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At least 937 records · Page 52Linked to original sources
PubMed1975

Regulation of stable RNA synthesis and ppGpp levels in growing cells of Escherichia coli.

Under the balanced condition of growth of E. coli cells, no distinct difference is observed in stable RNA and protein synthesis between CP78 (rel+) and CP79 (rel minus), whereas a considerable difference is present in RNA accumulation between NF161 (rel+) and NF162 (rel minus), where NF161 smaller than NF162. The RNA content of NF161 is lower than that of NF162 in four different cultures with different growth rates. These two sets of isogenic pairs of rel+ and rel minus strains are commonly used in the study of rel gene function; however, NF161 is a mutant in the spoT gene whose product may be responsible for the degradation of ppGpp. The basal levels of ppGpp in these four strains growing with three different growth rates were examined: NF161 (rel+ spoT minus) has a much higher content of ppGpp than do other strains. Furthermore, the contents of ppGpp tend to be lower when the above four strains are growing at a faster rate. Thus a close correlation seems to exist between the content of RNA and the basal level of ppGpp under the condition of balanced growth.

Adenosine Triphosphate↗
PubMed1982

Regulation of ribosomal RNA cistron number in a strain of Neurospora crassa with a duplication of the nucleolus organizer region.

Some progeny from a cross of the translocation mutant T(VL leads to IVL)AR33 with wild-type Neurospora crassa are double nucleolus organizer (DNO) strains, usually displaying two distinct nucleolus organizer regions. The DNO strain is sterile but displays the same growth response as normal laboratory strains of Neurospora. We used DNA-DNA hybridization techniques to quantify the number of rRNA cistrons in the DNO mutant and its vegetative progeny. Comparisons of the rate of hybridization of genomic DNA from the parental AR33 strain and from the DNO strain showed that hybridization was more rapid for the DNO strain than for the parental strain. Successive vegetative progeny of the DNO strain displayed hybridization rates intermediate to those of the original DNO strain and the parental single nucleolus strain, indicating that the number of rRNA cistrons had decreased during vegetative propagation. Estimates of rRNA cistron number obtained from comparisons of the amount of single copy DNA and rDNA hybridized to genomic DNO and AR33 DNA at saturation indicate that the parental AR33 strain contains 225 copies of the rRNA repeat unit while the DNO strain has approx. 440 copies. The number of rRNA cistrons decreases gradually in the successive vegetative progeny, approximating the parental haploid value by the eleventh vegetative transfer.

Cell Nucleolus↗
PubMed1995

Guanosine tetraphosphate as a global regulator of bacterial RNA synthesis: a model involving RNA polymerase pausing and queuing.

A recently reported comparison of stable RNA (rRNA, tRNA) and mRNA synthesis rates in ppGpp-synthesizing and ppGpp-deficient (delta relA delta spoT) bacteria has suggested that ppGpp inhibits transcription initiation from stable RNA promoters, as well as synthesis of (bulk) mRNA. Inhibition of stable RNA synthesis occurs mainly during slow growth of bacteria when cytoplasmic levels of ppGpp are high. In contrast, inhibition of mRNA occurs mainly during fast growth when ppGpp levels are low, and it is associated with a partial inactivation of RNA polymerase. To explain these observations it has been proposed that ppGpp causes transcriptional pausing and queuing during the synthesis of mRNA. Polymerase queuing requires high rates of transcription initiation in addition to polymerase pausing, and therefore high concentrations of free RNA polymerase. These conditions are found in fast growing bacteria. Furthermore, the RNA polymerase queues lead to a promoter blocking when RNA polymerase molecules stack up from the pause site back to the (mRNA) promoter. This occurs most frequently at pause sites close to the promoter. Blocking of mRNA promoters diverts RNA polymerase to stable RNA promoters. In this manner ppGpp could indirectly stimulate synthesis of stable RNA at high growth rates. In the present work a mathematical analysis, based on the theory of queuing, is presented and applied to the global control of transcription in bacteria. This model predicts the in vivo distribution of RNA polymerase over stable RNA and mRNA genes for both ppGpp-synthesizing and ppGpp-deficient bacteria in response to different environmental conditions. It also shows how small changes in basal ppGpp concentrations can produce large changes in the rate of stable RNA synthesis.

Bacteria↗
PubMed1995

Acute and chronic amphetamine treatments differently regulate neuropeptide messenger RNA levels and Fos immunoreactivity in rat striatal neurons.

Repeated administration of amphetamine results in the well known phenomenon of reverse tolerance or sensitization. However, little is known about cellular and molecular mechanisms underlying acute versus chronic response to amphetamine. In this paper, we investigated the effects of acute (1.5 or 5 mg/kg) and chronic (5 mg/kg/day for 14 days) amphetamine treatment on locomotor activity, stereotypy, Fos immunoreactivity and messenger RNA levels of molecules implicated in dopamine transmission in the rat striatum and substantia nigra. In agreement with other studies, acute amphetamine induced a dose dependent increase in locomotor activity and stereotypy. Also, a comparison between the behavior observed after the first injection and the last injection of amphetamine in chronically treated rats showed sensitization as demonstrated by a higher rating of stereotypy. We have found that acute and chronic amphetamine treatments differently modulate the activity of several output neurons. A double labeling procedure with Fos immunohistochemistry coupled with in situ hybridization demonstrated that acute amphetamine treatment induces Fos immunoreactivity predominantly in striatal neurons expressing substance P messenger RNA (77.07 +/- 1.42%). Only 32.6 +/- 2.07% of Fos immunoreactive neurons expressed preproenkephalin A messenger RNA. In chronic amphetamine treated rats, 56.21 +/- 1.32% of the Fos immunoreactive neurons expressed substance P messenger RNA while 52.12 +/- 1.84% expressed preproenkephalin A messenger RNA. Statistical analysis revealed that this difference is mainly due to a decrease in the density of substance P immunoreactive neurons in chronically treated rats in comparison to acute. Amphetamine treatments induced Fos immunoreactivity in the substantia nigra in non-dopamine neurons. As measured by quantitative in situ hybridization, acute amphetamine induced an increase in substance P, preproenkephalin A and dynorphin messenger RNA levels (+23 +/- 0.05%, +45 +/- 0.07% and +24 +/- 0.05%, respectively). No difference in these increases was observed in relation with the dose injected (1.5 or 5 mg/kg). Chronic amphetamine treatment enhanced only substance P and dynorphin messenger RNA levels (+23 +/- 0.04% and +42 +/- 0.04%, respectively). Neither acute nor chronic amphetamine treatment had any effects on D1 or D2 dopamine receptor messenger RNA levels. Our main conclusions are: (1) in acutely treated rats Fos is essentially expressed by substance P neurons; (2) in chronically treated rats, Fos immunoreactivity is expressed by the two efferent striatal populations (i.e. preproenkephalin A and substance P neurons) and the number of Fos immunoreactive neurons is reduced as compared with acute; (3) neuropeptide messenger RNA levels, but not dopamine receptor messenger RNAs, are affected in the response to acute or chronic treatment with amphetamine.

Amphetamine↗
PubMed1997

Phosphorylation of the human La antigen on serine 366 can regulate recycling of RNA polymerase III transcription complexes.

The human La antigen is an RNA-binding protein that facilitates transcriptional termination and reinitiation by RNA polymerase III. Native La protein fractionates into transcriptionally active and inactive forms that are unphosphorylated and phosphorylated at serine 366, respectively, as determined by enzymatic and mass spectrometric analyses. Serine 366 comprises a casein kinase II phosphorylation site that resides within a conserved region in the La proteins from several species. RNA synthesis from isolated transcription complexes is inhibited by casein kinase II-mediated phosphorylation of La serine 366 and is reversible by dephosphorylation. This work demonstrates a novel mechanism of transcriptional control at the level of recycling of stable transcription complexes.

Autoantigens↗
PubMed2002

The alpha(1A) subunits of rat brain calcium channels are developmentally regulated by alternative RNA splicing.

Calcium influx through voltage-gated calcium channels governs important aspects of CNS development. Multiple alternative splicings of the pore-forming alpha(1) subunits have been evidenced in adult brain but little information about their expression during ontogenesis is presently available. The aim of this study was to focus on the expression of three rat voltage-gated calcium channel alpha(1A) splice variants (alpha(1A-a), alpha(1A-b) and alpha(1A-EFe)) during brain ontogenesis in vivo. Using a reverse transcription-polymerase chain reaction strategy, we found that the three isoforms have different timings of development throughout the brain: alpha(1A-b) is expressed from embryonic to the adult stage, alpha(1A--EFe) is restricted to the embryonic period whereas alpha(1A-a) is expressed only postnatally. In situ hybridization indicated that alpha(1A-a) and alpha(1A-b) isoforms develop with different regional and cellular patterns. In hippocampus and cerebellum, alpha(1A-b) represented the predominant isoform at all developmental stages. Taken together, these data reveal that alternative RNA splicing may modulate the alpha(1A) calcium channel properties during development.

Alternative Splicing↗
PubMed2003

The response regulator BvgA and RNA polymerase alpha subunit C-terminal domain bind simultaneously to different faces of the same segment of promoter DNA.

Examination of the binding of FeBABE-conjugated BvgA to the fha promoter of Bordetella pertussis has revealed that three dimers, formed by head-to-head association of monomers, bind one face of the DNA helix from the inverted-heptad primary binding site to the -35 region. The orientation of BvgA monomers within the dimers is the same as that recently demonstrated by X-ray crystallographic methods for a dimer of the C-terminal domain of NarL bound to DNA. Use of FeBABE conjugates of RNAP alpha subunit C-terminal domain showed that binding of this domain is linearly coincident with binding of the BvgA dimers, but to a different helical face. These results reveal a previously undescribed mode of interaction between RNAP alpha-CTD and a transcriptional activator.

Bacterial Proteins↗
PubMed1977

Regulation of ribosomal RNA synthesis in mammalian cells: effect of toyocamycin.

The present study shows that the antitumor agent toyocamycin (4-amino-5-cyano-7beta-D-ribofuranosylpyrrolo(2-3d)pyrimidine) affects rRNA transcription in Ehrlich ascites cells. This action of the antibiotic is dependent on the amino acid composition of the cell culture medium. In cells incubated in a medium rich in amino acids, the high transcription rate of rRNA is lowered by the addition of 2 X 10(-6) M toyocamycin, while in amino acid starved cells the decreased level of rRNA synthesis remains unaffected. Processing of the 45S rRNA precursor is markedly inhibited by toyocamycin in cells incubated in either medium, indicating that the uptake of the drug is unimpaired by amino acid starvation. Toyocamycin does not affect RNA polymerase I (RNA nucleotidyltransferase EC 2.7.7.6) activity when added to in vitro assay systems derived from cells grown in complete or in amino acid deficient media. The drug prevents the activation of rRNA synthesis following the refeeding of amino acid starved cells without affecting the stimulation of protein synthesis.

Amino Acids↗
PubMed1976

Regulation of ribosomal RNA synthesis and processing during inhibition of protein synthesis by 1,3-bis(2-chloroethyl)-1-nitrosourea.

The antineoplastic agent BCNU (1,3-bis(2-chloroethyl)-1nitrosourea) at a concentration of 25 mug/ml inhibits initiation of protein synthesis in HeLa cells. At this low concentration of the drug, the rate of synthesis of 45S ribosomal precursor RNA (pre-rRNA) is selectively inhibited without a marked inhibition of nucleoplasmic RNA. The inhibitory effects of the drug are readily reversible upon removal of BCNU from the growth medium. Pulse-chase analysis of the labeled nucleolar RNA in sucrose-gradients and acrylamide gels indicated that the 45S pre-rRNA synthesized before the addition of BCNU matures normally in the presence of the inhibitor. However, the processing of precursor RNA molecules synthesized following the addition of the drug is inhibited when incubation is continued on in the presence of 25 mug/ml BCNU. Since the formation of mature ribosomes is blocked by BCNU, the data would suggest that the effectiveness of the drug as a potent cell growth inhibitor may result from its inhibition of ribosome formation induced by inhibition of protein synthesis.

Carmustine↗
PubMed1987

Retroviral-mediated transfer of genomic globin genes leads to regulated production of RNA and protein.

A high-titer amphotropic retroviral vector containing the neomycin resistance gene and a hybrid gamma-beta genomic human globin gene has been constructed. Mouse erythroleukemia cells infected with this virus were found to contain the full transcriptional unit of the transferred human globin gene by Southern blot analysis. These cells contain normally initiated, spliced, and terminated human globin mRNA. The human globin mRNA level increased 5- to 10-fold upon induction of the mouse erythroleukemia cells. Human globin chains were produced but only in a fraction of the cells as detected by immunofluorescent staining. A similar retrovirus containing a human beta-globin gene was used to transduce mouse erythroleukemia cells resulting in much higher levels of human globin synthesis than detected in mouse erythroleukemia cells transduced with the gamma-beta globin virus.

Animals↗
PubMed1997

The position dependence of translational regulation via RNA-RNA and RNA-protein interactions in the 5'-untranslated region of eukaryotic mRNA is a function of the thermodynamic competence of 40 S ribosomes in translational initiation.

Cap proximity is a requirement to enable secondary structures and RNA-binding proteins to repress translational initiation via the 5'-untranslated region (5'-UTR) of mammalian mRNAs. We show that in Saccharomyces cerevisiae, unlike mammalian cells, the in vitro translational repressive effect of the mammalian iron regulatory protein 1 (IRP1) is independent of the site of its target in the 5'-UTR, the iron-responsive element (IRE). In vitro studies demonstrate that the binding affinity of IRP1 is also unaffected by the position of the IRE. Using IRE loop mutants, we observe an almost complete loss of IRP1-dependent repression in yeast concomitant with a 150-fold reduction in binding affinity for the IRE target. This mirrors the natural quantitative range of iron-induced adjustment of IRE/IRP1 affinity in mammalian cells. By enhancing the stability of the IRE stem-loop, we also show that its intrinsic folding energy acts together with the binding energy of IRP1 to give an additive capacity to restrict translational initiation. An IRE.IRP1 complex in a cap-distal position in yeast blocks scanning 40 S ribosomes on the 5'-UTR. It follows that the position effect of mammalian site-specific translational repression is dictated by the competence of the mammalian preinitiation complex to destabilize inhibitory structures at different steps of the initiation process.

Base Sequence↗