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)

Heat shock leads to co-ordinate increases in transcription of a family of heat shock genes, including the mouse hsp70.1 and B2 genes. Activation of the heat shock transcription factor (HSF) by heat shock stimulates transcription of the murine hsp70.1 gene (by RNA polymerase II). B2 genes are short, repetitive sequences whose transcription (by RNA polymerase III) are also increased after heat shock. We have studied whether heat-induced transcription is auto-regulated by the products of the heat shock genes. The results indicate: (1) after an initial heat shock, transcription of the heat shock genes by RNA polymerases II and III becomes desensitized to further heat shock, and the heat-induced DNA binding activity of the HSF is lost, (2) if accumulation of heat shock gene products is inhibited, the desensitizing effect of a prior heat shock is removed, and (3) transcription of the hsp70.1 and B2 genes apparently involves different mechanisms, with hsp70.1 employing the HSF and the B2 gene using a separate, heat-activated transcriptional mechanism. However, the level of transcription from the hsp70.1 and B2 genes and the stability of their respective RNAs are co-ordinately regulated by the level of heat shock protein in the cell. The data indicate that auto-regulation of the level of mouse heat shock gene products is mediated by RNA polymerase II transcripts but that the regulatory mechanism can control transcription from RNA polymerase III genes as well.
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PMID:Heat-induced transcription from RNA polymerases II and III and HSF binding activity are co-ordinately regulated by the products of the heat shock genes. 138 51

In vivo UV cross-linking and nuclear transcriptional run-on experiments have shown that a number of Drosophila genes possess an elongationally paused RNA polymerase on their 5' ends. Here, we examine in vivo promoters that do and do not possess paused polymerases using the single-stranded DNA-probing reagent KMnO4. Melted DNA helices are found associated with the pause site of the uninduced hsp70 and hsp26 heat shock genes and the constitutively expressed beta-1 tubulin gene. The histone H1 and H2B genes, which lack a paused polymerase, have no comparable region of melted DNA. Melting at the pause site persists upon heat shock induction of the hsp70 and hsp26 genes, indicating that pausing continues after gene activation. Interestingly, activation triggers additional melting, both at the start site (in the region where open complexes would be expected to form) and downstream of the uninduced pause site. In the course of our studies, we discovered that some T residues of the TATA box were protected from KMnO4 modification in both induced and uninduced cells. This protection appears to be a consequence of TFIID binding, as a similar protection pattern could be produced in vitro with purified protein.
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PMID:Promoter melting and TFIID complexes on Drosophila genes in vivo. 142 79

Under conditions unfavorable to growth, the nematode Caenorhabditis elegans enters a developmentally arrested stage, the dauer larva. We have examined gene expression in the dauer larva and during recovery from the dauer stage. Run-on transcription assays with isolated nuclei reveal a depression of general RNA polymerase II transcription to 11-17% of that in other stages. Transcription of individual gene families (including actin, collagen, hsp70, and histone) is similarly depressed relative to actively growing stages. Dauer larvae are, however, capable of being induced for heat shock messages, indicating that they are competent to initiate and elongate transcripts. For most genes surveyed, reduced transcription in dauer larvae correlates with a decrease in message abundance. Hsp70 mRNA, however, is transcribed at lower rates but accumulates at levels comparable to those in other stages. Interestingly, dauer larvae are 15-fold enriched in a mRNA for a C. elegans hsp90 gene. Hsp90 mRNA accumulation is regulated at least in part by differential stability. Dauer larvae thus appear to have a unique pattern of gene expression. Upon placement in food, dauer larvae reenter the developmental pathway as late-stage larvae. Dauer recovery is accompanied by a temporally regulated sequence of gene expression. At least four distinct patterns of gene expression can be distinguished during exit from the dauer stage. Steady-state levels of hsp70 and polyubiquitin mRNA rise sharply within 75 min of recovery before declining by the fourth hour. Actin and histone mRNAs increase steadily following 2-4 hr of recovery, whereas myosin mRNA increases after 10 hr. In contrast, hsp90 mRNA declines sharply within the first 75 min of recovery. Changes in mRNA populations during dauer formation and exit may be physiologically relevant.
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PMID:Gene expression in the Caenorhabditis elegans dauer larva: developmental regulation of Hsp90 and other genes. 157 99

In vitro transcription was reconstituted with HeLa cell transcription factors and RNA polymerase II, which were essentially free from DNA topoisomerase activities. DNA templates with defined negative superhelical densities were tested for transcription activity. Transcription of the Bombyx mori fibroin gene increases and plateaus from templates of increasing superhelicity, and transcription from the adenovirus 2 major late promoter rises and then falls, while transcription of the Drosophila hsp70 gene remains unchanged. Dissection of transcription into pre and post-initiation steps by the use of Sarkosyl reveals that formation of a preinitiation complex on the fibroin gene or the adenovirus 2 major late promoter is slow on relaxed DNA and accelerated by DNA superhelicity. On the contrary, the preinitiation complex assembles rapidly on the hsp70 gene irrespective of DNA topology. As is the case with the fibroin gene promoter, DNA superhelicity appears to facilitate the interaction of transcription factor IID to the adenovirus 2 major late promoter.
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PMID:DNA superhelicity affects the formation of transcription preinitiation complex on eukaryotic genes differently. 164 22

RNA polymerase II is transcriptionally engaged but paused approximately 25 nucleotides from the start site of the hsp70 gene of Drosophila melanogaster in uninduced (non-heat-shocked) flies. Here, we identify regions of the hsp70 promoter that are required for formation of this paused polymerase. Various hsp70 promoter sequences are substituted for promoter sequences of a yolk protein gene, yp1, which, in males, is normally not expressed and has no paused polymerase. Run-on assays with nuclei of male transgenic flies are used to measure the level of paused polymerase on the hybrid genes. Sequences that reside upstream of the hsp70 TATA element, when fused upstream of the yp1 TATA element, specify the formation of a paused polymerase on the 5' end of this hybrid gene. Within this region are multiple copies of the GAGA element, which is known to bind a constitutively expressed factor. This element appears to play a role in generating the pause. Also, in the absence of much of this upstream region, hsp70 sequences in the vicinity of the transcriptional start and pause site participate in specifying the pause. Deletions of the pause site reduce the level of paused polymerase but do not lead to constitutive transcription. However, a connection between transcription and pausing is seen. The level of paused polymerase on the various hybrid hsp70-yp1 promoters correlates with the promoter's potential to direct heat-induced transcription.
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PMID:DNA sequence requirements for generating paused polymerase at the start of hsp70. 173 19

An RNA polymerase II molecule is associated with the 5' end of the Drosophila melanogaster hsp70 gene under non-heat shock conditions. This polymerase is engaged in transcription but has paused, or arrested, after synthesizing about 25 nucleotides (A. E. Rougvie and J. T. Lis, Cell 54:795-804, 1988). Resumption of elongation by this paused polymerase appears to be the rate-limiting step in hsp70 transcription in uninduced cells. Here we report results of nuclear run-on assays that measure the distribution of elongating and paused RNA polymerase molecules on the hsp70 gene in induced cells. Pausing of polymerase was detected at the 5' end of hsp70 in cells exposed to the intermediate heat shock temperatures of 27 and 30 degrees C. At 30 degrees C, each copy of hsp70 was transcribed approximately five times during the 25-min heat shock that we used. Therefore, once the hsp70 gene is induced to an intermediate level, initiation of transcription by RNA polymerase II remains more rapid than the resumption of elongation by a paused polymerase molecule.
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PMID:RNA polymerase II pauses at the 5' end of the transcriptionally induced Drosophila hsp70 gene. 192 45

The E1A region of the adenoviral genome, important for initiation of virus infection and activation of other viral genes, was chosen as a target for engineering antisense RNA (asRNA) to inhibit adenovirus 5 (Ad5) replication in COS-1 cell culture in vitro. The hsp70 promoter, taken from the appropriate heat-shock-protein gene of Drosophila melanogaster, and the VA-1 RNA promoter, derived from the Ad5 gene coding for low-molecular-mass VA-1 RNA and recognized by RNA polymerase III were used as regulatory elements of transcription. The two types of recombinant constructs contained E1A fragments of 710 bp (hsp70 constructs) or 380 or 740 bp (VA-1 RNA constructs) in reverse orientation relative to the promoter position, as well as a transcription termination signal, the SV40 ori, and the gene controlling Geneticin (antibiotic G418) resistance (G418R). After selection of transfected COS-1 cells in the presence of G418, a number of stable G418R cell lines were raised which expressed engineered asRNAs. Plating of Ad5 suspensions of known titre on monolayers of transfected COS-1 cells clearly showed strong inhibition of adenovirus replication by asRNAs: 75% with the hsp70 promoter and 90% with the VA-1 RNA promoter.
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PMID:Inhibition of adenovirus replication by the E1A antisense transcript initiated from hsp70 and VA-1 promoters. 215 50

Drosophila hsp70 genes have an RNA polymerase II molecule paused at their 5' ends in uninduced cells. In this study we have shown that this pausing also occurs on other heat shock and constitutively expressed genes. We propose that a rate-limiting step in early elongation occurs in many Drosophila genes and may be a target for transcriptional regulation.
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PMID:Postinitiation transcriptional control in Drosophila melanogaster. 217 90

Pelham previously proposed that the hsp70 family of heat shock proteins could prevent the formation and/or allow the dissolution of protein aggregates created during stress conditions. We confirmed this hypothesis by showing that the E. coli hsp70 homolog, the dnaK gene product, protects the host RNA polymerase enzyme from heat inactivation in an ATP-independent reaction. In addition, we show that heat-inactivated and aggregated RNA polymerase is both disaggregated and reactivated following simultaneous incubation with DnaK protein and hydrolyzable ATP. The DnaK756 mutant protein has lost the ability to disaggregate the inactivated RNA polymerase enzyme. Our results demonstrate that the DnaK protein contributes to E. coli's growth not only by protecting some enzymes from denaturation but also by reactivating some once they are misfolded or aggregated.
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PMID:The E. coli dnaK gene product, the hsp70 homolog, can reactivate heat-inactivated RNA polymerase in an ATP hydrolysis-dependent manner. 220 39

The induction of puff III-A3b, a major heat-shock puff in Chironomus thummi salivary cells, was insensitive to the transcription inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), whereas no transcriptional activity could be detected at the other heat-shock puffs in the presence of this drug. In these conditions, a polypeptide with the same Mr and isoform pattern as those of the major heat-shock polypeptide, hsp70, was synthesized. These results suggest that hsp70 is encoded by locus III-A3b. In addition to DRB insensitivity, incorporation of [3H]UTP on puff III-A3b took place in an in vitro transcription assay under low-salt conditions (100 mM NaCl); no labelling could be detected at the other heat-shock puffs under these conditions. Although DRB has been reported as a specific inhibitor of RNA polymerase II-directed transcription, and although the low-salt conditions were not propitious for the activity of this enzyme, RNA polymerase II was detected on puff III-A3b and on the other heat-shock puffs by immunofluorescence with anti-RNA polymerase II antibodies.
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PMID:Correlation between the activity of a 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-insensitive puff and the synthesis of major heat-shock polypeptide, hsp70, in Chironomus thummi. 246 51


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