SEARCH · PubMed Health

Results for “Gene Expression Regulation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed1995

Tetracycline-regulated gene expression following direct gene transfer into mouse skeletal muscle.

For most experimental and therapeutic applications of gene transfer, regulation of the timing and level of gene expression is preferable to constitutive gene expression. Among the systems that have been developed for pharmacologically controlled gene expression in mammalian cells, the bacterial tetracycline (tet)-responsive system has the advantage that it is dependent on a drug (tet) that is both highly specific and non-toxic. The tet-responsive system has been previously used to modulate expression of cell cycle regulatory proteins in cultured cells, reporter genes in plants and transgenic mice and reporter genes directly injected into the heart. Here we show that orally or parenterally administered tet regulates expression of tet-responsive plasmids injected directly into mouse skeletal muscle. Reporter gene expression was suppressed by two orders of magnitude in the presence of tet, and that suppression was reversed when tet was withdrawn. These data show that skeletal muscle offers an accessible and well characterized target tissue for tet-controlled expression of genes in vivo, suggesting applications to developmental studies and gene therapy.

Animals↗

PubMed2000

Adenovirus-mediated transfer of regulable gene expression.

The past several years have seen significant progress in the development of adenoviral vectors with markedly decreased pathological potential and greatly increased capacity for incorporation of foreign DNA. Paralleling these developments in gene transfer technology have been remarkable advances in both the design and optimization of gene regulatory systems. Ultimately, the goal of these gene regulatory systems is control of transgene expression in vivo by the administration of an exogenous compound. With the prospect of clinical human gene therapy on the horizon, the co-evolution of safe and efficient gene transfer strategies, with effective regulation of transgene expression, represents an essential step towards therapeutically viable gene transfer protocols. This review introduces recent advances in both adenoviral-based vectors and gene regulatory systems, and examines those studies in which adenoviral vectors and gene-regulatory systems have been combined in vivo.

Adenoviridae↗

PubMed2003

Design principles for regulator gene expression in a repressible gene circuit.

We consider the design of a type of repressible gene circuit that is common in bacteria. In this type of circuit, a regulator protein acts to coordinately repress the expression of effector genes when a signal molecule with which it interacts is present. The regulator protein can also independently influence the expression of its own gene, such that regulator gene expression is repressible (like effector genes), constitutive, or inducible. Thus, a signal-directed change in the activity of the regulator protein can result in one of three patterns of coupled regulator and effector gene expression: direct coupling, in which regulator and effector gene expression change in the same direction; uncoupling, in which regulator gene expression remains constant while effector gene expression changes; or inverse coupling, in which regulator and effector gene expression change in opposite directions. We have investigated the functional consequences of each form of coupling using a mathematical model to compare alternative circuits on the basis of engineering-inspired criteria for functional effectiveness. The results depend on whether the regulator protein acts as a repressor or activator of transcription at the promoters of effector genes. In the case of repressor control of effector gene expression, direct coupling is optimal among the three forms of coupling, whereas in the case of activator control, inverse coupling is optimal. Results also depend on the sensitivity of effector gene expression to changes in the level of a signal molecule; the optimal form of coupling can be physically realized only for circuits with sufficiently small sensitivity. These theoretical results provide a rationale for autoregulation of regulator genes in repressible gene circuits and lead to testable predictions, which we have compared with data available in the literature and electronic databases.

Gene Expression Regulation, Bacterial↗

PubMed2001

Adaptable doxycycline-regulated gene expression systems for Drosophila.

We have engineered two new versions of the doxycycline (dox) inducible system for use in Drosophila. In the first system, we have used the ubiquitously expressed Drosophila actin5C promoter to express the Tet-Off transactivator (tTA) in all tissue. Induction of a luciferase target transgene begins 6 h after placing the flies on dox-free food. Feeding drug-free food to mothers results in universal target gene expression in their embryos. Larvae raised on regular food also show robust expression of a target reporter gene. In the second version, we have used the Gal4-UAS system to spatially limit expression of the transactivator. Dox withdrawal results in temporally- and spatially-restricted, inducible expression of luciferase in the adult head and embryo. Both the actin5C and Gal4-UAS versions produce more than 100-fold induction of luciferase in the adult, with virtually no leaky expression in the presence of drug. Reporter gene expression is also undetectable in larvae or embryos from mothers fed dox-containing food. Such tight control may be due to the incorporation of Drosophila insulator elements (SCS and SCS') into the transgenic vectors. These systems offer a practical, effective alternative to currently available expression systems in the Drosophila research community.

Actins↗

PubMed1990

Complex character of senS, a novel gene regulating expression of extracellular-protein genes of Bacillus subtilis.

The senS gene of Bacillus subtilis, which in high copy number stimulates the expression of several extracellular-protein genes, has been cloned, genetically mapped, and sequenced. The gene codes for a highly charged basic protein containing 65 amino acid residues. The gene is characterized by the presence of a transcription terminator (attenuator) located between the promoter and open reading frame, a strong ribosome-binding site, and a strong transcription terminator at the 3' end of this monocistronic gene. The amino acid sequence of SenS showed partial homology with the N-terminal core binding domain region of bacterial RNA polymerase sigma factors and a helix-turn-helix motif found in DNA-binding proteins. The gene can be deleted without any effect on growth or sporulation.

Amino Acid Sequence↗

PubMed2003

[Evaluation of targets for antifungal drugs using a system to regulate gene expression].

A system to regulate gene expression is a convenient tool to explore gene function(s) not only in prokaryote but also in eukaryote. Such manipulation tools are scarce in the medical mycology field due to its complexity and diploidity. Although systems to regulate gene expression have been constructed, most of them are restricted in their application to particular culture conditions due to the nature of the promoter used. This motivated us to establish a new regulatable expression system that can function regardless of culture conditions, including in a host. In this review, a new system using tetracycline or its derivative as a molecular switch is introduced, which can function in several culture conditions, and in a host. We also show that the system can be applied to the selection of antifungal drug targets, which is the first step in a target-based strategy for drug discovery.

Anti-Bacterial Agents↗

PubMed1999

Std1 and Mth1 proteins interact with the glucose sensors to control glucose-regulated gene expression in Saccharomyces cerevisiae.

The Std1 protein modulates the expression of glucose-regulated genes, but its exact molecular role in this process is unclear. A two-hybrid screen for Std1-interacting proteins identified the hydrophilic C-terminal domains of the glucose sensors, Snf3 and Rgt2. The homologue of Std1, Mth1, behaves differently from Std1 in this assay by interacting with Snf3 but not Rgt2. Genetic interactions between STD1, MTH1, SNF3, and RGT2 suggest that the glucose signaling is mediated, at least in part, through interactions of the products of these four genes. Mutations in MTH1 can suppress the raffinose growth defect of a snf3 mutant as well as the glucose fermentation defect present in cells lacking both glucose sensors (snf3 rgt2). Genetic suppression by mutations in MTH1 is likely to be due to the increased and unregulated expression of hexose transporter genes. In media lacking glucose or with low levels of glucose, the hexose transporter genes are subject to repression by a mechanism that requires the Std1 and Mth1 proteins. An additional mechanism for glucose sensing must exist since a strain lacking all four genes (snf3 rgt2 std1 mth1) is still able to regulate SUC2 gene expression in response to changes in glucose concentration. Finally, studies with green fluorescent protein fusions indicate that Std1 is localized to the cell periphery and the cell nucleus, supporting the idea that it may transduce signals from the plasma membrane to the nucleus.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Amino acid regulation of gene expression.

Regulation of gene expression by amino acids is mediated through a number of mechanisms affecting both the transcription of DNA and the translation of mRNA. This report reviews recent findings demonstrating a role for amino acids in regulating the initiation phase of mRNA translation. The report focuses on key regulatory events in translation initiation and discusses some of the signaling pathways through which amino acid sufficiency or the lack thereof is communicated within the cell. It concludes with a consideration of some of the important unanswered questions in this rapidly advancing area of research.

Adaptor Proteins, Signal Transducing↗

PubMed1989

Expression and organization of BP74, a cyclic AMP-regulated gene expressed during Dictyostelium discoideum development.

We have characterized a cDNA and the corresponding gene for a cyclic AMP-inducible gene expressed during Dictyostelium development. This gene, BP74, was found to be first expressed about the time of aggregate formation, approximately 6 h after starvation. Accumulation of BP74 mRNA did not occur in Dictyostelium cells that had been starved in fast-shaken suspension cultures but was induced in similar cultures to which cyclic AMP pulses had been added. The BP74 cDNA and gene were characterized by DNA sequence analysis and transcriptional mapping. When the BP74 promoter region was fused with a chloramphenicol acetyltransferase reporter gene and reintroduced into Dictyostelium cells, the transfected chloramphenicol acetyltransferase gene displayed the same developmentally regulated pattern of expression as did the endogenous BP74 gene, suggesting that all of the cis-acting elements required for regulated expression were carried by a 2-kilobase cloned genomic fragment. On the basis of sequence analysis, the gene appeared to encode a protein containing a 20-residue hydrophobic sequence at the amino-terminal end and 26 copies of a 20-amino-acid repeat.

Amino Acid Sequence↗

PubMed1991

Cold acclimation and cold-regulated gene expression in ABA mutants of Arabidopsis thaliana.

We have examined the cold-induced enhancement of freezing tolerance and expression of cold-regulated (cor) genes in Arabidopsis thaliana (L.) Heynh (Landsberg 'erecta') and abscisic acid (ABA)-deficient (aba) and ABA-insensitive (abi) mutants derived from it. The results indicate that the abi mutations had no apparent effect on freezing tolerance, while the aba mutations did: cold-acclimated aba mutants were markedly impaired in freezing tolerance compared to wild-type plants. In addition, it was observed that non-frozen leaves from both control and cold-treated aba mutant plants were more ion-leaky than those from corresponding wild-type plants. These data are consistent with previous observations indicating that ABA levels can affect freezing tolerance. Whether ABA has a direct role in the enhancement of freezing tolerance that occurs during cold acclimation, however, is uncertain. Several studies have suggested that ABA might mediate certain changes in gene expression that occur during cold acclimation. Our data indicate that the ABA-induced expression of three ABA-regulated Arabidopsis cor genes was unaffected in the abi2, abi3, and aba-1 mutants, but was dramatically impaired in the abi1 mutant. Cold-regulated expression of all three cor genes, however, was nearly the same in wild-type and abi1 mutant plants. These data suggest that the cold-regulated and ABA-regulated expression of the three cor genes may be mediated through independent control mechanisms.

Abscisic Acid↗

PubMed1997

Versatile retrovirus vector systems for regulated gene expression in vitro and in vivo.

BACKGROUND: Several plasmid DNA-based mammalian expression systems have recently been developed which make it possible to manipulate gene expression via the administration of exogenous agents. In order to extend the application of these systems, we have developed retroviral vectors which allow for the controlled expression of inserted genes both in vitro and in vivo. MATERIALS AND METHODS: Two vector strategies which make use of the tetracycline-regulated gene expression system described by Gossen and Bujard were evaluated. In a first strategy, one virus was generated which encoded the tTA or rtTA transactivator gene product, and a second virus was generated in which expression of the gene of interest was dependent upon tetracycline-responsive transcriptional control elements placed either within the viral LTR or within the proviral transcriptional unit. In a second vector strategy, both components of the tet-regulatable system were incorporated into a single proviral genome in such a way that expression of both the transgene and the transactivator gene product were under control of tet-regulatable control elements. RESULTS: Both vector strategies resulted in the ability to regulate the expression of inserted genes. In one single virus configuration, gene expression could be regulated over 100X and the level of gene expression in the induced state was comparable to or greater than that achieved with standard LTR-based vectors. The use of different deletions in the viral LTR made it possible to generate a number of vectors which provide for a four-fold range of levels of expression of inserted genes in the induced state. Studies in mice with transduced cells demonstrated that gene expression could be induced in vivo by manipulation of tetracycline for at least 48 days. CONCLUSIONS: The availability of highly transmissible, regulatable retroviral vectors should greatly facilitate studies in which it is of interest to manipulate the expression of specific genes in vitro or in vivo.

3T3 Cells↗

PubMed2003

Changes in peroxisome proliferator-activated receptor gamma-regulated gene expression and inhibin/activin-follistatin system gene expression in rat testis after an administration of di-n-butyl phthalate.

Changes in gene expression regulated by peroxisome proliferator-activated receptor gamma (PPARgamma) and in gene expression related to the inhibin/activin-follistatin system in the rat testis induced by a single oral administration of di-n-butyl phthalate (DBP) (8.6 mmol/kg) were examined and compared with those in the control rats using reverse-transcriptase polymerase chain reaction (RT-PCR). The increase in cytochrome P450 4A1 mRNA, which is regulated by PPARalpha, was significant, but not so profound as the increase of P450 4A1 mRNA in the liver. In contrast, a remarkable increase in the mRNA level of plasminogen activator inhibitor-1 (PAI-1) was found in the testis, suggesting the activation of PPARgamma. The substantial increase in PAI-1 may be related to the disruption of spermatogenesis. On the other hand, significant suppression of the mRNA level of inhibin beta(B) and elevation in the mRNA level of follistatin, an activin-binding protein, were observed after the DBP-administration. Activin B, a homodimer of inhibin beta(B), is known to stimulate spermatogonial proliferation. The present results suggest that the suppression of spermatogenesis resulting from the changes in the expression of genes involved in the inhibin/activin-follistatin system is one of the mechanisms of the testicular atrophy induced by DBP.

Animals↗

PubMed2001

Insulin-regulated gene expression.

Insulin regulates the expression of more than 150 genes, indicating that this is a major action of this hormone. At least eight distinct consensus insulin response sequence (IRSs) have been defined through which insulin can regulate gene transcription. These include the serum response element, the activator protein 1 ('AP-1') motif, the Ets motif, the E-box motif and the thyroid transcription factor 2 ('TTF-2') motif. All of these IRSs mediate stimulatory effects of insulin on gene transcription. In contrast, an element with the consensus sequence T(G/A)TTT(T/G)(G/T), which we refer to as the phosphoenolpyruvate carboxykinase (PEPCK)-like motif, mediates the inhibitory effect of insulin on transcription of the genes encoding PEPCK, insulin-like-growth-factor-binding protein 1 (IGFBP-1), tyrosine aminotransferase and the glucose-6-phosphatase (G6Pase) catalytic subunit. The forkhead transcription factor FKHR has recently been shown to bind this PEPCK-like IRS motif and a model has been proposed in which insulin inhibits gene transcription by stimulating the phosphorylation and nuclear export of FKHR. Our results suggest that this model is consistent with the action of insulin on transcription of the gene encoding IGFBP-1 but not that of the G6Pase catalytic subunit. Thus, even though the IRSs in both promoters seem identical, they are functionally distinct. In addition, in the G6Pase catalytic subunit promoter, hepatocyte nuclear factor 1 ('HNF-1'), acts as an accessory factor to enhance the effect of insulin mediated through the IRS.

Animals↗

PubMed2000

Complex roles of Stat1 in regulating gene expression.

Stat1 is a fascinating and complex protein with multiple, yet contrasting transcriptional functions. Upon activation, it drives the expression of many genes but also suppresses the transcription of others. These opposing characteristics also apply to its role in facilitating crosstalk between signal transduction pathways, as it participates in both synergistic activation and inhibition of gene expression. Stat1 is a functional transcription factor even in the absence of inducer-mediated activation, participating in the constitutive expression of some genes. This review summarizes the well studied involvement of Stat1 in IFN-dependent and growth factor-dependent signaling and then describes the roles of Stat1 in positive, negative and constitutive regulation of gene expression as well as its participation in crosstalk between signal transduction pathways. Oncogene (2000).

Animals↗

PubMed2004

Bacterial expression system with tightly regulated gene expression and plasmid copy number.

A new Escherichia coli host/vector system has been engineered to allow tight and uniform modulation of gene expression and gamma origin (ori) plasmid copy number. Regulation of gamma ori plasmid copy number is achieved through arabinose-inducible expression of the necessary Rep protein, pi, whose gene was integrated into the chromosome of the host strain under control of the P(BAD) promoter. gamma ori replication can be uniformly modulated over 100-fold by changing the concentration of l-arabinose in the growth medium. This strain avoids the problem of all-or-nothing induction of P(BAD) because it is deficient in both arabinose uptake and degradation genes. Arabinose enters the cell by a mutant LacY transporter, LacYA177C, which is expressed from the host chromosome. Although this strain could be compatible with any gamma ori plasmid, we describe the utility of a gamma ori expression vector that allows especially tight regulation of gene expression. With this host/vector system, it is possible to independently modulate gene expression and gene dosage, facilitating the cloning and overproduction of toxic gene products. We describe the successful use of this system for cloning a highly potent toxin, Colicin E3, in the absence of its cognate immunity protein. This system could be useful for cloning genes encoding other potent toxins, screening libraries for potential toxins, and maintaining any gamma ori vector at precise copy levels in a cell.

Adenosine Triphosphatases↗

PubMed1988

Transmembrane signal transduction regulates gene expression in Dictyostelium discoideum.

cAMP regulates gene expression in Dictyostelium discoideum through the cell surface receptor and is therefore a transmembrane signal transduction event. We have now begun to examine the signal transduction pathway that transmits the cAMP-induced signal to the nucleus. The results presented here indicate that Ca2+ plays a crucial role. A comparison of the accumulation of UDPGP1 mRNA during development with the corresponding transcription rates revealed that this gene is regulated primarily at the level of transcription. To elucidate the factors involved in the regulation of the UDPGP1 gene we characterized its cis acting sequences. We constructed a series of deletions into the 5' flanking region of the UDPGP1 gene and analyzed the expression of the mutated DNA in transformants. A sequence element essential for the expression of the UDPGP1 gene is located between -500 bp and -288 bp from the transcription start site. This promoter element appears to be a short G + C-rich sequence positioned between -374 to -395 and coincides with a DNase I hypersensitive site.

Base Sequence↗

PubMed2001

Tetracycline regulated gene expression in Leishmania donovani.

The prokaryotic tetracycline-responsive repressor/operator system has proven to be useful for studying the function of essential genes and the expression of toxic gene products in a number of organisms, including Trypanosoma brucei. We report here the adaptation of this system for use in Leishmania. The inducible promoter construct contains a bleomycin resistance-luciferase fusion (BLE-LUC) gene driven by an rRNA promoter with two copies of the TetO sequence inserted two nucleotides upstream of the transcriptional start site. This construct showed regulation of BLE-LUC expression by two orders of magnitude when targeted into the rDNA locus in the reverse orientation relative to transcription of the rRNA genes in a Leishmania donovani cell line expressing TETR. The luciferase expression level in the absence of tetracycline was approximately 50-fold lower than that in the tubulin locus (where it is transcribed by pol II), while the expression level in the presence of tetracycline was approximately five-fold higher than that from the tubulin locus. There was no linear relationship between the level of TETR expression and the regulation, and changing of positions of operator did not increase regulation.

Animals↗

PubMed1992

ming is expressed in neuroblast sublineages and regulates gene expression in the Drosophila central nervous system.

Cell diversity in the Drosophila central nervous system (CNS) is primarily generated by the invariant lineage of neural precursors called neuroblasts. We used an enhancer trap screen to identify the ming gene, which is transiently expressed in a subset of neuroblasts at reproducible points in their cell lineage (i.e. in neuroblast 'sublineages'), suggesting that neuroblast identity can be altered during its cell lineage. ming encodes a predicted zinc finger protein and loss of ming function results in precise alterations in CNS gene expression, defects in axonogenesis and embryonic lethality. We propose that ming controls cell fate within neuroblast cell lineages.

Amino Acid Sequence↗