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)

1. In order to demonstrate that triiodothyronine affects mitochondrial RNA synthesis by acting on the enzyme component of the DNA. RNA polymerase complex, mitochondrial RNA polymerase from thyroidectomized and hormone-treated rats was purified up to a stage in which activity was dependent on the addition of exogenous template. In these conditions and using different DNAs as templates, the enzyme from hormone-treated animals displayed an activity about double that of the activity of thyroidectomized animals. 2. Measurements of stability of mitochondrial RNA synthesized in vitro suggest, however, that the hormone can act also at the template level in mitochondrial transcription: the RNA population synthesized in vitro from hormone-treated rats is indeed much more enriched in unstable, probably messenger, RNA species. 3. The turnover of mitochondrial messenger RNA is higher after hormone treatment. 4. Adenosine cyclic 3':5'-monophosphate (cAMP) and its dibutyryl derivative added in vitro to mitochondria from thyroidectomized animals do not affect the incorporation of labeled precursor into mitochondrial RNA, suggesting that the level of the cyclic nucleotide in mitochondria is probably not involved in the hormone action. 5. It is concluded from these and previous studies that the thyroid hormone affects more than one parameter in the mitochondrial transcription process. The interrelationship between these events at molecular level remains, however, to be clarified.
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PMID:Effects of triiodothyronine on rat-liver mitochondrial transcription process. 16 68

The optimum conditions for transcription in vitro of yeast mtDNA into biologically relevant RNA by Escherichia coli RNA polymerase holoenzyme and yeast mitochondrial RNA polymerase was found to critically depend on salt concentration. RNA was transcribed (at 0.25 M KCl concentration) from high-molecular-weight mtDNA which was then translated in an E. coli (S-30) cell-free protein synthesising system. Efficient translation of mitochondrial RNA was achieved using conditions which had also been determined to be optimal in other systems. Identification of the polypeptides produced in the translation system was made using antiserum raised against mitochondrial membranes. Electrophoresis of the completely dissociated antigen-antibody complexes using dodecylsulphate-polyacrylamide gels revealed that the system in vitro produced polypeptides of similar molecular weight to those synthesised in vivo by cycloheximide-inhibited whole cells.
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PMID:Synthesis of mitochondrial proteins in an Escherichia coli cell-free system directed by yeast mitochondrial DNA. 80 75

We have purified the protein that confers selective promoter recognition on the core subunit of the yeast mitochondrial RNA polymerase. The N-terminal sequence of the 43-kDa specificity factor identified it as the product of the MTF1 gene described by Lisowsky and Michaelis (1988). We confirmed that MTF1 encoded the specificity factor by analyzing extracts from a yeast strain bearing a disruption of the gene. The extracts contained normal levels of core RNA polymerase but lacked selective transcription activity; adding the purified 43-kDa protein restored selective transcription. Comparison of the MTF1 protein sequence to the family of bacterial sigma factors has revealed striking similarity to domains identified with--10 promoter recognition, promoter melting, and holoenzyme stability.
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PMID:The yeast mitochondrial RNA polymerase specificity factor, MTF1, is similar to bacterial sigma factors. 193 77

Infection of Vero cells with herpes simplex virus type 1 results in the appearance in soluble extracts of a DNA primase activity. The partially purified enzyme, Mr, approximately 100,000, is identical in resistance to alpha-amanitin, pH profile, Mg2+ dependence, salt sensitivity, and KmATP to the catalytic core of Vero cell mitochondrial RNA polymerase. Moreover, the products synthesized are those expected of an RNA polymerase rather than a DNA primase. Inasmuch as the enzyme is not present in soluble extracts of uninfected Vero cells, we presume that the specific appearance of RNA polymerase in extracts of herpesvirus-infected cells results from infection-induced disruption of the mitochondrial membrane, followed by release of the enzyme into the cytosol.
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PMID:Release of RNA polymerase from vero cell mitochondria after herpes simplex virus type 1 infection. 215 32

A subset of promoters in the mitochondrial DNA (mtDNA) of the yeast Saccharomyces cerevisiae has been proposed to participate in replication initiation, giving rise to a primer through site-specific cleavage of an RNA transcript. To test whether transcription is essential for mtDNA maintenance, we examined two simple mtDNA deletion ([rho-]) genomes in yeast cells. One genome (HS3324) contains a consensus promoter (ATATAAGTA) for the mitochondrial RNA polymerase encoded by the nuclear gene RPO41, and the other genome (4a) does not. As anticipated, in RPO41 cells transcripts from the HS3324 genome were more abundant than were transcripts from the 4a genome. When the RPO41 gene was disrupted, both [rho-] genomes were efficiently maintained. The level of transcripts from HS3324 mtDNA was decreased greater than 400-fold in cells carrying the RPO41 disrupted gene; however, the low-level transcripts from 4a mtDNA were undiminished. These results indicate that replication of [rho-] genomes can be initiated in the absence of wild-type levels of the RPO41-encoded RNA polymerase.
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PMID:RPO41-independent maintenance of [rho-] mitochondrial DNA in Saccharomyces cerevisiae. 215 61

Specific transcription of yeast 35 S rDNA by RNA polymerase I has been demonstrated using fractionated extracts prepared from whole cells of Saccharomyces cerevisiae. Determination of the 5'-nucleotides of the in vitro transcripts indicated that two apparent start sites, corresponding to the first (initiating) and fifth nucleotide of the in vivo transcript, were utilized. Production of the 35 S rDNA transcript in this system was not inhibited by alpha-amanitin. Specific transcription of both the 35 S and 5 S rDNA sequences contained on the same template occurred simultaneously in these extracts. Sequential template competition experiments demonstrated that 35 S and 5 S rDNA transcription required different transcription factors. Specific antisera raised against the largest subunit of RNA polymerase I significantly inhibited synthesis of the 35 S rDNA transcript, but had a negligible effect on 5 S rRNA synthesis by RNA polymerase III. Additionally, this 35 S rDNA transcriptional activity was present in extracts prepared from a strain deficient in the mitochondrial RNA polymerase. Experiments using truncated rDNA templates showed that in vitro no more than 206 base pairs of the sequence upstream of the initiation site are required for maximal activity in this system; the enhancer element did not stimulate 35 S rDNA transcription.
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PMID:Specific transcription of Saccharomyces cerevisiae 35 S rDNA by RNA polymerase I in vitro. 218 53

Transcriptional promoters of mitochondrial DNA have diverged extensively in the course of mammalian evolution. Nevertheless, the transcriptional machinery and the overall mechanisms of transcriptional control and regulation seem to be conserved. We have compared the human and murine homologs of the major DNA-binding transcriptional activator, mitochondrial transcription factor 1 (mtTF1), with unexpected results. Both proteins have similar chromatographic and transcriptional properties and are the same size. Both recognize and bind sequences between -12 and -39 within their respective homologous promoters. However, the sequences that they recognize are markedly divergent; although the base pairs they contact are situated similarly or identically with respect to the transcriptional start site, sequence identity between the two species' contact points is less than 50%. Interestingly, the two proteins are functionally interchangeable; each can bind to the heterologous light-strand promoter and can activate transcription by the heterologous mitochondrial RNA polymerase. Thus, the RNA polymerase or some as yet undetected transcription factor, rather than mTF1, may determine the strict species specificity of mitochondrial transcription. Flexible DNA sequence recognition by mtTF1, on the other hand, may be a principal facilitating mechanism for rapid control sequence evolution.
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PMID:Flexible recognition of rapidly evolving promoter sequences by mitochondrial transcription factor 1. 262 67

We have extended an earlier observation that the TATA box for the nuclear GAL10 gene serves as a promoter for the mitochondrial RNA polymerase in in vitro transcription reactions (C. S. Winkley, M. J. Keller, and J. A. Jaehning, J. Biol. Chem. 260:14214-14223, 1985). In this work, we demonstrate that other nuclear genes also have upstream sequences that function in vitro as mitochondrial RNA polymerase promoters. These genes include the GAL7 and MEL1 genes, which are regulated in concert with the GAL10 gene, the sigma repetitive element, and the 2 microns plasmid origin of replication. We used in vitro transcription reactions to test a large number of nuclear DNA sequences that contain critical mitochondrial promoter sequences as defined by Biswas et al. (T. K. Biswas, J. C. Edwards, M. Rabinowitz, and G. S. Getz, J. Biol. Chem. 262:13690-13696, 1987). The results of these experiments allowed us to extend the definition of essential promoter elements. This extended sequence, -ACTATAAACGatcATAG-, was frequently found in the upstream regulatory regions of nuclear genes. On the basis of these observations, we hypothesized that either (i) a catalytic RNA polymerase related to the mitochondrial enzyme functions in the nucleus of the yeast cell or (ii) a DNA sequence recognition factor is shared by the two genetic compartments. By using cells deficient in the catalytic core of the mitochondrial RNA polymerase (rpo41-) and sensitive assays for transcripts initiating from the nuclear promoter sequences, we have conclusively ruled out a role for the catalytic RNA polymerase in synthesizing transcripts from all of the nuclear sequences analyzed. The possibility that a DNA sequence recognition factor functions in both the nucleus and the mitochondria remains to be tested.
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PMID:Use of yeast nuclear DNA sequences to define the mitochondrial RNA polymerase promoter in vitro. 267 67

In our previous work (Lisowsky et al. 1987; Lisowsky and Michaelis 1988) we have identified two nuclear pet genes of yeast that are required for mitochondrial transcription. In this report we show that one of these pet mutations, pet-ts798, maps in the RP041 gene encoding mitochondrial RNA polymerase. The temperature-sensitive lesion of mutant pet-ts798 can be suppressed by a second nuclear gene RF1023 (mtf1) when inserted into a high copy number plasmid. Our assumption that mtf1 codes for a 40 kDa mitochondrial transciription factor is supported by the fact that the cloned gene acts as an intergenic suppressor of a temperature-sensitive RNA polymerase mutant. A third nuclear gene (mtf2) for mitochondrial transcription was identified by analysing mutant pet-ts3504. The in vitro transcriptional activity of isolated mutant mitochondria is temperature sensitive suggesting the presence of an altered component of transcription inside mitochondria. The defect was confirmed by studies with a transcriptionally active DNA-protein complex and by testing the DNA-binding ability of mitochondrial proteins.
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PMID:Mutations in the genes for mitochondrial RNA polymerase and a second mitochondrial transcription factor of Saccharomyces cerevisiae. 269 37

We have isolated a cAMP-binding protein from highly purified yeast mitochondria by affinity chromatography. It is a lipophilic protein of molecular mass 45 000 Da, which is tightly membrane-bound and localized on the outer surface of the inner membrane. It can be solubilized in active form under mild conditions. The cAMP receptor resembles mitochondrial RNA polymerase prepared as described by Levens et al. [(1981) J. Biol. Chem. 256, 1474] in a surprisingly large number of properties including molecular mass. Comparison of the two proteins revealed that the polypeptide previously considered as RNA polymerase is, in fact, a mitochondrial cAMP receptor protein.
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PMID:Isolation of a cAMP receptor protein from yeast mitochondria (Mr 45000) and comparison with mitochondrial RNA polymerase (Mr 45000). 299 38


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