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

---

Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The DNA-dependent RNA polymerase present in the mitochondria of Saccharomyces cerevisiae has been solubilized using a 0.5 M KCI solution, and the soluble enzyme has been purified. Two forms of mitochondrial enzyme were obtained; they differ in their template specificity and metal-ion dependency. The mitochondrial RNA polymerase also differs from enzyme obtained from the nucleus with respect to antibiotic sensitivity and template specificity. Only the nuclear enzyme is sensitive to alpha-amanitin inhibition. The relative activities of the isolated nuclear and mitochondrial polymerases toward their homologous DNAs are consistent with their in vivo functions. The possibilities of bacterial- and nuclear-enzyme contamination of the mitochondrial enzyme preparation have been ruled out. RNA polymerase activity in two petite mutants has been studied. Isolated mitochondria from a petite mutant with no detectable mitochondrial DNA has greatly diminished mitochondrial DNA-dependent RNA polymerase activity, while a petite mutant with only a small change in mitochondrial DNA base composition has normal amounts of enzyme.
...
PMID:DNA-dependent RNA polymerase from yeast mitochondria. 527 4

We have determined transcriptional initiation sites for the ATPase subunit 9 gene on the yeast mitochondrial genome. Using S1 nuclease mapping, in vitro capping of primary transcripts with GTP and guanylyl transferase, and in vitro transcription analysis with purified mitochondrial RNA polymerase, we find the major site of transcriptional initiation to be at a point 630 nucleotides upstream of the coding region for the gene. In addition, we find much lower levels of initiation at a second site 78 nucleotides downstream of the first. Both initiation sites occur at the same position within a nonanucleotide sequence which we have previously found associated with initiation of rRNA synthesis. This work further supports the notion that this nonanucleotide sequence is an integral component of mitochondrial promoters and indicates that the same RNA polymerase is used for transcription of both mRNA and rRNA in yeast mitochondria.
...
PMID:Initiation of transcription of the yeast mitochondrial gene coding for ATPase subunit 9. 623 27

We have developed an in vitro transcription system for yeast mitochondrial rRNA genes. Using highly purified yeast mitochondrial RNA polymerase and bacterial plasmids carrying DNA segments containing the mitochondrial rRNA sites of transcriptional initiation, we have been able to demonstrate correct initiation of transcription in vitro. By directly sequencing the transcription products, we show that transcription in vitro of both the 14S and 21S rRNAs is initiated at precisely the same site as it is in vivo. Transcription of the rRNA genes is highly sensitive to ionic strength and RNA polymerase concentration. Additional factors or modified conditions may be necessary to permit accurate transcription of mitochondrial protein genes.
...
PMID:Analysis of transcriptional initiation of yeast mitochondrial DNA in a homologous in vitro transcription system. 676 Sep 88

Yeast mitochondrial RNA polymerase is a nuclear-coded protein of approximately 90,000 daltons comprised of two 45,000-dalton subunits of pI 6.9 to 7.0. To investigate the nature of the initial translation product of the RNA polymerase, we have analyzed those products of a cell-free translation system directed by yeast RNA that are immunoreactive with antibodies to the 45,000-dalton peptide of polymerase. A precursor of one or more of the subunits of the polymerase, 2,000 daltons later than the mature product, has been characterized using immunoreaction, immunocompetition, and peptide digestion. The role of transcription of the polymerase gene in catabolite repression of mitochondrial development has been investigated by analyzing the changes in cell-free synthesis of the RNA polymerase precursor during glucose and raffinose growth. The results indicate an increase in precursor synthesis and probably in the corresponding transcript abundance during glucose derepression. In contrast, the precursor is present at high levels until stationary phase during raffinose growth. These data indicate the involvement of increased transcription of the polymerase gene in the process of derepression.
...
PMID:The biogenesis and regulation of yeast mitochondria RNA polymerase. 704 Mar 74

Human mitochondrial 16 S rRNA 3'-end formation requires a tridecamer template sequence and a trans-acting protein of approximately 34 kDa. This protein binds tightly to its target sequence and further analysis of the protein-DNA complex revealed that the DNA is bent. Either T3, T7, Escherichia coli, or yeast mitochondrial RNA polymerase produced transcripts mapping at this termination site. With these heterologous RNA polymerase, RNA 3'-end formation was detected only in the transcription polarity opposite that of mitochondrial rRNA synthesis; the efficiency of termination in the homologous human RNA polymerase system is approximately 2-fold greater in this same opposite polarity. These results suggested the possible importance of biased bipolar transcription termination in vivo. For wild-type mtDNA, the apparent relative efficiency of termination in vivo reflected the values determined in vitro. Examination of a pathogenic human mtDNA mutation known to result in impaired termination in vitro showed no significant differences in relative transcript abundances in vivo, despite a loss of in vitro termination efficiency in both directions. Recently, six additional mitochondrial disease-associated point mutations have been reported that cluster at the human mitochondrial transcription termination site. None of these resulted in significantly impaired transcription termination in vitro.
...
PMID:Human mitochondrial transcription termination exhibits RNA polymerase independence and biased bipolarity in vitro. 752 79

Critical features of the mitochondrial leading-strand DNA replication origin are conserved from Saccharomyces cerevisiae to humans. These include a promoter and a downstream GC-rich sequence block (CSBII) that encodes rGs within the primer RNA. During in vitro transcription at yeast mitochondrial replication origins, there is stable and persistent RNA-DNA hybrid formation that begins at the 5' end of the rG region. The short rG-dC sequence is the necessary and sufficient nucleic acid element for establishing stable hybrids, and the presence of rGs within the RNA strand of the RNA-DNA hybrid is required. The efficiency of hybrid formation depends on the length of RNA synthesized 5' to CSBII and the type of RNA polymerase employed. Once made, the RNA strand of an RNA-DNA hybrid can serve as an effective primer for mitochondrial DNA polymerase. These results reveal a new mechanism for persistent RNA-DNA hybrid formation and suggest a step in priming mitochondrial DNA replication that requires both mitochondrial RNA polymerase and an rG-dC sequence-specific event to form an extensive RNA-DNA hybrid.
...
PMID:A persistent RNA-DNA hybrid is formed during transcription at a phylogenetically conserved mitochondrial DNA sequence. 752 31

The yeast mitochondrial RNA polymerase is composed of two nuclear encoded subunits, a catalytic core (Rpo41p), which resembles the enzymes from bacteriophage T7 and T3, and a specificity factor required for promoter recognition (Mtf1p), which is similar to members of the eubacterial sigma factor family. Using mitochondrial RNA polymerase reconstituted from highly purified subunits, we have determined that Rpo41p and Mtf1p interact to form a holoenzyme in solution prior to DNA binding and promoter recognition. We analyzed the composition of the polymerase during and after the initiation of transcription and found that, like the eubacterial sigma factors, Mtf1p is released after initiation and is available to catalyze transcription on a second template. By analyzing gel mobility shift complexes of the RNA polymerase and DNA at different stages of the transcription reaction, we found that both subunits were associated with DNA prior to initiation and after the formation of two phosphodiester bonds. After the formation of a 13-nucleotide transcript, Mtf1p is no longer associated with Rpo41p on the DNA. These data establish that Mtf1p is functionally as well as structurally similar to eubacterial sigma factors.
...
PMID:Release of the yeast mitochondrial RNA polymerase specificity factor from transcription complexes. 792 82

Yeast mitochondrial transcript and gene product abundance has been observed to increase upon release from glucose repression, but the mechanism of regulation of this process has not been determined. We report a kinetic analysis of this phenomenon, which demonstrates that the abundance of all classes of mitochondrial RNA changes slowly relative to changes observed for glucose-repressed nuclear genes. Several cell doublings are required to achieve the 2- to 20-fold-higher steady-state levels observed after a shift to a nonrepressing carbon source. Although we observed that in some yeast strains the mitochondrial DNA copy number also increases upon derepression, this does not seem to play the major role in increased RNA abundance. Instead we found that three- to sevenfold increases in RNA synthesis rates, measured by in vivo pulse-labelling experiments, do correlate with increased transcript abundance. We found that mutations in the SNF1 and REG1 genes, which are known to affect the expression of many nuclear genes subject to glucose repression, affect derepression of mitochondrial transcript abundance. These genes do not appear to regulate mitochondrial transcript levels via regulation of the nuclear genes RPO41 and MTF1, which encode the subunits of the mitochondrial RNA polymerase. We conclude that a nuclear gene-controlled factor(s) in addition to the two RNA polymerase subunits must be involved in glucose repression of mitochondrial transcript abundance.
...
PMID:Glucose repression of yeast mitochondrial transcription: kinetics of derepression and role of nuclear genes. 828 97

Despite the striking similarities of RNA polymerases and transcription signals shared by eubacteria, archaebacteria and eukaryotes, there has been little indication that transcription in mitochondria is related to any previously characterized model. Only in yeast has the subunit structure of the mitochondrial RNA polymerase been determined. The yeast enzyme is composed of a core related to polymerases from bacteriophage T7 and T3, and a promoter recognition factor similar to bacterial sigma factors. Soluble systems for studying mitochondrial transcript initiation in vitro have been described from several organisms, and used to determine consensus sequences at or near transcription start sites. Comparison of these sequences from fungi, plants, and amphibians with the T7/T3 promoter suggests some intriguing similarities. Mammalian mitochondrial promoters do not fit this pattern but instead appear to utilize upstream sites, the target of a transcriptional stimulatory factor, to position the RNA polymerase. The recent identification of a possible homologue of the mammalian upstream factor in yeast mitochondria may indicate that a pattern will eventually be revealed relating the transcriptional machineries of all eukaryotic mitochondria.
...
PMID:Mitochondrial transcription: is a pattern emerging? 849 87

The nuclear CBP2 gene encodes a protein essential for the splicing of a mitochondrial group I intron in Saccharomyces cerevisiae. This intron (bI5) is spliced autocatalytically in the presence of high concentrations of magnesium and monovalent salt but requires the Cbp2 protein for splicing under physiological conditions. Addition of Cbp2 during RNA synthesis permitted cotranscriptional splicing. Splicing did not occur in the transcription buffer in the absence of synthesis. The Cbp2 protein appeared to modify the folding of the intron during RNA synthesis: pause sites for RNA polymerase were altered in the presence of the protein, and some mutant transcripts that did not splice after transcription did so during transcription in the presence of Cbp2. Cotranscriptional splicing also reduced hydrolysis at the 3' splice junction. These results suggest that Cbp2 modulates the sequential folding of the ribozyme during its synthesis. In addition, splicing during transcription led to an increase in RNA synthesis with both T7 RNA polymerase and mitochondrial RNA polymerase, implying a functional coupling between transcription and splicing.
...
PMID:Cotranscriptional splicing of a group I intron is facilitated by the Cbp2 protein. 852 64


<< Previous 1 2 3 4 5 6 7 Next >>

---