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)

An Escherichia coli mutant lacking HSP70 function, delta dnaK52, is unable to grow at both high and low temperatures and, at intermediate temperature (30 degrees C), displays defects in major cellular processes such as cell division, chromosome segregation and regulation of heat shock gene expression that lead to poor growth and genetic instability of the cells. In an effort to understand the roles of molecular chaperones such as DnaK in cellular metabolism, we analyzed secondary mutations (sid) that suppress the growth defects of delta dnaK52 mutants at 30 degrees C and also permit growth at low temperature. Of the five suppressors we analyzed, four were of the sidB class and mapped within rpoH, which encodes the heat shock specific sigma subunit (sigma 32) of RNA polymerase. The sidB mutations affected four different regions of the sigma 32 protein and, in one case, resulted in a several fold reduction in the cellular concentration of sigma 32. Presence of any of the sidB mutations in delta dnaK52 mutants as well as in dnaK+ cells caused down-regulation of heat shock gene expression at 30 degrees C and decreased induction of the heat shock response after shift to 43.5 degrees C. These findings suggest that the physiologically most significant function of DnaK in the metabolism of unstressed cells is its function in heat shock gene regulation.
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PMID:Mutations altering heat shock specific subunit of RNA polymerase suppress major cellular defects of E. coli mutants lacking the DnaK chaperone. 224 63

When hybridization subtraction was used to enrich for sequences induced by heat shock in Chinese hamster cells, B2 sequences were found to be one of the major sequences enriched. With cloned B2 probes, we found that the level of the short, 0.1 to 0.6 kb, polyadenylated RNA polymerase III transcripts of this repetitive genetic element increased approximately 10 to 20 fold after heat shock. Transcription of B2 RNA by RNA polymerase III was rapidly induced after heat shock based on time course studies and nuclear runoff experiments. The induction of B2 RNA was not a nonspecific response to lethality or cellular injury because maximum B2 RNA induction was observed with even nontoxic heating while no induction occurred with other agents such as UV or X-radiation. Since B2 RNA increased after heat shock in several different Chinese hamster and mouse cell lines, induction of B2 RNA by heat shock is probably common in rodent cells. B2 RNA may also be the most abundant transcript induced by heat shock because the level of B2 RNA was substantially higher than several other abundant transcripts induced by heat shock including a rodent HSP70. Our finding of the induction of high levels of RNA polymerase III B2 transcripts in different rodent cells raise the possibility of a role in the heat shock response.
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PMID:Induction of B2 RNA polymerase III transcription by heat shock: enrichment for heat shock induced sequences in rodent cells by hybridization subtraction. 242 59

Mouse spermatogenic cells are known to express HSP70-2, a member of the HSP70 family of heat-shock proteins. The purpose of the present study was to characterize further the expression and localization of HSP70-2 in meiotic cells of mice and hamsters. After separating mouse spermatogenic cells into cytoplasmic and nuclear fractions, proteins were separated by two-dimensional gel electrophoresis and detected with HSP-specific antibodies. Of several HSP70 proteins identified in the cytoplasm, only HSC70 and HSP70-2 were also detected in the nucleus. Immunocytological analyses of spermatocyte prophase cells revealed that HSP70-2 was associated with the synaptonemal complex. Surface-spread synaptonemal complexes at pachytene and diplotene stages labeled distinctly with the antiserum to HSP70-2. Synaptonemal complexes from fetal mouse oocytes failed to show any evidence of HSP70-2. Reverse-transcriptase-polymerase chain reaction (RT-PCR) analyses of gene expression confirmed this sex specificity; Hsp70-2 mRNA was detected in mouse testes, but not ovaries. These findings are suggestive of a previously unsuspected sexual dimorphism in structure and/or function of the synaptonemal complex.
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PMID:HSP70-2 is part of the synaptonemal complex in mouse and hamster spermatocytes. 860 36

Polyomavirus large T-antigen transgenic mice develop cardiac hypertrophy characterized by an increase in atrial natriuretic factor and beta-myosin heavy chain isoform expression. The aim of this study was to examine changes in proto-oncogene expression in hypertrophied hearts from the transgenic mice. Expression of early growth response-1 (Egr-1) mRNA was detected in hearts from all 15 transgenic mice, but was not detectable in 13 control mice. Reverse transcriptase-polymerase chain reaction experiments using Egr-1-specific primers confirmed the increase in Egr-1 mRNA in enlarged hearts from the transgenic mice. Expression of c-jun, junD and Ha-ras mRNAs was increased in the transgenic hearts 3, 17 and 2.8-fold respectively. Western blots showed an increase in c-myc, c-jun and ras protein in hypertrophied transgenic hearts. Immunofluorescence analyses confirmed an increase in Egr-1 and c-jun protein in transgenic cardiomyocytes. Proliferating cell nuclear antigen, Ki-ras and HSP 90 mRNAs were decreased 22, 2.7 and 3-fold, respectively in the transgenic hearts. Not altered in most hypertrophied hearts was expression of c-fos, junB, p53, c-neu, c-myc, HSP70, HSP27, TGF-beta or IGF 1 mRNAs. Proto-oncogene and growth factor gene expression in hypertrophy induced by PVLT expression is modulated with some proto-oncogenes increased and others decreased in expression.
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PMID:Molecular remodelling in hypertrophied hearts from polyomavirus large T-antigen transgenic mice. 875 Nov 59

The heat shock response in Drosophila is primarily dependent on the binding of the heat shock transcription factor, HSF, to conserved sequences in heat shock gene promoters, the heat shock elements (HSEs). Here we examine the kinetic relationship of HSF binding to chromosomal loci and heat shock gene transcription in vivo. The features of heat shock promoters that determine the kinetics of HSF binding are also examined. Analyses of HSF association by indirect immunofluorescence with an anti-HSF antibody reveal that fluorescent signals at many loci on polytene chromosomes rapidly increase and then gradually decrease as heat shock time progresses. While overall amounts of fluorescent signal vary from locus to locus, the patterns of acquisition and loss of HSF at most loci are coordinated with only one identified exception. Immunostaining with an anti-RNA polymerase II antibody indicates that the kinetics of RNA polymerase II accumulation on the heat shock loci are similar to those of HSF. Furthermore, nuclear run-on assays confirm that the major heat shock genes are coordinately transcribed during the attenuation period. In contrast, the kinetics of HSF association with HSE "polymers" in a transgenic fly strain are not coordinated with those of endogenous loci. The addition of core promoter sequences to one of the HSEs found in the polymer restores coordinate HSF binding, suggesting that the kinetic patterns of HSF binding depend on a core promoter located near the HSEs. Finally, the distribution of the heat shock protein HSP70 is examined for its role in regulating the attenuated response of HSF to heat shock.
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PMID:HSF recruitment and loss at most Drosophila heat shock loci is coordinated and depends on proximal promoter sequences. 878 Nov 84

The capacity of preexisting antioxidant pathways to handle oxidative stress during exercise may be complemented by the synthesis of inducible heat stress proteins (HSP). Our purpose was to determine if the amount of mRNA for HSP32, a major oxidative stress protein, was increased in muscle after repetitive contractions. Reverse transcriptase-polymerase chain reaction analysis showed that HSP32 mRNA (normalized to alpha-actin mRNA) was increased about seven- and about fourfold (P < 0.35) immediately after 1 h of exhaustive running and after 3 h of muscle contractions (10 Hz nerve stimulation), respectively. Northern blot analysis revealed that HSP70 mRNAs were 3.5- to 15.5-fold above control value (P < 0.05), whereas the content of another oxidative stress protein mRNA (macrophage stress protein 23) was unchanged 0 h after contractions. The relative increase in HSP32 mRNA was found to be dependent on active tension generation; passive tension did not increase the HSP32-to-actin mRNA ratio. Increases in HSP32 mRNA may underlie an inducible antioxidant pathway in muscle responsive to metabolic stresses associated with repeated muscle contractions.
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PMID:Induction of heme oxygenase-1 (HSP32) mRNA in skeletal muscle following contractions. 903 11

A full-length cDNA clone of beet yellows closterovirus (BYV) was engineered and used to map functions involved in the replication of the viral RNA genome and subgenomic RNA formation. Among 10 open reading frames (ORFs) present in BYV, ORFs 1a and 1b suffice for RNA replication and transcription. The proteins encoded in these ORFs harbor putative methyltransferase, RNA helicase, and RNA polymerase domains common to Sindbis virus-like viruses and a large interdomain region that is unique to closteroviruses. The papain-like leader proteinase (L-Pro) encoded in the 5'-proximal region of ORF 1a was found to have a dual function in genome amplification. First, the autocatalytic cleavage between L-Pro and the remainder of the ORF 1a product was essential for replication of RNA. Second, an additional L-Pro function that was separable from proteolytic activity was required for efficient RNA accumulation. The deletion of a large, approximately 5.6-kb, 3'-terminal region coding for a 6-kDa hydrophobic protein, an HSP70 homolog, a 64-kDa protein, minor and major capsid proteins, a 20-kDa protein, and a 21-kDa protein (p21) resulted in replication-competent RNA. However, examination of mutants with replacements of start codons in each of these seven 3'-terminal ORFs revealed that p21 functions as an enhancer of genome amplification. The intriguing analogies between the genome organization and replicational requirements of plant closteroviruses and animal coronavirus-like viruses are discussed.
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PMID:Genes required for replication of the 15.5-kilobase RNA genome of a plant closterovirus. 962 Oct 48

Actinomycin D and alpha-amanitin are commonly used to inhibit transcription. Unexpectedly, however, the transcription of the human immunodeficiency virus (HIV-1) long terminal repeats (LTR) is shown to be activated at the level of elongation, in human and murine cells exposed to these drugs, whereas the Rous sarcoma virus LTR, the human cytomegalovirus immediate early gene (CMV), and the HSP70 promoters are repressed. Activation of the HIV LTR is independent of the NFkappaB and TAR sequences and coincides with an enhanced average phosphorylation of the C-terminal domain (CTD) from the largest subunit of RNA polymerase II. Both the HIV-1 LTR activation and the bulk CTD phosphorylation enhancement are prevented by several CTD kinase inhibitors, including 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole. The efficacies of the various compounds to block CTD phosphorylation and transcription in vivo correlate with their capacities to inhibit the CDK9/PITALRE kinase in vitro. Hence, the positive transcription elongation factor, P-TEFb, is likely to contribute to the average CTD phosphorylation in vivo and to the activation of the HIV-1 LTR induced by actinomycin D.
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PMID:The transcriptional inhibitors, actinomycin D and alpha-amanitin, activate the HIV-1 promoter and favor phosphorylation of the RNA polymerase II C-terminal domain. 1034 61

Resolving the order of events that occurred during the transition from prokaryotic to eukaryotic cells remains one of the greatest problems in cell evolution. One view, the Archezoa hypothesis, proposes that the endosymbiotic origin of mitochondria occurred relatively late in eukaryotic evolution and that several mitochondrion-lacking protist groups diverged before the establishment of the organelle. Phylogenies based on small subunit ribosomal RNA and several protein-coding genes supported this proposal, placing amitochondriate protists such as diplomonads, parabasalids, and Microsporidia as the earliest diverging eukaryotic lineages. However, trees of other molecules, such as tubulins, heat shock protein 70, TATA box-binding protein, and the largest subunit of RNA polymerase II, indicate that Microsporidia are not deeply branching eukaryotes but instead are close relatives of the Fungi. Furthermore, recent discoveries of mitochondrion-derived genes in the nuclear genomes of entamoebae, Microsporidia, parabasalids, and diplomonads suggest that these organisms likely descend from mitochondrion-bearing ancestors. Although several protist lineages formally remain as candidates for Archezoa, most evidence suggests that the mitochondrial endosymbiosis took place prior to the divergence of all extant eukaryotes. In addition, discoveries of proteobacterial-like nuclear genes coding for cytoplasmic proteins indicate that the mitochondrial symbiont may have contributed more to the eukaryotic lineage than previously thought. As genome sequence data from parabasalids and diplomonads accumulate, it is becoming clear that the last common ancestor of these protist taxa and other extant eukaryotic groups already possessed many of the complex features found in most eukaryotes but lacking in prokaryotes. However, our confidence in the deeply branching position of diplomonads and parabasalids among eukaryotes is weakened by conflicting phylogenies and potential sources of artifact. Our current picture of early eukaryotic evolution is in a state of flux.
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PMID:Reconstructing Early Events in Eukaryotic Evolution. 1052 24

The amphibian oocyte represents an excellent model for the study of transcription regulation. Indeed, any modification of transcriptional activity is directly reflected in lampbrush chromosome structure by concomitant morphological changes. Previous studies have led to the hypothesis of a putative role for heat-shock proteins HSP70 and/or HSC70 in transcriptional processes in the oocyte. In order to dissect out the relative role of HSP70 or HSC70 in these processes, we used an oligo-antisense strategy to specifically inhibit the function of the targeted protein. Effects of hsc70 and hsp70 antisense oligodeoxynucleotides were analyzed in terms of both mRNA quantity and protein synthesis. Their effects on oocyte transcription were analyzed at the level of structural organization of lampbrush chromosomes and nucleolar transcriptional activity. Our results show that specific inactivation of hsc70 mRNA by hsc70 antisense oligos led to a reversible inhibition of lampbrush chromosome transcription. However, such reversible inhibition of transcription is considered non-sequence specific since it is also induced by any oligo. In contrast, specific inactivation of hsp70 mRNA by hsp70 antisense oligos, which is correlated with a drop of HSP70 neosynthesis, results in an irreversible inhibition of lampbrush chromosome transcription. Furthermore, our results show that the inactivation of hsp70 or hsc70 mRNAs does not affect nucleolar transcription. Such data suggest a role for HSP70 in the control of chromatin modifications related to RNA polymerase II transcriptional activity.
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PMID:HSP70 is involved in the control of chromosomal transcription in the amphibian oocyte. 1103 17


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