Biomedical subjects

Yi Gong

Publications and source records attributed to Yi Gong.

48 records · Page 3Linked to original sources

PubMed2002

Crucial step in cholesterol homeostasis: sterols promote binding of SCAP to INSIG-1, a membrane protein that facilitates retention of SREBPs in ER.

Using coimmunoprecipitation and tandem mass spectrometry, we identify INSIG-1 as an ER protein that binds the sterol-sensing domain of SREBP cleavage-activating protein (SCAP) and facilitates retention of the SCAP/SREBP complex in the ER. In sterol-depleted cells, SCAP escorts SREBPs from ER to Golgi for proteolytic processing, thereby allowing SREBPs to stimulate cholesterol synthesis. Sterols induce binding of SCAP to INSIG-1, as determined by blue native-PAGE, and this is correlated with the inhibition of SCAP exit from the ER. Overexpression of INSIG-1 increases the sensitivity of cells to sterol-mediated inhibition of SREBP processing. Mutant SCAP(Y298C) fails to bind INSIG-1 and is resistant to sterol-mediated inhibition of ER exit. By facilitating sterol-dependent ER retention of SCAP, INSIG-1 plays a central role in cholesterol homeostasis.

CCAAT-Enhancer-Binding Proteins↗

PubMed2002

2D differential in-gel electrophoresis for the identification of esophageal scans cell cancer-specific protein markers.

The reproducibility of conventional two-dimensional (2D) gel electrophoresis can be improved using differential in-gel electrophoresis (DIGE), a new emerging technology for proteomic analysis. In DIGE, two pools of proteins are labeled with 1-(5-carboxypentyl)-1'-propylindocarbocyanine halide (Cy3) N-hydroxy-succinimidyl ester and 1-(5-carboxypentyl)-1'-methylindodi-carbocyanine halide (Cy5) N-hydroxysuccinimidyl ester fluorescent dyes, respectively. The labeled proteins are mixed and separated in the same 2D gel. 2D DIGE was applied to quantify the differences in protein expression between laser capture microdissection-procured esophageal carcinoma cells and normal epithelial cells and to define cancer-specific and normal-specific protein markers. Analysis of the 2D images from protein lysates of approximately 250,000 cancer cells and normal cells identified 1038 protein spots in cancer cell lysates and 1088 protein spots in normal cell lysates. Of the detected proteins, 58 spots were up-regulated by >3-fold and 107 were down-regulated by >3-fold in cancer cells. In addition to previously identified down-regulated protein annexin I, tumor rejection antigen (gp96) was found up-regulated in esophageal squamous cell cancer. Global quantification of protein expression between laser capture-microdissected patient-matched cancer cells and normal cells using 2D DIGE in combination with mass spectrometry is a powerful tool for the molecular characterization of cancer progression and identification of cancer-specific protein markers.

Biomarkers, Tumor↗

PubMed2002

[Expression of histone-based fusion protein HNHG in E.coli].

Histone H1 contributes to condense nucleosome into super-structure during the transformation of chromatin into chromosome. It is shown in this rep or t that the fusion protein HNHG with the core of C-terminus of histone H1(0) expressed in BL21 (DE3) could also condense the plasmid DNA, just as histones did in nucleus. Under electron microscope, plasmid DNA condensed and supercoiled after t he addition of HNHG, in contrast to plasmid DNA control. This specific ability of the fusion protein HNHG of binding and condensing plasmids could be utilized to construct novel exogenous gene delivery systems. HNHG would be a promising candidate for gene delivery.

DNA, Superhelical↗

PubMed2002

[The PTD domain of Tat protein enhance GFP protein delivering into myeloma cell SP2/0].

In order to detect the protein delivery mediated by the PTD (protein transduction domain) of TAT Protein, a expression vector, named pT7460-GFP, was constructed by insert the PTD DNA Sequence, followed by a GFP (green fluorescent protein) gene fused in-frame, into the pT7450 vector. The TAT-GFP fusion protein was expressed in the E. coli ER2566. Most of the fusion protein was presented in the inclusion body. The protein was purified by Ni2+ affinity chromatography under denature conditions, then by a Sepharose Q column to remove urea. The soluble denatured protein was added directly to medium containing the Myeloma Cell SP2/0. It came out that the fusion protein could be detected delivered into the cells under fluorescent microscope in a short time.

Gene Products, tat↗

PubMed2001

An Expression Release System for Heterogeneous Proteins in E.coli Mediated by the kil Gene.

An expression release system for heterogeneous proteins in Escherichia coli mediated by the colicin release gene(kil gene) was constructed. The system is based on the ability of the Kil protein to release periplasmic proteins into the growth medium. beta-lactamase, an E.coli periplasmic protein, and prolyl endopeptidase (PEP), a periplasmic protein of Aeromonas punctata subsp. punctata were used as report proteins. Commonly, these two proteins are seldom released into the growth medium. The results indicated that the released amounts of the beta-lactamase and of the prolyl endopeptidase were nearly 5 fold and 4 fold than control, respectively.

Journal Article↗

PubMed2001

Construction of a Novel Engineering Strain E.coli G830,which is Adoptable to High-cell-density Fermentation.

A novel engineered strain G830 adoptable to high-cell-density fermentation by integrating bacterial hemoglobin vhb (Vitreoscilla hemoglobin gene) into thr operon in the chromosome of PA1 blocking Pta-Ack metabolic pathway through the homologous recombination between the homologous fragments of integrated plasmid and that of chromosome. The engineered strain G830 was characterized by phenotype observation, PCR, thr mutant, acetate acid detection, Western blotting and VHb activity assays. In high dentity fermentation, the cellular respiration, energy metabolism, highest bacterial density and dry bacteria weight of the G830 strain were markedly better than control strains PA1 and BL21. The expression of recombinant prolyl endopeptidase (PEP) in G830 and PA1 under the above condition was high and stable. Their growth situation and fermentation parameters were similar with their parental strains without plasmids, and resided plasmids maintained stably in those strains. It revealed that the integral VHb and acetate metabolism pathway (Pta-Ack) block improved the growth of host strain under low-dissolved-oxygen conditions, enhanced the recombinant proteins production and reduced the accumulation of acetate harmful to bacterial growth. In conclusion, the novel engineering strain G830 was adoptable to high cell density fermentation.

Journal Article↗

PubMed2001

The Thioredoxin Reductase-deficient E.coli Mutant Enhances Expression into Solution of Recombinant Proteins Containing Cys Residues.

A 3D artificial protein, a salmon calcitonin hexa-polymer, a salmon calcitonin octo-polymer and a human prourokinase, was expressed in the cytoplasma of E.coli GJ980(trxB(-)) mutant. These recombinant proteins containedcysteine residues of different length ranging from 12-22 residues. The mutation was mapped to the gene for thioredoxin reductase(trxB) and was found to eliminate the activity of this enzyme, which was thought to contribute to the sulfhydryl reducing potential of the cytoplasm. Recombinant salmon calcitonin hexapolymer, salmon calcitonin octo-polymer and human prourokinase had more soluble form in cytoplasm of GJ980 mutants than in wild-type strain, while 3D-protein, which has nocysteine residue, still remain in insoluble form. Results indicate the GJ980(trxB(-)) strain allowed the formation of disulphide bonds in the cell cytoplasm which is believed to encourage correct folding and soluble expression of the recombinant proteins.

Journal Article↗

PubMed2000

The Application of a Novel Lytic System to the Recovery of Recombinant Proteins in E.coli.

In order to efficiently recover recombinant proteins, a temperature-sensitive lytic system was constructed on the basis of the feature that T4 lysozyme disrupts the bacteria through cutting specific bond in the peptidoglycan layer of cell wall. This system was evaluated by constructing and introducing a low copy plasmid pSC-lys (pSC101 replication origin) into E.coli. The plasmid contained a temperature sensitive T4 lysozyme (LYS(ts)) gene under the control of three tandem tac promoters and the LacI repressor, which is compatible with other plasmids carrying pMB1, ColE1 replication origins, etc. Under the optimum lysis conditions, 2--5 fold condensed cultures resuspended in buffer A, beta-galactosidase, recombinant chaperone GroEL and ZZ-fusion salmon hexamic calcitonin (Cal6) in E.coli were released simply, rapidly, and quantitatively, as co-expressed with LYS(ts). The two tested recombinant proteins maintained their significant productions. Instead of other cumbersome lysising methods, this novel lytic system will be useful in recovery of recombinant proteins for further purification in the field of biotechnology.

Journal Article↗

PubMed2000

Increase in Hydrophobicity of Signal Peptide Enhances Secretion of Penicillin G Acylase.

An artificial strong hydrophobic signal peptide (ASP), containing ten leucines in tandem in the hydrophobic core, was utilized to replace the wild type signal peptide (WTSP) of penicillin G acylase (PAC), by the fusion to its 4 pro site. PAC expression plasmids, including pKKpacdeltaSP, pKKpacWTSP, pKKpacASP, pETpacWTSP and pETpacASP, were constructed. The length and the amino- and carboxyl-terminus amino acid composition of ASP and WTSP were kept identical. The activity assay and Western-blotting analysis were used to study the effect of ASP and WTSP on the secretion of PAC in tac, T7 and dissolved-oxygen regulation expression systems, respectively. Lack of signal peptide in pKKpacdeltaSP resulted in the accumulation of 91 kD PAC precursor (without signal peptide, but with the space peptide between alpha-subunit and beta-subunit) in the cytosol, indicating that the secretion of PAC depends on the signal peptide. In BL21(pKKpacASP) cells, the PAC activity and proprecursor (with signal peptide and space peptide) processing capacity were increased by about 54% and 38.5%, respectively, in comparison with BL21(pKKpacWTSP) cells. Compared with BL21(DE3) (pETpacWTSP), however, the PAC activity and proprecursor processing capacity in BL21(DE3) (pETpacASP) were enhanced by about 69% and 43.5%, respectively. The PAC activity expressed from pETpacASP was about 67% more than that from pETpacWTSP in the dissolved-oxygen-regulated expression system GJ100. Resulting from the strong hydrophobicity of ASP, therefore, the PAC activity and proprecursor processing capacity were increased by about 63% and 41% on average, respectively, in comparison with WTSP. In conclusion, the increase in hydrophobicity of the signal peptide hydrophobic core enhanced the secretion of penicillin G acylase.

Journal Article↗

PubMed1999

Molecular Cloning and Expression of a New A Chain of beta-Bungarotoxin.

The cDNA encoding a new A chain of beta-bungarotoxin was cloned from Bungarus multicinctus. It encoded a 27-amino acid signal peptide and a mature protein of 120 amino acids. The mature protein had the same 13 cysteines as the other A chains and shared high homology with them. The cDNA encoding the PLA(2) from Naja naja atra was also cloned by the use of the same degenerate primers. The cDNAs encoding the new A chain and the PLA(2) were highly expressed in E. coli as soluble fusion proteins and purified by affinity chromatography. The two recombinant proteins achieved after digestion by X(a) factor showed weak and strong PLA(2) activity, respectively.

Journal Article↗

PubMed1999

Molecular Cloning and Expression of the cDNA for Disintegrin from Agkistrodon acutus.

In order to clone novel and valuable genes from natural resources and develop genetic engineering drugs, total RNA was extracted from the venom gland of Agkistrodon acutus by one step method. The cDNAs for low molecular weight metalloproteinase were amplified by RT-PCR and cloned into the pGEMT vector. Their sequence were determined. One of the deduced amino acid sequences included a metalloproteinase and a disintegrin (acugrin) at the carboxyl terminus. This result further confirms that metalloproteinase and disintegrin are derived from the proenzyme of snake venom metalloproeinase. Acugrin exhibits a certain amino acid homology with other disintegrins from snake venoms. Acugrin has four disulfide bonds and a consensus motif RGD. The cDNA for the acugrin was cloned into the plasmid pT7ZZa and expressed in E.coli. ZZ-acugrin fusion protein could strongly inhibit aggregation of platelet induced by ADP and the IC(50) was about 4 nmol/L.

Journal Article↗

PubMed1998

Tumor radioimmunoimaging of chimeric antibody in nude mice with hepatoma xenograft.

AIM:To study the radioimmunoimaging (RAII) using the human/mouse chimeric Ab to evaluate its targeting activity in animal models.METHODS: To chimeric Ab was labeled with (131)I. RAII was performed at different intervals after injection of radio-labeled Abs in nude mice with human hepatoma xenograft, and tissue distribution of radioactivity was measured. Comparison was made in the chimeric Ab between the single segment Ab and previous murine mAb against HBxAg.RESULTS: The experimental objects developed tumor-positive image after 2 days of radio-labeled Abs injection, and the peak accumulation of radioactivity fell on the 7th day. The tumor/liver ratioactivity of the chimeric Ab, single segment Ab, anti-HBx mAb, and the control group was 2.81 ± 0.21, 2.44±0.16, 4.60± 0.19, and 0.96 ±0.14, respectively.CONCLUSION: The genetic engineering Abs have a considerable targeting activity which can be used as a novel humanized vector in the targeting treatment of liver cancer.

Journal Article↗