Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “expression efficiency”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 487 records · Page 27Linked to original sources
PubMed2003

[Construction of high efficient eukaryotic expression recombinant on human hepatocyte DNA synthetic stimulated factor].

OBJECTIVE: To construct the eukaryotic expression recombining vector on human The pGEM-hepatocyte DNA synthetic stimulated factor (hHDSSF) with gene cloning. METHODS: hHDSSF, a mid-recombining vector, was constructed by T-A cloning. After restriction endonuclease Not I digestion, the target fragment was subcloned into eukaryotic vector pcDNA3. 1hisB to construct the eukaryotic expression recombinant pcDNA3. 1hisB-HDSSF. RESULTS: The forward insert recombinant pcDNA3. 1hisB-HDSSF was screened and obtained with restriction endonuclease Kpn I digestion and it was detected by DNA sequence analysis. CONCLUSION: The eukaryotic expression recombinant pcDNA3. 1hisB-hHDSSF on hHDSSF is constructed successfully, which lays a foundation for building a stable eukaryotic expression cell strain and expressing hHDSSF.

Cloning, Molecular↗
PubMed2006

[Hammerhead ribozyme-mediated cleavage of transforming growth factor beta1 RNA in a cell-free system and in hepatic stellate cells].

OBJECTIVE: To identify the activity of hammerhead ribozyme against transforming growth factor beta1 (TGFbeta1) in a cell-free system and in activated hepatic stellate cells (HSCs). METHODS: The ribozyme against TGFb1 was designed with computer software. The transcripts of ribozyme, disabled ribozyme and target RNAs were prepared using the RiboMAX large scale RNA production system. The in vitro cleavage reactions were performed through incubation of 32P-labeled target RNAs with ribozyme or disabled ribozyme in different conditions. The eukaryotic expression vector encoding ribozyme and disabled ribozyme were constructed, and then transfected into HSC-T6 cells which exhibited characteristics of activated HSCs. The intracellular activity of the ribozyme was determined by detecting the ribozyme, disabled ribozyme and the TGFbeta1 expression. RESULTS: The ribozyme cleaved target RNAs into anticipated products effectively. As expected, the disabled ribozyme possessed no cleavage activity in vitro. Further study demonstrated that the ribozyme expressed efficiently and inhibited TGFbeta1 expression in activated HSCs, while the disabled ribozyme displayed only a slight effect on TGFbeta1 expression. CONCLUSION: The ribozyme with perfect cleavage activity in the cell-free system used inhibited TGFbeta1 expression effectively in activated HSCs. This ribozyme can provide a potential therapeutic approach for liver fibrosis.

Animals↗
PubMed2006

[Construction and expression of prokaryotic expression vector pTWIN1/TRAIL].

OBJECTIVE: To purify an active extracellular region of the TNF related apoptosis inducing ligand (TRAIL) protein. METHODS: According to the high-usage codons in Escherichia coli and the multiple cloning site of expression vector pTWIN1 of a self-splicing prokaryotic expression system, the extracellular region of TRAIL gene was designed and synthesized, which was cloned into pMD18-T vector. After pMD18-T/TRAIL and pTWIN1 were digested by Nru I and EcoR I, the target fragment purified was linked to the expression vector pTWIN1, which was transferred into the competent cell JM109, and positive recombination was screened. After positive recombination vector pTWIN1/TRAIL (identified with restrictive endonuclease digesting and sequencing) was transferred into the ER2566, the expression was induced by different IPTG concentration at different temperature and culture time. The expression products were analyzed by 150 g/L SDS-PAGE. RESULTS: The extracellular region of TRAIL gene was obtained by PCR, and was constructed successfully in a self-splicing prokaryotic expression vector pTWIN1/TRAIL. By 0.3 mmol/L IPTG at 15 degrees C for 14 to 16 hours, the soluble target protein was expressed efficiently. CONCLUSION: High-expression level of the extracellular region of TRAIL fusion protein was attained by use of E. coli ER2566, and the soluble target protein without any additional amino acid was successfully purified by simple treatment.

Cloning, Molecular↗
PubMed1989

Efficient surface expression of platelet GPIIb-IIIa requires both subunits.

Platelet membrane GPIIb-IIIa is a member of the integrin family of heterodimeric adhesion receptors. Processing and export of certain leukocyte and melanoma integrins is disrupted in cells lacking one subunit. We found that surface expression of GPIIb-IIIa, measured by fluorescent activated cell sorting or by surface labeling, required cotransfection of both subunits. In contrast, surface expression was not detected when the subunits were transfected individually. Immunoprecipitation of metabolically labeled transfected cells confirmed the presence of comparable levels of intracellular protein in all cases. When both subunits were transfected, post-translational cleavage of Pro-GPIIb to yield GPIIb heavy chain was also seen, while transfection with GPIIb alone resulted in coprecipitation of Pro-GPIIb with a second band that may be an endogenous beta subunit. Pro-GPIIb in these transfectants was not processed to yield GPIIb heavy chain. When transfected into COS cells alone, transiently expressed GPIIIa remained intracellular and did not appear to complex with any endogenous proteins. Thus, surface expression of processed GPIIb-IIIa depends on the presence of both subunits; the coordinate reduction of both subunits observed in some cases of Glanzmann's thrombasthenia may result from mutation affecting only one.

Animals↗
PubMed1985

Attempted expression of a human initiator tRNA gene in Saccharomyces cerevisiae.

In attempts to overproduce the wild type and, eventually, mutant human initiator methionine tRNAs for use in structure-function relationship studies, we have investigated the expression of the wild type human initiator tRNA gene in the yeast Saccharomyces cerevisiae, both in vitro and in vivo. We find that the yeast extract, while capable of accurately transcribing several yeast tRNA genes, does not transcribe the human initiator tRNA gene. In addition, when the human initiator tRNA gene is introduced into yeast as part of a 2 mu vector, no expression of the human tRNA gene was detected. A yeast alanine tRNA gene similarly introduced into yeast is expressed efficiently. The block in expression of the human tRNA gene is at the level of transcription and not processing. The yeast cell-free extract can accurately process precursors of the same human initiator tRNA made in a HeLa cell-free extract. Surprisingly, although the human tRNA gene has essentially the same intragenic control elements as the yeast initiator tRNA gene, the human tRNA gene competes extremely poorly for transcription factors in yeast extracts. In the course of screening a yeast DNA bank for initiator tRNA clones we have isolated and sequenced three yeast tRNA genes corresponding to glycine, alanine, and aspartic acid tRNAs. The sequence of glycine tRNA gene differs from the published tRNA sequence in having an additional nucleotide in the variable loop. The alanine tRNA gene codes for a new tRNA. All three genes are transcriptionally active in yeast extracts.

Base Sequence↗
PubMed2006

High guanine and cytosine content increases mRNA levels in mammalian cells.

Mammalian genes are highly heterogeneous with respect to their nucleotide composition, but the functional consequences of this heterogeneity are not clear. In the previous studies, weak positive or negative correlations have been found between the silent-site guanine and cytosine (GC) content and expression of mammalian genes. However, previous studies disregarded differences in the genomic context of genes, which could potentially obscure any correlation between GC content and expression. In the present work, we directly compared the expression of GC-rich and GC-poor genes placed in the context of identical promoters and UTR sequences. We performed transient and stable transfections of mammalian cells with GC-rich and GC-poor versions of Hsp70, green fluorescent protein, and IL2 genes. The GC-rich genes were expressed several-fold to over a 100-fold more efficiently than their GC-poor counterparts. This effect was not due to different translation rates of GC-rich and GC-poor mRNA. On the contrary, the efficient expression of GC-rich genes resulted from their increased steady-state mRNA levels. mRNA degradation rates were not correlated with GC content, suggesting that efficient transcription or mRNA processing is responsible for the high expression of GC-rich genes. We conclude that silent-site GC content correlates with gene expression efficiency in mammalian cells.

3' Untranslated Regions↗
PubMed2002

[Dual gene amplification and selection system with dihydrofolate reductase and glutamine synthetase genes effectively increase the foreign gene expression].

BACKGROUND: To study the effect of gene amplification and selection system with DHFR plus GS and DHFR or GS gene on the foreign gene expression. METHODS: Using the N-terminal truncated hTPO(T184) gene as target gene, two plasmidsre were constructed: pDC- T184 and pGC-T184 where DHFR and GS gene were used respectively as the selective amplification marker. They were cotransfected into CHO dhfr cells to establish dual gene amplification and selection system of DHFR plus GS gen and respectively transfected to establish single gene amplification and selection system of DHFR or GS gene. Three selective methods in dual selective system to compare expression efficiency of hTPO were designed: the first method (DG) was to use drug pressure of MTX, then use MSX; the second method (GD) was reversed; the third method was simultaneously to use MTX and MSX as drug pressure. RESULTS: DHFR+GS dual system had not only higher gene amplification efficiency but also higher level expression. There was no distinct affect in different method of drug pressure. CONCLUSIONS: MTX plus MSX dual drug pressure in dual selection system was an efficient and simple method to increase the expression of foreign gene in mammalian cells.

Animals↗
PubMedDate not supplied

Expression of the murine prostaglandin (PGH) synthase-1 and PGH synthase-2 isozymes in cos-1 cells.

Plasmid vectors were constructed which allowed expression of the mouse prostaglandin endoperoxide (PGH) synthase-1 and PGH synthase-2 isozymes in cos-1 cells. Efficient expression of the PGHS-2 isozyme required the truncation of the entire 3'-untranslated region of the PGHS-2 cDNA, possibly due to the presence of multiple AUUUA sequences which may destabilize the PGHS-2 mRNA. The length of the 3'-untranslated regions of the murine and ovine PGHS-1 isozymes, which do not contain AUUUA sequences, did not affect the efficiency of expression of these proteins. The murine PGHS-2 isozyme catalyzes the same cyclooxygenase and hydroperoxidase activities as the ovine and murine PGHS-1 isozymes. The maximal activities of the mouse enzymes expressed in cos-1 cells was about equal, but both were only about a third that seen with the sheep enzyme. Whether this reflects differences in the turnover rate of the mouse and sheep enzymes, or differences in the efficiency of expression in cos-1 cells is not known.

Animals↗
PubMed2005

[Cloning and expression of androgen response elements of prostate specific antigen promoter].

OBJECTIVE: To provide a possible targeted gene therapy scheme for prostate cancer, and explore the expression efficiency and tissue-specific expression of prostate specific antigen (PSA) promoter. METHODS: Three plasmids with egfp, pa-EGFP(including ARI, ARII), pba-EGFP (including ARI, ARII, ARIII) and pdeltaba-EGFP (including ARI, ARII and mutated ARIII) were designed, and the expression status was observed by transfecting into HepG2, SMMC-7721, Hela and PC-3. RESULTS: In prostate cancer cell PC-3, pba-EGFP expressed more GFP than pa-EGFP and pdeltaba-EGFP, which showed that ARIII could notably increase the transcription efficiency of PSA promoter. Further, there was no GFP expression in HepG2, SMMC-7721 and Hela transfected with pa-EGFP, p deltaba-EGFP and pba-EGFP. CONCLUSION: An expression vector based on elements of the PSA gene regulatory sequences has been developed and shown to be tightly regulated in a panel of cells from tissues of various origins. With the tissue-specific functional protein, it should provide a solid platform for clinical studies.

Androgens↗
PubMed2000

Dilution enhancement of COS cell expression cloning.

To search for an efficient expression cloning method, we mixed plasmid pmDATsv, which contains the mouse dopamine transporter (mDAT) cDNA, with a large amount of another plasmid prGlyTsv to mimic the situation of a cDNA library and examined COS cell expression. Both plasmids have an SV40 replication origin and thus will be replicated to high copy numbers in COS cells. After transfecting COS-7 cells with pmDATsv/prGlyTsv mixture at 1/1000 ratio, we could not detect any cells expressing strong mDAT activity. In contrast, when prGlyTsv was replaced by prSERTsk (no SV40 origin) in the transfection mixture, we observed hundreds of cells expressing strong mDAT activity. The results suggested that in many cells low mDAT expression was not due to the lack of pmDATsv plasmid but due to the presence of large numbers of replicable prGlyTsv. Analysis with a mathematical model suggests that diluting cDNA libraries with other plasmids without the SV40 origin should improve the detection of COS cells expressing target cDNAs. We tested this conclusion with pmDATsv/prGlyTsv mixture. When the mixture at 1/1000 ratio was diluted with prSERTsk and used for transfection, we could now easily detect cells expressing strong mDAT activity.

Animals↗
PubMed2000

Adenovirus-mediated gene transfer to cerebral circulation.

Gene therapy may, be a promising approach for treatment of cerebrovascular disease. An adenoviral vector encoding beta-galactosidase was administered intracisternally or intraventricularly into the brain of rats. Efficient expression of the reporter gene was observed at the cerebral blood vessels and perivascular tissues. When the adenoviral vector was delivered into CSF of dogs suffering from subarachnoid hemorrhage, prominent expressions of transgene were observed. Introduction of the vector to the ischemic brain of rats provided efficient transgene expression in the peri-ischemic area. Therefore, gene transfer to the cerebral blood vessel and brain may be a promising approach for gene therapy of stroke. Atherosclerotic lesion plays an important role in stroke. We evaluated efficacy of adenovirus-mediated gene transfer to the atherosclerotic vessels from monkeys and rabbits using an ex vivo gene transfer system. Efficiency of transgene expression in the atherosclerotic endothelium was better than that of normal vessels in both animals. Thus, the endothelium of atherosclerotic vessels may be a good target for gene therapy. Next, we transfected atherosclerotic carotid arteries from rabbits with an adenoviral vector encoding endothelial nitric oxide synthase (eNOS). After overexpression of eNOS in the atherosclerotic arteries, the response to acetylcholine was augmented, showing similar relaxation with normal vessels. These results suggest that gene transfer to atherosclerotic vessels improves endothelial function, which may be a new therapeutic approach for cerebrovascular disease.

Adenoviridae↗
PubMed1995

Role of glycosylation in the expression of human procathepsin D.

Human procathepsin D carries two N-linked glycosylation sites at asparagine residues 70 and 199, widely separated on the surface of the folded protein. We created monoglycosylated procathepsin D molecules by site-directed mutagenesis in vitro of the individual glycosylation sites. With only two exceptions, all 12 mutants of this type were expressed efficiently in mammalian cells. The expressed proteins were stable, targeted to the lysosome, and partially secreted into the medium. When both glycosylation sites were eliminated, however, the expressed proteins (9 different mutants) were stable but most were not secreted and targeted poorly to the lysosome. Mammalian fibroblasts appear to sort nascent procathepsin D efficiently only if it is N-glycosylated. Procathepsin D monoglycosylated at N70 is readily distinguished from the endogenous protein in transfected human cells and thus provides an excellent substrate for studying lysosomal targeting in an homologous system.

Animals↗
PubMed2002

Stable expression of primary human immunodeficiency virus type 1 structural gene products by use of a noncytopathic sindbis virus vector.

Efficient expression of the human immunodeficiency virus type 1 (HIV-1) structural gene products Gag, Pol, and Env involves the regulation by viral Rev and Rev-responsive elements (RRE). Removal of multiple inhibitory sequences (INS) in the coding regions of these structural genes or modification of the codon usage patterns of HIV-1 genes to those used by highly expressed human genes has been found to significantly increase HIV-1 structural protein expression in the absence of Rev and RRE. In this study, we show that efficient and stable expression of the HIV-1 structural gene products Gag and Env could be achieved by transfection with a noncytopathic Sindbis virus expression vector by using HIV-1 sequences from primary isolates without any sequence modification. Stable expression of these Gag and Env proteins was observed for more than 12 months. The fact that the Sindbis virus expression vector replicates its RNA only in the cytoplasm of the transfected cells and the fact that the lack of expression of HIV-1 Gag by the DNA vector containing unmodified HIV-1 gag sequences was associated with a lack of detectable cytoplasmic gag RNA suggest that a major blockage in the expression of HIV-1 structural proteins in the absence of Rev/RRE is caused by inefficient accumulation of mRNA in the cytoplasm. Efficient long-term expression of structural proteins of diverse HIV-1 strains by the noncytopathic Sindbis virus expression system may be a useful tool for functional study of HIV-1 gene products and vaccine research.

Animals↗
PubMed1993

Human neuronal voltage-dependent calcium channels: studies on subunit structure and role in channel assembly.

Voltage-dependent calcium (Ca2+) channels, expressed in the CNS, appear to be multimeric complexes comprised of at least alpha 1, alpha 2 and beta subunits. Previously, we cloned and expressed human neuronal alpha 1, alpha 2 and beta subunits to study recombinant channel complexes that display properties of those expressed in vivo. The alpha 1B-mediated channel subtype binds omega-conotoxin (CgTx) GVIA with high affinity and exhibits properties of N-type voltage-dependent Ca2+ channels. Here we describe several alpha 2 and beta splice variants and report results on the expression of omega-CgTx GVIA binding sites, assembly of the subunit complex and biophysical function of alpha 1B-mediated channel complexes containing some of these splice variants. We optimized recombinant expression in human embryonic kidney (HEK) 293 cells of alpha 1B alpha 2b beta 1 subunit complexes by controlling the expression levels of subunit mRNAs and monitored cell surface expression by binding of omega-CgTx GVIA to the alpha 1B subunit. Co-expression of either alpha 2b or beta 1 subunits with an alpha 1B subunit increased expression of binding sites while the most efficient expression was achieved when both alpha 2b and beta 1 subunits were co-expressed with an alpha 1B subunit. The presence of alpha 2b affects the affinity of omega-CgTx GVIA binding and barium (Ba2+) current magnitudes, although it does not appear to alter kinetic properties of the Ba2+ current. This is the first evidence of an alpha 2 subunit modulating the binding affinity of a cell-surface Ca2+ channel ligand. Our results demonstrate that alpha 1, alpha 2 and beta subunits together contribute to the efficient assembly and functional expression of voltage-dependent Ca2+ channel complexes.

Amino Acid Sequence↗
PubMed1994

Baculovirus mediated high level expression of human placental aromatase (CYP19A1).

An efficient expression system for a cDNA clone of human placental aromatase has been developed using the baculovirus expression system in TN5 (Tricoplusia ni) cells. The protein was expressed at high levels, with specific aromatase activity and specific P450 content comparable to that found in human placental microsomes. To achieve these high levels of activity, hemin had to be added to the cultures of infected cells and NADPH-cytochrome P450 reductase had to be included in the assay buffer. The spectral properties of ligand bound forms of the baculovirus expressed aromatase were very similar to those exhibited by the same ligand bound forms of the enzyme purified from placental microsomes. This expression system appears to be a suitable source for the purification of milligram quantities of recombinant aromatase.

Animals↗
PubMed1991

Functional expression of the alpha 1 subunit of the AMPA-selective glutamate receptor channel, using a baculovirus system.

Using a baculovirus expression vector system, the alpha 1 subunit of the mouse AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate)-selective glutamate receptor channel was expressed in insect Spdoptera frugiperda cells. Binding studies using [3H]AMPA showed that insect cells infected with the recombinant virus expressed approximately 1.8 x 10(5) binding sites per cell on their surface. The ligand binding characteristics of the receptors expressed in insect cells were examined. The baculovirus-insect cell expression system affords high-efficiency expression of the receptor in sufficient amounts to permit structural and functional analyses.

Animals↗
PubMed1994

Expression and characterization of the alpha 2 subunit of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-selective glutamate receptor channel in a baculovirus system.

Using a baculovirus expression vector system, the alpha 2 subunit of the mouse alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-selective glutamate receptor (GluR) channel was expressed in Spodoptera frugiperda insect cells. Immunoblotting using the antibody made to the synthetic peptide corresponding to the C-terminus of GluR alpha 2 and [35S]methionine/[35S]cysteine metabolic radiolabeling revealed the major 102-kDa and the minor 98-kDa protein bands. Metabolic radiolabeling with tunicamycin suggested that the two bands correspond to glycosylated and unglycosylated forms, respectively. The recombinant GluR alpha 2 proteins expressed in insect cells were also identified by immunofluorescence staining. The results of [3H]AMPA binding assay using whole cells suggested that, in infected Sf21 cells, binding sites of the GluR alpha 2 proteins were possibly located on the extracellular side. Scatchard analysis of AMPA binding showed the following parameters: Kd = 16 nM, Bmax = 1.9 x 10(5) binding sites per cell or 1 pmol/mg protein in the total particulate fraction. The ligand binding characteristics of the receptors expressed in insect cells were examined. From the effect of various agonists on [3H]AMPA binding of the receptors expressed in insect cells, the rank order potency of agonists was quisqualate > AMPA > L-glutamate > kainate. Thus, the baculovirus-insect cell expression system provides high-efficiency expression of the receptor sufficient to permit structural and functional analyses.

Animals↗