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At least 541 records · Page 30Linked to original sources
PubMed1988

Signals important for high-level expression of foreign genes in Autographa californica nuclear polyhedrosis virus expression vectors.

The transcriptional and translational signals required for efficient expression of the chloramphenicol acetyltransferase, beta-galactosidase, and tissue plasminogen activator genes, under the control of the polyhedrin promoter in Spodoptera frugiperda cells infected with Autographa californica nuclear polyhedrosis virus, were investigated by SDS-PAGE and RNA dot blot analysis. The recombinant baculoviruses all contained alterations in the leader sequence or 5' proximal coding region of the polyhedrin gene. Highest levels of foreign proteins and polyhedrin-linked mRNAs were observed when portions of the coding sequence of the polyhedrin gene were fused in phase with the foreign gene. Recombinant viruses in which the foreign gene was inserted upstream from the polyhedrin ATG start codon expressed nonfused products but at lower levels than contructs which produced fusion proteins. A corresponding decrease in the levels of mRNAs produced by such constructs was also observed. Some constructs in which the foreign gene was inserted out of phase downstream from the polyhedrin start codon expressed nonfused protein products at low levels but produced polyhedrin-linked mRNA at levels comparable to vectors which produced protein fusions. These data suggest that reinitiation of translation can take place at AUG start codons a short distance downstream from the primary polyhedrin start codon. These results indicate that sequences immediately upstream from the polyhedrin start codon are important for regulation of transcription and that additional sequences near the AUG start codon can have a dramatic influence on the levels of translation observed.

Animals↗
PubMed2002

Karyopherin alpha2: a control step of glucose-sensitive gene expression in hepatic cells.

Glucose is required for an efficient expression of the glucose transporter GLUT2 and other genes. We have shown previously that the intracytoplasmic loop of GLUT2 can divert a signal, resulting in the stimulation of glucose-sensitive gene transcription. In the present study, by interaction with the GLUT2 loop, we have cloned the rat karyopherin alpha2, a receptor involved in nuclear import. The specificity of the binding was restricted to GLUT2, and not GLUT1 or GLUT4, and to karyopherin alpha2, not alpha1. When rendered irreversible by a cross-linking agent, this transitory interaction was detected in vivo in hepatocytes. A role for karyopherin alpha2 in the transcription of two glucose-sensitive genes was investigated by transfection of native and inactive green fluorescent protein-karyopherin alpha2 in GLUT2-expressing hepatoma cells. The amount of inactive karyopherin alpha2 receptor reduced, in a dose-dependent manner, the GLUT2 and liver pyruvate kinase mRNA levels by competition with endogenous active receptor. In contrast, the overexpression of karyopherin alpha2 did not significantly stimulate GLUT2 and liver pyruvate kinase mRNA accumulation in green fluorescent protein-sorted cells. The present study suggests that, in concert with glucose metabolism, karyopherin alpha2 transmits a signal to the nucleus to regulate glucose-sensitive gene expression. The transitory tethering of karyopherin alpha2 to GLUT2 at the plasma membrane might indicate that the receptor can load the cargo to be imported locally.

Animals↗
PubMed2001

Cloning and high expression of catalase gene from bacillus sp. TE124.

An efficient expression system for producing catalase in Bacillus was developed. A catalase was purified from Bacillus sp. TE124 and the catalase gene was cloned by plaque hybridization with a probe constructed from the N-terminal amino acid sequence of the enzyme. The gene, containing an open reading frame of 1452 bp, was subcloned into pHY300PLK for self-cloning into the organism. As a result, the production of catalase increased 20-fold over that of the parent strain.

Journal Article↗
PubMed1991

Influence of yeast proteases on hirudin expression in Saccharomyces cerevisiae.

Recombinant desulfatohirudin variant 1 is efficiently expressed and secreted from Saccharomyces cerevisiae. Chemical analysis of the secreted hirudin compounds revealed the presence of the full-length hirudin molecule as well as two degradation products that lack the C-terminal and in addition the penultimate amino acid, respectively. To eliminate the yeast proteases possibly involved in C-terminal hirudin proteolysis, we disrupted either the structural gene for endoprotease yscA (PRA1) or the gene encoding carboxypeptidase yscY (PRC1). Both isogenic mutant strains secreted significantly higher amounts of full-length hirudin as compared to the parental strain. This suggests an involvement of carboxypeptidase yscY in hirudin proteolysis, since both protease disruptions lead to a lack in yscY activity; a yscA mutant accumulates the inactive yscY precursor. However, the strain devoid of protease yscA yielded significantly lower titers of total hirudin than the strain lacking yscY, but containing yscA.

Animals↗
PubMed2002

Selective expression of immunogenic, virus-like particle-derived antibody-binding epitopes.

The incorporation of linear and conformational antibody-binding epitopes into polyepitope, chimeric antigens with satisfactory immunogenicity is a challenge. We selectively expressed antigen fragments encoding the linear e2 epitope (C(79-149)) of hepatitis B virus (pre)core antigen (HBc/eAg) and the conformational 'a' epitope (S(80-180)) of hepatitis B surface antigen (HBsAg) in a novel system. The domains were expressed as chimeric antigens containing either heat shock protein (hsp)73-binding simian virus 40 large tumor antigen (e.g. T(77)) or non-hsp-binding (e.g. T(60)) sequences at their N-termini. We compared their type of expression with their immunogenicity for B cells (when delivered as a DNA vaccine). The type of expression investigated included their level of expression, the secretion or intracellular expression of the antigen and the stress protein (hsp)-associated versus nonassociated expression. The linear e2 epitope of HBc/eAg was efficiently expressed as an intracellular, hsp73-binding fusion protein, and efficiently primed an HBc/eAg-specific antibody response when delivered in this form. The conformational 'a' epitope of HBsAg most efficiently stimulated B cells as a secreted, non-hsp-associated fusion protein. These data demonstrate that different B cell-stimulating epitopes of vaccine-relevant viral antigens can be selectively isolated and expressed in suitable expression systems, but that the requirements that have to be fulfilled to obtain optimal immunogenicity differ strikingly between individual epitopes.

Animals↗
PubMed1987

Cloning and characterization of the 5' region of the cell wall protein gene operon in Bacillus brevis 47.

Bacillus brevis 47 secretes vast amounts of proteins derived from both middle wall protein (MWP) and outer wall protein into the medium. The 5' region of the cell wall protein gene operon was cloned into Bacillus subtilis and subsequently into B. brevis 47. On the basis of the nucleotide sequence analysis, an open reading frame coding for MWP was identified on the cloned DNA fragment. Two potential translation initiation sites for the MWP gene are located tandemly in the same reading frame. Each of the sites contains a sequence highly homologous to the 3' end of B. brevis rRNA and an initiation codon. The translational fusion of the 5' region of the MWP gene with the Bacillus licheniformis alpha-amylase gene resulted in the efficient expression of the alpha-amylase gene in B. brevis 47. Of the two potential translation initiation sites, the one located upstream could be eliminated without affecting the expression of the MWP-alpha-amylase fusion gene, suggesting that MWP is synthesized in a precursor form with a signal peptide of 23 amino acid residues. S1 nuclease mapping of the cell wall protein gene transcripts suggested the possibility of the existence of several promoters in the 5' region within 300 base pairs from the translation initiation sites; one promoter was definitely localized within this part of the 5' region, and it was capable of expressing a heterologous gene fusion at a high level. The roles of the apparent structural complexity of the 5' region of the cell wall protein gene operon are discussed in connection with the efficient gene expression.

Amino Acid Sequence↗
PubMed1995

Unique expression of major histocompatibility complex class I proteins in the absence of glucose trimming and calnexin association.

Recent evidence indicates that efficient expression of major histocompatibility complex (MHC) complexes requires their interaction with the resident endoplasmic reticulum (ER) chaperone calnexin, which for certain proteins functions as a lectin specific for monoglucosylated glycans. In the current report, we studied the expression of MHC class I proteins in BW wild type thymoma cells (BW WT) and glucosidase II-deficient BW PHAR2.7 cells. Consistent with a requirement for glucose (Glc) trimming for interaction of class I proteins with calnexin, we found that nascent H-2Kk proteins associated with calnexin in untreated BW WT cells, but not in BW WT cells treated with the glucosidase inhibitor castanospermine (cas), or in untreated glucosidase II-deficient BW PHAR2.7 cells. Surprisingly, we found that H-2Kk expression occurred with similar efficiency in BW PHAR2.7 cells as in BW WT cells and that formation of nascent H-2Kk complexes was perturbed by cas treatment in BW WT cells but not in BW PHAR2.7 cells. Finally, it was noted that expression of the molecular chaperone Bip was markedly increased in BW PHAR2.7 cells relative to BW WT cells, which is suggested to play a role in regulating the expression of H-2Kk complexes in BW PHAR2.7 cells. The current study demonstrates that Glc trimming is required for efficient interaction of nascent H-2Kk proteins with calnexin; that expression of MHC class I proteins can, under certain conditions, proceed effectively in the absence of Glc trimming and calnexin association; and that Bip expression is markedly increased under conditions where diglucosylated glycans persist on nascent glycoproteins within the ER. These data are consistent with the hypothesis that alternative oligomerization pathways exist for class I proteins within the quality control system of the ER that have differential requirements for removal of Glc residues from nascent glycan chains.

Biological Transport↗
PubMed1988

A high-efficiency vector for expression of foreign genes in myeloma cells.

We have constructed a high-efficiency vector for expression of genes of interest in myeloma cells. This vector is comprised of regulatory sequences from immunoglobulin (Ig) genes, including the heavy-chain enhancer, a kappa light-chain promoter and splice site, and the polyadenylation signal downstream from the kappa constant region. The expression capacity of this vector was assayed in J558L myeloma cells using human tissue plasminogen activator as a reporter gene. Stable transfectants were analyzed for protein, RNA, DNA copy number and transcription rate. Expression was compared to that of intact, transfected Ig genes and to endogenous Ig. Tissue plasminogen activator cloned into this vector was found to be expressed as efficiently as intact, transfected Ig genes, producing 1-2% of total cellular mRNA from a single copy of the gene. RNA levels and transcription rates relative to those of endogenous Ig genes were found to be about 25% and 38%, respectively. Because of its high efficiency, potential for gene amplification, and various scale-up advantages of myeloma cells, this vector-host system may yield levels of desired proteins than currently available systems.

Animals↗
PubMed1998

High-level expression of soluble heterologous proteins in the cytoplasm of Escherichia coli by fusion to the bacteriophage lambda head protein D.

The bacteriophage Lambda head protein D (gpD) is a small major capsid protein (110aa; 11.6kDa; pI=5.68, devoid of cysteine residues) that is essential for stable head morphogenesis. We found that a His-tagged derivative of gpD (gpHD) is a monomeric protein with efficient expression properties and high resistance towards thermally induced irreversible aggregation. In addition, gpHD can be used as a fusion partner for high-level expression of soluble heterologous proteins in the cytoplasm of Escherichia coli. Its broad utility is illustrated by the production of various mammalian proteins by fusion to its C-terminus. As a fusion partner, gpHD is thought to mediate optimal translation initiation while reducing inclusion body formation and protein degradation. In addition, it provides a His-tag for simple purification. gpHD may act as a 'cytoplasmic anchor' by keeping its unfolded fusion partner in solution, thereby providing more time for proper folding. An ever-increasing number of open reading frames (ORFs) are being identified in the various genome sequencing programs. gpHD has the potential to be harnessed for the development of highly efficient cytoplasmic expression systems that might contribute to the production and characterization of these novel polypeptides. Protein D is also an established fusion partner for phage display. It thus presents the attractive opportunity of coupling the selection of heterologous proteins from a phage library to their subsequent high-level expression.

Bacteriophage lambda↗
PubMed1999

PhaF, a polyhydroxyalkanoate-granule-associated protein of Pseudomonas oleovorans GPo1 involved in the regulatory expression system for pha genes.

The phaC1 gene codes for the medium-chain-length polyhydroxyalkanoate (mcl PHA) synthase of Pseudomonas oleovorans GPo1, which produces mcl PHA when grown in an excess of carbon source and under nitrogen limitation. In this work, we have demonstrated, by constructing a recombinant P. oleovorans strain carrying a phaC1::lacZ reporter system, that the phaC1 gene is expressed efficiently in the presence of octanoic acid while its expression is repressed when glucose or citrate is used as the carbon source. Moreover, a P. oleovorans GPo1 mutant (strain GPG-Tc6) expressing higher levels of the reporter gene than the wild-type strain in the presence of glucose or citrate has been generated by mini-Tn5 insertional mutagenesis. Characterization of this mutant allowed us to conclude that phaF, a gene located downstream of the pha gene cluster, was knocked out in this strain. P. oleovorans GPG-Tc6 regained the ability to control phaC1 gene expression when complemented with the phaF wild-type gene. Sequencing data revealed the presence of three complete open reading frames (ORFs) in this region: ORF1 and phaI and phaF genes. The amino acid sequences of the phaI gene product and the N-terminal half of the PhaF protein showed a significant degree of similarity. Furthermore, the primary structure of the PhaF C terminus identifies this protein as a member of the histone H1-like group of proteins. Northern blot analysis showed two transcription units containing phaF, i.e., phaF and phaIF transcripts. Expression of the phaIF operon is more efficient in the presence of octanoic acid and is enhanced by the lack of the PhaF protein. In addition, it has also been demonstrated that both PhaF and PhaI proteins are bound to PHA granules produced by P. oleovorans. A model for the role of PhaF in regulating PHA synthesis is presented.

Acyltransferases↗
PubMed1994

Rev of human immunodeficiency virus and Rex of the human T-cell leukemia virus type I can counteract an mRNA downregulatory element of the transferrin receptor mRNA.

Expression of the structural proteins of the human immunodeficiency virus type 1 (HIV-1), the human T-cell leukemia virus type I (HTLV-I), and of the transferrin receptor (TfR) mRNA depends on posttranscriptional regulatory mechanisms involving both positive and negative elements. In these systems the presence of elements decreasing mRNA expression have been demonstrated. The regulatory proteins (Rev, Rex or iron response element binding protein IRE-BP) antagonize the effects of the downregulatory elements by interacting directly with specific mRNA sites (Rev responsive element, RRE, Rex responsive element, RXRE, or iron responsive elements, IREs) resulting in stabilization and efficient expression of the corresponding mRNAs. To investigate whether this strategy involves common pathways of mRNA utilization, we have studied expression from hybrid mRNAs that contained these previously identified HIV-1 or TfR instability determinants and the binding sites of the regulatory proteins Rev, Rex and/or IRE-BP. Our results demonstrate that only low levels of these hybrid mRNAs accumulate in the absence of the positive regulatory factors Rev, Rex or IRE-BP. The presence of these factors counteracts the effect of heterologous downregulatory elements resulting in increased accumulation of the hybrid mRNAs. However, while Rev or Rex regulation also resulted in efficient protein expression, the IRE-BP only affected mRNA levels without significantly affecting protein expression, suggesting that the pathways of mRNA stabilization/expression are different in these systems.

Deferoxamine↗
PubMed2004

Recombinant adenovirus administration in rat peritoneum: endothelial expression and safety concerns.

BACKGROUND: Initial studies of adenovirus-mediated gene transfer to the peritoneum have shown transgene expression in the mesothelium from the parietal peritoneum. Using a replication-deficient adenovirus encoding beta-galactosidase (Ad beta Gal), we investigated the expression efficiency and the distribution of the transgene to different areas of both visceral and parietal peritoneum and to extra-peritoneal tissues. METHODS: Male Wistar rats received an intraperitoneal injection of 15 ml of 0.9% NaCl alone or containing 1 x 10(9) or 3 x 10(9) p.f.u. of Ad beta Gal. Evaluations of the histology of the peritoneum, the transgene expression and the safety of adenovirus-mediated gene transfer, using measurement of both beta Gal activity and staining, were performed 1, 3 and 5 days post-injection. RESULTS: At 1 day post-injection of 3 x 10(9) p.f.u. of Ad beta Gal, significant beta Gal activity and staining were detected in the omentum and mesenteric peritoneum. beta Gal staining was observed in endothelial cells, mesothelial cells and adipocytes. Focal mononuclear infiltrates restricted to the submesothelial area of the visceral peritoneum were also observed. No expression was detected in the mesocolon and parietal peritoneum, where the mesothelium was damaged. Significant beta Gal activity and staining were observed in lymph nodes, lungs, liver, heart and kidneys, in the absence of inflammatory changes. CONCLUSIONS: Intraperitoneal delivery of adenoviral vectors allows highly efficient transgene expression in mesothelial cells, but also in endothelial cells and adipocytes of the visceral peritoneum. Adverse focal mononuclear infiltrates, as well as spreading of the adenoviral vector from the abdominal cavity to the systemic circulation, were observed in parallel. Transgene expression in endothelial cells is potentially important since the latter play a key role in the alterations of the peritoneal membrane associated with long-term peritoneal dialysis. However, these data emphasize the need for less immunogenic adenoviral vectors, ideally containing an endothelial cell-specific promoter, to overcome immune response-related problems and spreading to extra-peritoneal tissues.

Adenoviridae↗
PubMed2005

Pre-mRNA processing enhancer (PPE) elements from intronless genes play additional roles in mRNA biogenesis than do ones from intron-containing genes.

Most mRNA-encoding genes require introns for efficient expression in high eukaryotes. However, mRNAs can efficiently accumulate in the cytoplasm without intron excision if they contain cis-acting elements such as the post-transcriptional regulatory element (PRE) of hepatitis B virus (HBV), the constitutive transport element (CTE) of Mason-Pfizer monkey virus (MPMV), or the pre-mRNA processing enhancer (PPE) of herpes simplex virus' thymidine kinase (HSV-TK) gene. We compared the activities of these viral elements, the Rev-responsive element (RRE) of the human immunodeficiency virus (HIV), and the human c-Jun gene's enhancer (CJE), an element newly identified here, to enable expression of an intronless variant of the human beta-globin gene. The PRE, PPE and CJE from naturally intronless genes, but not the CTE or RRE from intron-containing genes, significantly enhanced stability, 3' end processing and cytoplasmic accumulation. When the transcripts included the beta-globin gene's first intron, the PRE, PPE and CJE still enhanced mRNA biogenesis, in some cases without intron excision. Thus, elements enabling stability, 3' end formation and nucleocytoplasmic export, not the presence of introns or their excision per se, are necessary for mRNA biogenesis. While the CTE and RRE primarily enhance nucleocytoplasmic export, PPE-like elements from naturally intronless genes facilitate polyadenylation as well.

Active Transport, Cell Nucleus↗
PubMed2005

Variant upstream regulatory region sequences differentially regulate human papillomavirus type 16 DNA replication throughout the viral life cycle.

While the central role of the viral upstream regulatory region (URR) in the human papillomavirus (HPV) life cycle has been well established, its effects on viral replication factor expression and plasmid replication of HPV type 16 (HPV16) remain unclear. Some nonprototypic variants of HPV16 contain altered URR sequences and are considered to increase the oncogenic risk of infections. To determine the relationship between viral replication and variant URRs, hybrid viral genomes were constructed with the replication-competent HPV16 prototype W12 and analyzed in assays which recapitulate the different phases of normal viral replication. The establishment efficiencies of hybrid HPV16 genomes differed about 20-fold among European prototypes and variants from Africa and America. Generally, European and African genomes exhibited the lowest replication efficiencies. The high replication levels observed with American variants were primarily attributable to their efficient expression of the replication factors E1 and E2. The maintenance levels of these viral genomes varied about fivefold, which correlated with their respective establishment phenotypes and published P(97) activities. Vegetative DNA amplification could also be observed with replicating HPV16 genomes. These results indicate that efficient E1/E2 expression and elevated plasmid replication levels during the persistent stage of infection may comprise a risk factor in HPV16-mediated oncogenesis.

Cell Line↗
PubMed1993

Intracellular expression of anti-p21ras single chain Fv fragments inhibits meiotic maturation of xenopus oocytes.

The recombinant variable regions of the monoclonal antibody Y13-259, directed against the p21ras protein, have been engineered for expression as intracellular single chain Fv fragments. The activity of the plasmid was confirmed by in vitro and in vivo translation of mRNA showing that the intracellularly expressed single chain fragments are stably and efficiently expressed as cytosolic proteins. The expression of the anti-p21ras single chain antibodies in the cytoplasm of Xenopus laevis oocytes leads to the inhibition of the insulin-induced meiotic maturation. This finding represents the first successful application of the strategy of intracellular antibodies to block a complex biological process in the cytosol of vertebrate cells.

Animals↗
PubMed1998

High-level expression of branching enzyme II from maize endosperm in Escherichia coli.

The gene that encodes the mature branching enzyme II (BEII) protein from maize (Zea mays L.) endosperm was amplified by means of a polymerase chain reaction technique and inserted into a T7-based expression vector. Although this has been an efficient expression system of maize BEII in Escherichia coli, an example is presented in this report which allows a greater expression of mBEII protein from the bacterial system by changing only one codon. The key to the level of expression appears to be related to the conversion of the third thymine base in the 285 position codon of the mBEII cDNA to cytosine without altering the encoded mBEII protein product. The crude cell extracts of enzyme prepared from E.coli exhibited seven-fold higher expression of branching enzyme activity compared to expression of the native enzyme. The enzymes from wild-type and the silent mutation genes were purified. The proteins were indistinguishable kinetically and immunologically. Thus, we obtained a significantly improved expression of mBEII protein in the bacterial system.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1996

Immobilization of manganese peroxidase from Lentinula edodes on alkylaminated Emphaze AB 1 polymer for generation of Mn3+ as an oxidizing agent.

Manganese peroxidase (MnP) is secreted by white-rot fungi and participates in the degradation of lignin by these organisms. MnP uses H2O2 as an oxidant to oxidize MnII to MnIII as the manganic ion Mn3+. The Mn3+ stabilized by chelation, is a highly reactive nonspecific oxidant capable of oxidizing a variety of toxic organic compounds. Previous attempts at immobilization of MnP, purified from Lentinula edodes through reactive amino groups, have been hindered by the protein's low lysing content of only 1% and its instability above pH 6.0. As an alternative to amine coupling, the enzyme has now been covalently immobilized through its carboxyl groups, using an azlactone-functional copolymer derivatized with ethylenediamine and 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) as a coupling reagent. The immobilization reaction was performed under acidic (pH 5.25) conditions, and 90% coupling efficiency was achieved within 2h. Net immobilization efficiencies, expressed as the product of protein coupling efficiency and enzyme activity, have been measured at > 95% within 4h. The MnP-NH-polymer and the free soluble protein were characterized and compared for their pH, temperature, and storage stabilities, as well as their H2O2 dependence and kinetics. The tethered MnP, employed in an immobilized enzyme bioreactor for generation of chelated Mn3+ may have industrial applications as a nonspecific oxidant of organopollutants.

Agaricales↗
PubMed2002

Transfection of articular chondrocytes with rhBMP7 gene and its expression.

In order to investigate the possibility of expression of exogenous gene in transduced articular chondrocytes, plasmid pcDNA3-rhBMP7 was delivered to cultured chondrocytes. Through immunohistochemical staining and RT-PCR assay, the expression of rhBMP7 gene was detected. And the bioactivity of transgene expression product was detected through MTT assay as well. It was confirmed that exogenous gene could be expressed efficiently in transduced chondrocytes and the transgene expression product had obvious bioactivity. The present study provided a theoretical basis for gene therapy on the problems of articular cartilage.

Animals↗