbp) gene are shown to increase dramatically during late spermatogenesis in rodents, culminating in a highly testis-enriched expression pattern. Whereas adult spleen and liver contained roughly 0.7 and 2.3 molecules of TBP mRNA per haploid genome-equivalent, respectively, adult testis contained 80-200 molecules of TBP mRNA per haploid genome-equivalent. Comparison of nuclear and cytoplasmic levels of TBP mRNA in liver and testis suggested that nuclear events (transcription or processing) contribute roughly 12-fold, and cytoplasmic events (mRNA stability) roughly 6-fold, to testis-specific overaccumulation. Levels of nuclear TBP protein in testis cells were, on average, 8- and 11-fold higher than those in liver and spleen cells, respectively. Overexpression of TBP mRNA in testis began about 20 days after birth and reached a plateau around day 40, corresponding to the developmental emergence of haploid cells. Besides TBP, two other components of the general RNA polymerase II machinery, TFIIB and RNA polymerase II, were also overexpressed in testis. By immunostaining, it was found that TBP and RNA polymerase II were particularly rich in round spermatid nuclei. Our results suggest a molecular explanation for how early spermatids are able to accumulate all of the mRNA necessary for the final week of spermiogenesis.
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PMID:High accumulation of components of the RNA polymerase II transcription machinery in rodent spermatids. 767 3

Transcription initiation from eukaryotic protein-coding genes is a complex process that minimally requires RNA polymerase (pol) II (B) and at least seven general transcription factors. The 38-kDa subunit (TBP) of the human general transcription factor TFIID recognizes the TATA sequence element and initiates the assembly of the other general transcription factors and RNA pol II. It is believed, based on experiments with yeast recombinant protein, that TBP binds as a monomer to DNA. Using purified recombinant human TBP protein we find that TBP interacts with the TATA element as both a monomer and a dimer. The multimeric binding of TBP to DNA revealed by this study has important implications for the role of TBP in transcription initiation and suggests novel mechanisms whereby other transcription factors may interact with a RNA pol II preinitiation complex.
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PMID:The DNA-binding subunit of human transcription factor IID can interact with the TATA box as a multimer. 834 93

The TATA-binding protein (TBP) is an essential component of the transcriptional machinery of all three nuclear RNA polymerase enzymes. Comparison of the amino acid sequence of TBPs from a number of species reveals a highly conserved 180-residue C-terminal domain. In contrast, the N terminus is variable in both size and amino acid sequence. Overexpression of a TBP protein with a deletion of the nonconserved N terminus (TBP delta 57) in Saccharomyces cerevisiae results in a dominant negative phenotype of extremely slow growth. Associated with the slow-growth phenotype are defects in RNA polymerase II transcription in vivo. We have screened a high-copy-number yeast genomic library for suppression of the slow-growth phenotype and have isolated plasmids which encode suppressors of TBP delta 57 overexpression. Here we report the sequence and initial characterization of one suppressor, designated STD1 for suppressor of TBP deletion. The STD1 gene contains a single continuous open reading frame with the potential to encode a 50.2-kDa protein. Disruption of the STD1 gene indicates that it is not essential for vegetative growth, mating, or sporulation. High-copy-number suppression by the STD1 gene is not the result of a decrease in TBP delta 57 protein accumulation or DNA-binding activity; instead, STD1 suppression is coincident with the elimination of TBP delta 57-induced RNA polymerase II defects in both uninduced and induced transcription in vivo.
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PMID:Isolation of STD1, a high-copy-number suppressor of a dominant negative mutation in the yeast TATA-binding protein. 849 75

We have investigated the role of the TATA-binding protein (TBP) in modulating RNA polymerase (Pol) III gene activity. Epitope-tagged TBP (e-TBP) was both transiently and stably transfected in Drosophila Schneider S-2 cells to increase the total cellular level of TBP. Analysis of the transcripts synthesized from cotransfected tRNA and U6 RNA genes revealed that both types of RNA Pol III promoters were substantially stimulated by an increase in e-TBP in a dose-dependent manner. Furthermore, a TBP-dependent increase in the levels of endogenous tRNA transcripts was produced in the stable line induced to express the e-TBP. We further determined whether the ability of increased TBP to induce RNA Pol III gene expression was due to a direct effect of increased TBP complexes on RNA Pol III gene promoters or an indirect consequence of enhanced expression of RNA Pol II genes. A TBP expression plasmid (e-TBP332), containing a mutation within the highly conserved carboxy-terminal domain, was both transiently and stably transfected into S-2 cells. e-TBP332 augmented the transcription from two RNA Pol II gene promoters indistinguishably from that observed when e-TBP was expressed. In contrast, e-TBP332 was completely defective in its ability to stimulate either the tRNA or U6 RNA gene promoters. In addition, increasing levels of a truncated TBP protein containing only the carboxy-terminal region failed to induce either the tRNA or U6 RNA gene promoter, whereas it retained its ability to stimulate an RNA Pol II promoter. Thus, the TBP-dependent increase in RNA Pol II gene activity is not sufficient for enhanced RNA Pol III gene transcription; rather, a direct effect on RNA Pol III promoters is required. Furthermore, these results provide the first direct evidence that the amino-terminal region of TBP is important for the formation or function of TBP-containing complexes utilized by TATA-less and TATA-containing RNA Pol III promoters. Together, these studies demonstrate that TBP is limiting for the expression of both classes of RNA Pol III promoters in Drosophila cells and implicate an important role for TBP in regulating RNA Pol III gene expression.
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PMID:TATA-binding protein is limiting for both TATA-containing and TATA-lacking RNA polymerase III promoters in Drosophila cells. 894 46

A subunit of the Drosophila RNA polymerase III transcription factor IIIB (TFIIIB) complex has been identified using antibodies directed against the analogous human protein, hIIIB90. This protein has an apparent molecular mass of 105 kDa and has been designated dTAFIII105. Drosophila S-2 cell extracts that were immunodepleted of dTAFIII105 were substantially reduced in their capacity to support tRNA gene transcription. A protein (far Western) blot analysis revealed that dTAFIII105, present in a TFIIIB fraction, directly interacts with TATA-binding protein (TBP). Coimmunoprecipitation assays demonstrated that this protein associates with TBP in S-2 cell extracts. Our previous studies have identified a mutation at position 332 within Drosophila TBP that changes a highly conserved arginine residue to a histidine residue, which renders it specifically defective in its ability to support RNA polymerase III transcription in S-2 cells (Trivedi, A., Vilalta, A., Gopalan, S., and Johnson, D. L. (1996) Mol. Cell. Biol. 16, 6909-6916). We further demonstrate that extracts prepared from a stable cell line expressing epitope-tagged wild-type TBP exhibit an increase in tRNA gene transcription, whereas extracts derived from cells expressing the mutant TBP protein do not. Coimmunoprecipitation assays and far Western blot analysis demonstrate that this mutation in TBP abolishes its ability to stably interact with dTAFIII105. Thus, we have identified both a Drosophila protein that is directly associated with TBP in the TFIIIB complex, dTAFIII105, and an amino acid residue within the highly conserved carboxyl-terminal region of TBP that is critical for dTAFIII105-TBP interactions.
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PMID:An RNA polymerase III-defective mutation in TATA-binding protein disrupts its interaction with a transcription factor IIIB subunit in drosophila cells. 921 40

The hepatitis B virus (HBV) X protein is essential for viral infectivity, and evidence indicates that it is a strong contributor to HBV-mediated oncogenesis. X has been shown to transactivate a wide variety of RNA polymerase (Pol) II-dependent, as well as RNA Pol III-dependent, promoters. In this study, we have investigated the possibility that X modulates RNA Pol I-dependent rRNA transcription. In both human hepatoma Huh7 and Drosophila Schneider S2 cell lines, X expression stimulated rRNA promoter activity. Extracts prepared from X-expressing cells stably transfected with an X gene also exhibited an increased ability to transcribe the rRNA promoter. The mechanism for X transactivation was examined by determining whether this regulatory event was dependent on Ras activation and increased TATA-binding protein (TBP) levels. Our previous studies have demonstrated that X, and the activation of Ras, produces an increase in the cellular levels of TBP (H.-D. Wang, A. Trivedi, and D. L. Johnson, Mol. Cell. Biol. 17:6838-6846, 1997). Expression of a dominant negative form of Ras blocked the X-mediated induction of the rRNA promoters, whereas expression of a constitutively activated form of Ras mimicked the enhancing effect of X on rRNA promoter activity. When TBP was overexpressed in either Huh7 or S2 cells, a dose-dependent increase in rRNA promoter activity was observed. To analyze whether the increase in TBP was modulating rRNA promoter activity indirectly, by increasing activity of RNA Pol II-dependent promoters, a Drosophila TBP cDNA was constructed with a mutation that eliminated its ability to stimulate RNA Pol II-dependent promoters. Transient expression of wild-type TBP in S2 cells increased the activities of specific RNA Pol I- and Pol II-dependent promoters. Expression of the mutant TBP protein failed to enhance the activity of the RNA Pol II-dependent promoters, yet the protein completely retained its ability to stimulate the rRNA promoter. Furthermore, the addition of recombinant TBP to S2 extracts stimulated rRNA promoter activity in vitro. Together, these results demonstrate that the HBV X protein up-regulates RNA Pol I-dependent promoters via a Ras-activated pathway in two distinct cell lines. The enhanced promoter activity can, at least in part, be attributed to the X- and Ras-mediated increase in cellular TBP, a limiting transcription component.
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PMID:Regulation of RNA polymerase I-dependent promoters by the hepatitis B virus X protein via activated Ras and TATA-binding protein. 981 95

During the infection cycle of Autographa californica multicapsid nuclear polyhedrosis virus, the TATA-binding protein (TBP) of the insect host cell likely participates in early viral transcription, which is mediated by the host RNA polymerase II. However, the role of TBP in late and very late viral transcription, which is accomplished by an alpha-amanitin-resistant RNA polymerase, is unclear. We observed a dramatic increase of TBP protein during the late phases of infection. TBP mRNA levels, however, were not coordinately increased. Indirect-immunofluorescence studies revealed a nuclear redistribution of TBP during infection. After labeling of viral replication centers with bromodeoxyuridine (BrdU), costaining of TBP and BrdU showed that TBP localized to viral DNA replication centers. These results suggest a putative role of TBP during late viral transcription, which may occur in close proximity to viral DNA replication.
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PMID:Baculovirus infection raises the level of TATA-binding protein that colocalizes with viral DNA replication sites. 1236 54

TATA binding protein (TBP) is a key regulator of RNA polymerase transcription. It binds to core promoters, often in large multiprotein complexes, and nucleates RNA polymerase II (Pol II) transcription initiation. In addition to the previously described TBP-like factor present in metazoans (TLF/TRF2/TRP/TLP), we describe a third, vertebrate-specific member of the TBP protein family from zebrafish, called TBP2. Evolutionary conserved TBP2 homologs were also found in human, mouse, frog, and pufferfish. The N-terminal domains of TBP2s are divergent amongst themselves and different from those of TBPs; however, the core domain of TBP2s and TBPs are almost identical. TBP2 binds the TATA box, interacts with TFIIA and TFIIB (similarly to TBP), and can mediate Pol II transcription initiation. However, TBP2 shows contrasting expression patterns in the gonads and during embryonic development in comparison to TBP, suggesting differential function. Knockdown of zebrafish TBP2 results in specific reduction of the protein level, leading to a phenotype, which indicates the requirement of TBP2 for embryonic patterning. The presence of three different TBP family members in vertebrates suggests the existence of developmental stage- and tissue-specific preinitiation complexes with specific requirements for different TBP family members.
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PMID:TBP2, a vertebrate-specific member of the TBP family, is required in embryonic development of zebrafish. 1506

The TATA-box-binding protein (TBP) plays a key role in initiating eukaryotic transcription and is used by many viruses for viral transcription. We previously reported increased TBP levels during infection with the baculovirus Autographa californica multicapsid nuclear polyhedrovirus (AcMNPV). The TBP antiserum used in that study, however, cross-reacted with a baculoviral protein. Here, we reported that increased amounts of nuclear TBP were detected upon infection of Spodoptera frugiperda and TN-368 cells with a TBP-specific antiserum. TBP levels increased until 72 h post-infection (p.i.), whilst tbp transcripts decreased by 16 h p.i., which suggested a virus-induced influence on the TBP protein levels. To address a potential modification of the TBP degradation pathway during infection, we investigated the possible role of viral ubiquitin. Infection studies with AcMNPV recombinants carrying a mutated viral ubiquitin gene revealed that the TBP increase during infection was not altered. In addition, pulse-chase experiments indicated a high TBP half-life of ~60 h in uninfected cells, suggesting that a virus-induced increase of TBP stability was unlikely. This increase in TBP correlated with a redistribution to nuclear domains resembling sites of viral DNA synthesis. Furthermore, we observed colocalization of TBP with host RNA polymerase (RNAP) II, but only until 8 h p.i., whilst TBP, but not RNAPII, was present in the enlarged replication domains late during infection. Thus, we suggested that AcMNPV adapted a mechanism to accumulate the highly stable cellular TBP at sites of viral DNA replication and transcription.
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PMID:Expression and nuclear localization of the TATA-box-binding protein during baculovirus infection. 2467 20

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