Evidence for a nuclear passage of nascent polypeptide-associated complex subunits in yeast

2001 ◽  
Vol 114 (14) ◽  
pp. 2641-2648
Author(s):  
Jacqueline Franke ◽  
Barbara Reimann ◽  
Enno Hartmann ◽  
Matthias Köhler ◽  
Brigitte Wiedmann
Keyword(s):  
Transcriptional Regulation ◽  
Steady State ◽  
Fluorescence Microscopy ◽  
Nuclear Import ◽  
Cell Fractionation ◽  
Active Process ◽  
Ribosomal Subunits ◽  
State Equilibrium ◽  
Nascent Polypeptide ◽  
Ribosome Binding

The nascent polypeptide-associated complex (NAC) has been found quantitatively associated with ribosomes in the cytosol by means of cell fractionation or fluorescence microscopy. There have been reports, however, that single NAC subunits may be involved in transcriptional regulation. We reasoned that the cytosolic location might only reflect a steady state equilibrium and therefore investigated the yeast NAC proteins for their ability to enter the nucleus. We found that single subunits of yeast NAC can indeed be transported into the nucleus and that this transport is an active process depending on different nuclear import factors. Translocation into the nucleus was only observed when binding to ribosomes was inhibited. We identified a domain of the ribosome-binding NAC subunit essential for nuclear import via the importin Kap123p/Pse1p-dependent import route. We hypothesize that newly translated NAC proteins travel into the nucleus to bind stoichiometrically to ribosomal subunits and then leave the nucleus together with these subunits to concentrate in the cytosol.

scholarly journals A cell cycle analysis of growth-related genes expressed during T lymphocyte maturation.

1990 ◽  
Vol 111 (6) ◽  
pp. 2693-2701 ◽  
Author(s):  
J N Feder ◽  
C J Guidos ◽  
B Kusler ◽  
C Carswell ◽  
D Lewis ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcriptional Regulation ◽  
Steady State ◽  
T Lymphocyte ◽  
Ribonucleotide Reductase ◽  
Cellular Proliferation ◽  
Rnase Protection Assay ◽  
Minor Component ◽  
Mrna Levels ◽  
Rnase Protection

Fetal liver or bone marrow-derived T lymphocyte precursors undergo extensive, developmentally regulated proliferation in response to inductive signals from the thymic microenvironment. We have used neonatal mouse thymocytes size-separated by centrifugal elutriation to study the cell cycle stage-specific expression of several genes associated with cell proliferation. These include genes involved in the biosynthesis of deoxyribonucleotide precursors, such as dihydrofolate reductase (DHFR), thymidylate synthase (TS), and the M1 and M2 subunits of ribonucleotide reductase, as well as c-myc, a cellular oncogene of unknown function. Using nuclear run-on assays, we observed that the transcription rates for these genes, with the exception of TS, are essentially invariant not only throughout the cell cycle in proliferating cells, but also in noncycling (G0) cells. The TS gene showed a transient increase in transcription rate in cells which bordered between a proliferating and nonproliferating status. Studies of an elutriated T cell line, S49.1, yielded similar results, indicating that the process of immortalization has not affected the transcriptional regulation of these genes. Analysis of steady-state mRNA levels using an RNase protection assay demonstrated that the levels of DHFR and TS mRNA accumulate as thymocytes progress through the cell cycle. In contrast, only the M2 subunit of ribonucleotide reductase showed cyclic regulation. Finally, in contrast to cultured cell models, we observed an abrupt fivefold increase in the steady-state level of c-myc mRNA in the transition from G1 to S-phase. We conclude from these studies that the transcriptional regulation of specific genes necessary for cellular proliferation is a minor component of the developmental modulation of the thymocyte cell cycle.

Steady-state and time-resolved two-photon fluorescence microscopy: a versatile tool for probing cellular environment and function

2007 ◽  
Vol 76 (3) ◽  
pp. C115-C121 ◽  
Author(s):  
Stefan Denicke ◽  
Jan-Eric Ehlers ◽  
Raluca Niesner ◽  
Stefan Quentmeier ◽  
Karl-Heinz Gericke
Keyword(s):  
Steady State ◽  
Fluorescence Microscopy ◽  
Time Resolved ◽  
Two Photon ◽  
Cellular Environment ◽  
Versatile Tool ◽  
And Function ◽  
Two Photon Fluorescence ◽  
Photon Fluorescence

scholarly journals THE RICH AND THE POOR IN A SIMPLE MODEL OF GROWTH AND DISTRIBUTION

2016 ◽  
Vol 20 (7) ◽  
pp. 1934-1952 ◽  
Author(s):  
Kirill Borissov
Keyword(s):  
Economic Growth ◽  
Steady State ◽  
Simple Model ◽  
Disposable Income ◽  
State Equilibrium ◽  
Positional Concerns ◽  
The Poor ◽  
The Rich ◽  
Intertemporal Equilibrium ◽  
Unique Steady State

We consider a model of economic growth with altruistic agents who care about their consumption and the disposable income of their offspring. The agents' consumption and the offspring's disposable income are subject to positional concerns. We show that, if the measure of consumption-related positional concerns is sufficiently low and/or the measure of offspring-related positional concerns is sufficiently high, then there is a unique steady-state equilibrium, which is characterized by perfect income and wealth equality, and all intertemporal equilibira converge to it. Otherwise, in steady-state equilibria, the population splits into two classes, the rich and the poor; under this scenario, in any intertemporal equilibrium, all capital is eventually owned by the households that were the wealthiest from the outset and all other households become poor.

scholarly journals Leaderless mRNAs Bind 70S Ribosomes More Strongly than 30S Ribosomal Subunits in Escherichia coli

2002 ◽  
Vol 184 (23) ◽  
pp. 6730-6733 ◽  
Author(s):  
Sean M. O'Donnell ◽  
Gary R. Janssen
Keyword(s):  
Escherichia Coli ◽  
Translation Initiation ◽  
Primer Extension ◽  
Ribosomal Subunits ◽  
Ribosome Binding ◽  
Initiation Factors ◽  
Translation Initiation Factors

ABSTRACT By primer extension inhibition assays, 70S ribosomes bound with higher affinity, or stability, than did 30S subunits to leaderless mRNAs containing AUG or GUG start codons. Addition of translation initiation factors affected ribosome binding to leaderless mRNAs. Our results suggest that translation of leaderless mRNAs might initiate through a pathway involving 70S ribosomes or 30S subunits lacking IF3.

scholarly journals Genotype-dependent and non-gradient patterns of RSV gene expression

2019 ◽  
Author(s):  
Felipe-Andrés Piedra ◽  
Xueting Qiu ◽  
Michael N. Teng ◽  
Vasanthi Avadhanula ◽  
Annette A. Machado ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcriptional Regulation ◽  
Steady State ◽  
Transcription Initiation ◽  
Mrna Levels ◽  
Viral Pathogen ◽  
Negative Strand ◽  
Gene Start ◽  
Syncytial Virus ◽  
Conserved Gene

AbstractRespiratory syncytial virus (RSV) is a nonsegmented negative-strand (NNS) RNA virus and a leading cause of severe lower respiratory tract illness in infants and the elderly. Transcription of the ten RSV genes proceeds sequentially from the 3’ promoter and requires conserved gene start (GS) and gene end (GE) signals. Previous studies using the prototypical GA1 genotype Long and A2 strains have indicated a gradient of gene transcription. However, recent reports show data that appear inconsistent with a gradient. To better understand RSV transcriptional regulation, mRNA abundances from five RSV genes were measured by quantitative real-time PCR (qPCR) in three cell lines and cotton rats infected with virus isolates belonging to four different genotypes (GA1, ON, GB1, BA). Relative mRNA levels reached steady-state between four and 24 hours post-infection. Steady-state patterns were genotype-specific and non-gradient, where mRNA levels from the G (attachment) gene exceeded those from the more promoter-proximal N (nucleocapsid) gene across isolates. Transcript stabilities could not account for the non-gradient patterns observed, indicating that relative mRNA levels more strongly reflect transcription than decay. While the GS signal sequences were highly conserved, their alignment with N protein in the helical ribonucleocapsid, i.e., N-phase, was variable, suggesting polymerase recognition of GS signal conformation affects transcription initiation. The effect of GS N-phase on transcription efficiency was tested using dicistronic minigenomes. Ratios of minigenome gene expression showed a switch-like dependence on N-phase with a period of seven nucleotides. Our results indicate that RSV gene expression is in part sculpted by polymerases that initiate transcription with a probability dependent on GS signal N-phase.Author SummaryRSV is a major viral pathogen that causes significant morbidity and mortality, especially in young children. Shortly after RSV enters a host cell, transcription from its nonsegmented negative-strand (NNS) RNA genome starts at the 3’ promoter and proceeds sequentially. Transcriptional attenuation is thought to occur at each gene junction, resulting in a gradient of gene expression. However, recent studies showing non-gradient levels of RSV mRNA suggest that transcriptional regulation may have additional mechanisms. We show using RSV isolates belonging to four different genotypes that gene expression is genotype-dependent and one gene (the G or attachment gene) is consistently more highly expressed than an upstream neighbor. We hypothesize that variable alignment of highly conserved gene start (GS) signals with nucleoprotein (i.e., variable GS N-phase) can affect transcription and give rise to non-gradient patterns of gene expression. We show using dicistronic RSV minigenomes wherein the reporter genes differ only in the N-phase of one GS signal that GS N-phase affects gene expression. Our results suggest the existence of a novel mechanism of transcriptional regulation that might play a role in other NNS RNA viruses.

scholarly journals Differential equation methods for simulation of GFP kinetics in non–steady state experiments

2018 ◽  
Vol 29 (6) ◽  
pp. 763-771 ◽  
Author(s):  
Robert D. Phair
Keyword(s):  
Differential Equation ◽  
Steady State ◽  
Fluorescence Microscopy ◽  
Cell Biology ◽  
Fluorescent Proteins ◽  
Quantitative Information ◽  
Tracer Kinetics ◽  
Mathematical Framework ◽  
Experimental Protocols ◽  
Tracer Kinetic

Genetically encoded fluorescent proteins, combined with fluorescence microscopy, are widely used in cell biology to collect kinetic data on intracellular trafficking. Methods for extraction of quantitative information from these data are based on the mathematics of diffusion and tracer kinetics. Current methods, although useful and powerful, depend on the assumption that the cellular system being studied is in a steady state, that is, the assumption that all the molecular concentrations and fluxes are constant for the duration of the experiment. Here, we derive new tracer kinetic analytical methods for non–steady state biological systems by constructing mechanistic nonlinear differential equation models of the underlying cell biological processes and linking them to a separate set of differential equations governing the kinetics of the fluorescent tracer. Linking the two sets of equations is based on a new application of the fundamental tracer principle of indistinguishability and, unlike current methods, supports correct dependence of tracer kinetics on cellular dynamics. This approach thus provides a general mathematical framework for applications of GFP fluorescence microscopy (including photobleaching [FRAP, FLIP] and photoactivation to frequently encountered experimental protocols involving physiological or pharmacological perturbations (e.g., growth factors, neurotransmitters, acute knockouts, inhibitors, hormones, cytokines, and metabolites) that initiate mechanistically informative intracellular transients. When a new steady state is achieved, these methods automatically reduce to classical steady state tracer kinetic analysis.

scholarly journals Granulocytopoiesis. II. Emergence and Pattern of Labeling of Neutrophilic Granulocytes in Humans

Blood ◽  
1964 ◽  
Vol 24 (6) ◽  
pp. 683-700 ◽  
Author(s):  
T. M. FLIEDNER ◽  
E. P. CRONKITE ◽  
S. Å. KILLMANN ◽  
V. P. BOND
Keyword(s):  
Steady State ◽  
Peripheral Blood ◽  
Bacterial Infections ◽  
Neutrophilic Granulocytes ◽  
Constant Input ◽  
State Equilibrium ◽  
Nuclear Maturation ◽  
Myelocytic Leukemia ◽  
Sample Interval ◽  
Cytoplasmic Maturation

Abstract 1. Following administration of H3-thymidine to 15 patients with a variety of hemopoietic conditions, the emergence and the pattern of labeling of neutrophilic granulocytes were studied in peripheral blood leukocytic concentrates. The hematologic diagnosis included five in which the hemopoiesis appeared to be in a steady state equilibrium at the time of study, three with various types of leukemia, one with lymphosarcoma, two with multiple myeloma, one with myelofibrosis, two with pernicious anemia (once before and once after therapy) and two with bacterial infections. 2. The emergence time of neutrophilic segmented granulocytes (time from H3-thymidine injection to the first appearance of labeled segmented forms in the peripheral blood) was found to vary in steady state equilibrium from 96 to 144 hours. It was shortened to 48 hours in two instances with bacterial infection. This was interpreted as indicating a faster than normal nuclear maturation with normal or delayed cytoplasmic maturation (dissociation in nuclear and cytoplasmic maturation). 3. The number of segments of neutrophilic granulocytes was found to be unrelated to cell age as had been hypothesized by Arneth many years ago. However, bandforms were found in the circulation about 24 hours earlier than segmented forms, suggesting that they are younger and that some are acceptable to the blood while others continue to mature to segmented forms. Pelgeroid cells with round or bilobed nuclei found in one case of subleukemic myelocytic leukemia were found to emerge simultaneously 132 hours after H3-thymidine injection. This suggests that both types are identical in their degree of maturation. Thus the cells with round nuclei are not band forms but result possibly from a delayed nuclear maturation. 4. In patients studied for at least 2 weeks, characteristic undulations of the labeling indices of the segmented granulocytes were found. If the sampling intervals were 24 hours, peaks were found 6 days apart, the second peak being about half of the labeling index of the first. If the sample interval was shorter, a finer structure was observed with undulations showing peak intervals of 2-3 days. Although the significance is obscure at present, the constancy of the findings suggest that there may be a constant input of cells with the index of labeling varying due to some synchrony of the precursor population(s). Alternative explanations are discussed.

Post-transcriptional regulation of bovine parathyroid hormone synthesis

1993 ◽  
Vol 10 (1) ◽  
pp. 43-49 ◽  
Author(s):  
N S Hawa ◽  
J L H O'Riordan ◽  
S M Farrow
Keyword(s):  
Transcriptional Regulation ◽  
Steady State ◽  
Actinomycin D ◽  
Mrna Levels ◽  
Dot Blot ◽  
Hormone Synthesis ◽  
Membrane Bound ◽  
Post Transcriptional Regulation ◽  
Bovine Parathyroid Hormone ◽  
In Cells

ABSTRACT Incubation of bovine parathyroid cells for 48 h in 0·4 mmol calcium/l had no significant effect on steady-state preproparathyroid hormone (preproPTH) mRNA levels when compared with cells incubated in 1·0 mmol calcium/l, but low calcium concentrations increased the membrane-bound polysomal content of preproPTH mRNA by 200±16% (mean±s.d.). No preproPTH mRNA was detected on free polysomes. Actinomycin D (5 and 10 μg/ml) had no effect on steady-state preproPTH mRNA levels measured in dot-blot assays after 24 h, but reduced levels in cells incubated in 1·0 mmol calcium/l to 54±16% and 39±12% of control values respectively after 48 h of incubation. Similarly, in cells incubated in 0·4 mmol calcium/l, actinomycin D (5 and 10μg/ml) reduced steady-state preproPTH mRNA levels to 57±13% and 45±5% of control values respectively. Actinomycin D did not prevent the rise in polysomal content of preproPTH mRNA induced in cells by incubation in 0·4 mmol calcium/l, but increased polysomal content in cells incubated in 0·4 and 1·0mmol calcium/l by 159±9% and 164±13% respectively after 48 h. These results demonstrate post-transcriptional regulation of PTH synthesis in cultured bovine parathyroid cells, and suggest that this control involves a protein which may be calcium-sensitive.

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