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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An E. coli mutant rpoA109 unable to support the growth of phage P2 produces DNA-dependent RNA polymerase with an altered alpha subunit. Histidine is substituted for leucine in one tryptic peptide from the mutant alpha subunit. The existence of only one rpoA gene within the E. coli chromosome is indicated.
Mol Gen Genet 1976 Apr 23
PMID:Identification of a mutation within the structural gene for the a subunit of DNA-dependent RNA polymerase of E. coli. 77 6

The analysis of tryptic peptides was performed on the unassembled as well as assembled form f alpha subunit of the DNA-dependent RNA polymerase from Escherichia coli. The peptide profiles obtained by Dowex 50 column chromatography of the unassembled alpha subunit prepared from cells, either pulse-labeled or continuously labeled with radioactive lysine or arginine, were essentially identical with those of the alpha subunit from intact RNA polymerase. The results suggest that newly synthesized free alpha subunit is assembled into the polymerase structure without any remarkable modifications. The number of lysine- and arginine-containing peaks were close to the values expected from the amino acid composition of alpha subunit assuming that the two alpha subunits in RNA polymerase core enzyme have identical primary structure.
Mol Gen Genet 1976 Jun 15
PMID:Peptide analysis of RNA polymerase alpha subunit from Escherichia coli: comparison of free with assembled form. 78 18

The transducing phage lambdarifd18 isolated by Kirschbaum and Konrad [(1973 J. Bacteriol. 116, 517-526] was found to carry structural genes for several 50S ribosomal proteins and 16S and 23S rRNA. It has previously been demonstrated [Kirschbaum & Scaife (1974) Mol. Gen. Genet. 132, 193-201] that this phage carries genes for the DNA-dependent RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase; EC 2.7.7.6) subunits beta and beta'. Thus, the region of the E. coli chromosome carried by lambdarifd18 contains a cluster of genes essential for transcription and translation.
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PMID:Cluster of genes in Escherichia coli for ribosomal proteins, ribosomal RNA, and RNA polymerase subunits. 110 Dec 64

A mutant of Escherichia coli K12 is described in which sigma and alpha subunits of the DNA-dependent RNA polymerase (EC 2.7.7.6) are produced at the rates much higher than in the normal strain. The rate of synthesis for sigma subunit was found to be at least 10-times higher, though the rapid degradation of sigma polypeptides accompanied with the accelerated synthesis precludes accurate estimation of the extent of hyperproduction. The alpha subunit synthesis was about 5-times higher in this mutant than in the control, and excess alpha polypeptides produced were as stable as the bulk of protein under the conditions employed. Genetic analyses of the mutant by conjugation and by transduction with phage P1 revealed that at least three distinct but closely linked mutations are responsible for hyperproduction of the sigma subunit; one (sig-1) is located very close to rif, and the others (sig-2 and sig-3) at the argH-bfe and metB regions, respectively. The results further indicate that the accelerated synthesis of alpha subunit is due to a mutation also located at the metB region. The present finding suggests that the synthesis of sigma subunit is subject to a complex control that can be affected by a number of cellular processes. The possible involvement of the core polymerase in determining the rate of synthesis of sigma subunit is discussed.
Mol Gen Genet 1975 Nov 24
PMID:Hyperproduction of the sigma subunit of RNA polymerase in a mutant of Escherichia coli. 110 14

Xenopus RNA polymerase III specifically initiates transcription on poly(dC)-tailed DNA templates in the absence of other class III transcription factors normally required for transcription initiation. In experimental analyses of transcription termination using DNA fragments with a 5S rRNA gene positioned downstream of the tailed end, only 40% of the transcribing polymerase molecules terminate at the normally efficient Xenopus borealis somatic-type 5S rRNA terminators; the remaining 60% read through these signals and give rise to runoff transcripts. We find that the nascent RNA strand is inefficiently displaced from the DNA template during transcription elongation. Interestingly, only polymerases synthesizing a displaced RNA terminate at the 5S rRNA gene terminators; when the nascent RNA is not displaced from the template, read-through transcripts are synthesized. RNAs with 3' ends at the 5S rRNA gene terminators are judged to result from authentic termination events on the basis of multiple criteria, including kinetic properties, the precise 3' ends generated, release of transcripts from the template, and recycling of the polymerase. Even though only 40% of the polymerase molecules ultimately terminate at either of the tandem 5S rRNA gene terminators, virtually all polymerases pause there, demonstrating that termination signal recognition can be experimentally uncoupled from polymerase release. Thus, termination is dependent on RNA strand displacement during transcription elongation, whereas termination signal recognition is not. We interpret our results in terms of a two-step model for transcription termination in which polymerase release is dependent on the fate of the nascent RNA strand during transcription elongation.
Mol Cell Biol 1992 May
PMID:Transcription termination by RNA polymerase III: uncoupling of polymerase release from termination signal recognition. 131 52

A member of the young PV Alu subfamily is detected in chimpanzee DNA showing that the PV subfamily is not specific to human DNA. This particular Alu is absent from the orthologous loci in both human and gorilla DNAs, indicating that PV subfamily members transposed within the chimpanzee lineage following the divergence of chimpanzee from both gorilla and human. These findings and previous reports describing the transpositional activity of other Alu sequences within the human, gorilla, and chimpanzee lineages provide phylogenetic evidence for the existence of multiple Alu source genes. Sequences surrounding this particular Alu resemble known transcriptional control elements associated with RNA polymerase III, suggesting a mechanism by which cis-acting elements might be acquired upon retrotransposition.
J Mol Evol 1992 Jul
PMID:Phylogenetic evidence for multiple Alu source genes. 132 66

We have determined that TPD3, a gene previously identified in a screen for mutants defective in tRNA biosynthesis, most likely encodes the A regulatory subunit of the major protein phosphatase 2A species in the yeast Saccharomyces cerevisiae. The predicted amino acid sequence of the product of TPD3 is highly homologous to the sequence of the mammalian A subunit of protein phosphatase 2A. In addition, antibodies raised against Tpd3p specifically precipitate a significant fraction of the protein phosphatase 2A activity in the cell, and extracts of tpd3 strains yield a different chromatographic profile of protein phosphatase 2A than do extracts of isogenic TPD3 strains. tpd3 deletion strains generally grow poorly and have at least two distinct phenotypes. At reduced temperatures, tpd3 strains appear to be defective in cytokinesis, since most cells become multibudded and multinucleate following a shift to 13 degrees C. This is similar to the phenotype obtained by overexpression of the protein phosphatase 2A catalytic subunit or by loss of CDC55, a gene that encodes a protein with homology to a second regulatory subunit of protein phosphatase 2A. At elevated temperatures, tpd3 strains are defective in transcription by RNA polymerase III. Consistent with this in vivo phenotype, extracts of tpd3 strains fail to support in vitro transcription of tRNA genes, a defect that can be reversed by addition of either purified RNA polymerase III or TFIIIB. These results reinforce the notion that protein phosphatase 2A affects a variety of biological processes in the cell and provide an initial identification of critical substrates for this phosphatase.
Mol Cell Biol 1992 Nov
PMID:Inactivation of the protein phosphatase 2A regulatory subunit A results in morphological and transcriptional defects in Saccharomyces cerevisiae. 132 68

Previously we have shown that nuclear extracts from mouse cells contain a heterogeneous group of polypeptides (p65, p80, p90, p100) which form distinct DNA-protein complexes on the 18 base-pair sequence element (termed Sal-box), which constitutes the murine rDNA transcription termination signal. These distinct proteins mediate cessation of RNA polymerase I (pol I) transcription elongation and release of the nascent RNA chains, indicating that they function as termination factor(s). Here, we report the biochemical analysis of the pol I-specific transcription termination factor TTFI. We show that the heterogeneity of TTFI is due to limited proteolysis of a larger, 130 kDa precursor protein (p130). The DNA-binding activity of p130 is strongly reduced as compared to the proteolytic derivatives, indicating that the DNA-binding domain is repressed within the full-length molecule. We have used limited proteolysis to purify and functionally characterize a TTFI core polypeptide (p50) which still specifically binds to the Sal-box target sequence and directs rDNA transcription termination. The equilibrium constant of purified p50 to bind specifically to DNA is 9 x 10(9) M-1. Additionally, we demonstrate that TTFI binds to DNA as a monomer and that binding induces DNA bending. This observation suggests that not only specific DNA-protein and protein-protein interactions but also conformational alterations of DNA may play a role in the termination process.
J Mol Biol 1992 Oct 05
PMID:Limited proteolysis unmasks specific DNA-binding of the murine RNA polymerase I-specific transcription termination factor TTFI. 140 80

We have exploited the Escherichia coli lac operator/repressor system as a means to regulate the expression of a mammalian tRNA gene in vivo and in vitro. An oligonucleotide containing a lac operator (lacO) site was cloned immediately upstream of a human serine amber suppressor (Su+) tRNA gene. Insertion of a single lac repressor binding site at position -1 or -32 relative to the coding region had no effect on the amount of functional tRNA made in vivo, as measured by suppression of a nonsense mutation in the E. coli chloramphenicol acetyltransferase gene following cotransfection of mammalian cells. Inclusion of a plasmid expressing the lac repressor in the transfections resulted in 75 to 98% inhibition of suppression activity of lac operator-linked tRNA genes but had no effect on expression of the wild-type gene. Inhibition could be quantitatively relieved with the allosteric inducer isopropylthio-beta-D-galactoside (IPTG). Similarly, transcription in vitro of lac operator-linked tRNA genes in HeLa cell extracts was repressed in the presence of lac repressor, and this inhibition was reversible with IPTG. These results demonstrate that the bacterial lac operator/repressor system can be used to reversibly control the expression of mammalian genes that are transcribed by RNA polymerase III.
Mol Cell Biol 1992 Oct
PMID:Regulated expression of a mammalian nonsense suppressor tRNA gene in vivo and in vitro using the lac operator/repressor system. 140 20

The SRP1-1 mutation is an allele-specific dominant suppressor of temperature-sensitive mutations in the zinc-binding domain of the A190 subunit of Saccharomyces cerevisiae RNA polymerase I (Pol I). We found that it also suppresses temperature-sensitive mutations in the zinc-binding domain of the Pol I A135 subunit. This domain had been suggested to be in physical proximity to the A190 zinc-binding domain. We have cloned the SRP1 gene and determined its nucleotide sequence. The gene encodes a protein of 542 amino acids consisting of three domains: the central domain, which is composed of eight (degenerate) 42-amino-acid contiguous tandem repeats, and the surrounding N-terminal and C-terminal domains, both of which contain clusters of acidic and basic amino acids and are very hydrophilic. The mutational alteration (P219Q) responsible for the suppression was found to be in the central domain. Using antibody against the SRP1 protein, we have found that SRP1 is mainly localized at the periphery of the nucleus, apparently more concentrated in certain regions, as suggested by a punctate pattern in immunofluorescence microscopy. We suggest that SRP1 is a component of a larger macromolecular complex associated with the nuclear envelope and interacts with Pol I either directly or indirectly through other components in the structure containing SRP1.
Mol Cell Biol 1992 Dec
PMID:Cloning and characterization of SRP1, a suppressor of temperature-sensitive RNA polymerase I mutations, in Saccharomyces cerevisiae. 144 93


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