SV40 Expression Vector Research Articles

Histological, immunohistochemical, and ultrastructural features of a rat medullary thyroid carcinoma transfected with a corticotropin-releasing hormone cDNA expression vector.

Clonal cell lines producing corticotropin-releasing hormone (CRH) have been generated by transfection of the W2 rat medullary thyroid carcinoma (MTC) cell with a CRH-encoding CMV/ SV40 expression vector. Here, we report the morphological, immunohistochemical, and ultrastructural features of rat tumors derived by implantation of CRH-producing W2CRH-7 cells and compare them with non-CRH-producing W2 MTCs. Both types of tumors grew rapidly and consisted of sheets and nests of pleomorphic cells infiltrating adjacent adipose tissue. Immunohistochemistry revealed CRH in only W2CRH-7 tumors; scattered cells in these tumors also were immunoreactive for chromogranin and for vasoactive intestinal peptide. Otherwise, the two tumor types exhibited similar profiles of various neuroendocrine markers, including neuron-specific enolase, synaptophysin, calcitonin, and somatostatin. Ultrastructurally, the tumors contained abundant dilated rough endoplasmic reticulum, a prominent Golgi apparatus, and numerous lysosomes. Very few secretory granules were noted in the W2 tumors; by contrast, secretory granules, although still not numerous in the majority of W2CRH-7 cells, were more abundant in scattered cells of those tumors. The positive immunostaining for CRH is consistent with the observations of increased plasma CRH and pituitary-adrenal activation induced by these transplanted tumors. This system provides a valuable model for CRH excess mimicking tumoral CRH-dependent Cushing's syndrome in human patients.

High-efficiency expression of mammalian β-adrenergic receptors in baculovirus-infected insect cells

Infection of a clonal isolate of Spodoptera frugiperda cells (Sf9) with a baculovirus expression vector harboring the cDNA encoding the β-adrenergic receptor resulted in a high efficiency expression. At 48 hr post-infection, the level of expression of β-adrenergic receptors was ∼12 million/cell. Specific activities of crude lysates of infected Sf9 cells were ∼30 pmol/mg of protein, 5-fold greater than those of membranes of high-expressor Chinese hamster ovary cells stably transfected with an SV-40 expression vector. One liter of infected Sf9 cells expresses 20–40 nmol of receptor. Autoradiography of membranes incubated with the β-adrenergic antagonist [ 125I]iodoazidobenzylpindolol, photolyzed, and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed 46,000- (presumably unglycosylated) and 48,000-M r peptides for Sf9 cells as compared to ∼65,000-M r for Chinese hamster ovary cells. The baculovirus Sf9 system provides high-efficiency expression of receptor sufficient to permit physicochemical analyses.

4777240 SV40 expression vector containing HBxAg as an expression marker: Ann Moriarty, Hanna Alexander, Richard Lerner assigned to Scripps Clinic and Research Foundation

4777240 SV40 expression vector containing HBxAg as an expression marker: Ann Moriarty, Hanna Alexander, Richard Lerner assigned to Scripps Clinic and Research Foundation

Construction and expression of a hybrid plasminogen activator gene with sequences from non-protease region of tissue-type plasminogen activator (t-PA) and protease region of urokinase (u-PA)

There are two physiological plasminogen activators (PAs), tissue-type PA (t-PA) and urokinase (u-PA) which possess distinct immunological and biochemical characteristics. Using genetic engineering techniques a hybrid t : u-PA cDNA, comprised of amino acid (aa) sequences corresponding to the non-protease region (aa 1–261) of t-PA and the protease region (aa 132–411) of u-PA, was constructed. The t : u-PA gene after insertion into the SV40 expression vector was expressed in monkey Cos-1 cells. The 66–67 kDa t : u-PA was produced in an enzymatically active form. The fibrinolytic activity of the t : u-PA could be quenched by anti-urokinase as well as by anti-t-PA sera. Like urokinase, the t : u-PA showed a high intrinsic plasminogen activation. This activity, as m the case of t-PA, was stimulated by fibrin. The u-PA, on the other hand, stimulated plasminogen activation marginally in the presence of fibrin. Both the t : u-PA and t-PA showed binding affinity for fibrin clot. This study strongly suggests the autonomous nature of the structural domains in PA and also demonstrates the feasibility of shuffling these domains without loss of their functional activities.

Isolation and sequence of a cDNA for human pro-(cathepsin L).

The major excreted protein (MEP) of malignantly transformed mouse fibroblasts is the precursor to an acid proteinase with enzymic specificity similar to that of human cathepsin L. By cross-hybridization with a mouse MEP sequence, cDNA clones of the human form of MEP in an SV40 expression vector were isolated. A 1.6 kb cDNA showed 70% deduced amino acid sequence identity with mouse MEP. The deduced amino acid sequence of the cloned human MEP was the same, except for two amino acids, as the N-terminal sequence of mature human cathepsin L, thereby establishing that human MEP is human pro-(cathepsin L). Use of this human pro-(cathepsin L) cDNA clone allowed the detection of a 1.6-1.8 kb pro-(cathepsin L) mRNA in human cells which was not detected with a mouse pro-(cathepsin L) probe.

Determination of the epitope 264 on the hemagglutinin molecule of influenza H1N1 virus by site-specific mutagenesis

Full-length cDNA of HA gene derived from B-1-23 virus, a variant of A/USSR/90/77 (A/USSR/77) (H1N1) which had been selected with monoclonal antibody (mAb) 264 and contained an amino acid change at position 190 of the HA1 region, was cloned into the SV40 expression vector. Hemabsorbing or fusion activities of the HA protein expressed on CV-1 cells infected with the recombinant virus were indistinguishable from those of the authentic HA protein on B-1-23 virus infected cells. The antigenicity of the expressed HA protein was examined with five monoclonal antibodies to the HA of A/USSR/77 virus. The HA protein reacted with all mAbs except for mAb 264. To define the area of epitope 264, we prepared seven HA cDNAs modified by site-specific mutagenesis and cloned them into the SV40 expression vector (SVHA). The single base change from G to A at position 642 of B-1-23 HA cDNA replaced Asn at position 190 of the HA protein with Asp. The resulting HA protein, the amino acid sequence of which was the same as that in A/USSR/77, regained the binding activity with mAb 264. F. L. Raymond et al. (1984 In “Segmented Negative Strand Viruses” (R. W. Compans and D. H. L. Bishop, Eds.), pp.253–258, Academic Press, Orlando; 1986, Virology 148, 275–287) and A. P. Kendal et al. (1984 , In “Modern Approaches to Vaccines,” pp. 151–157, Harvard Univ. Press, Cambridge) showed that changed amino acid residues 219(Lys) and 227(Glu) in A/Brazil/11/78 and 189(Lys) and 225(Asp) in A/Lackland/3/78 were presumably included in the area of epitope 264 by the nucleotide sequence analysis. Of those amino acids, our results show it is the residues 190 and 219 and possibly residue 189 that are involved in the epitope 264, but neither residue 225 nor 227.

8503950 A SV40 expression vector containing hbxag as an expression marker

8503950 A SV40 expression vector containing hbxag as an expression marker

8503950 A SV40 expression vector containing HBxAG as an expression marker: Ann M Moriarty, Hannah Alexander, Richard A Lerner assigned to Scripps Clinic and Research Foundation

8503950 A SV40 expression vector containing HBxAG as an expression marker: Ann M Moriarty, Hannah Alexander, Richard A Lerner assigned to Scripps Clinic and Research Foundation

Biologic Properties of Molecularly Cloned and Expressed Murine Interleukin-3

Interleukin-3 (IL-3) (multipotential colony-stimulating factor [multi-CSF] ) is an important regulator of hemopoiesis. We recently isolated a cDNA clone of this gene and describe in this manuscript the biologic properties of the expressed gene product. An SV40 expression vector carrying cDNA encoding murine interleukin-3 was constructed so that expression of the IL-3 gene was placed under the control of the SV40 early promoter. When the expression vector was transfected to COS-1 monkey cells, IL-3 activity was secreted into the medium, reaching maximal levels 72 hours after transfection. The IL-3 produced by the COS-1 cells was partially purified using diethylaminoethyl Sephacel and phenyl-Sepharose, and its chromatographic properties were the same as IL-3 produced by the WEHI-3 cell line. The biologic activities of the "expressed" IL-3 include the "induction" of 20-alpha-hydroxysteroid dehydrogenase (20-alpha-SDH) in splenic lymphocytes from nu/nu mice, proliferative activity for 32D cl-23 and FDC-P1 cell lines, and colony-stimulating activity for granulocyte-macrophage, eosinophil, megakaryocyte, natural killer-like, erythroid, and multipotential colony-forming cells from murine fetal liver and adult bone marrow.

Antibodies to peptides detect new hepatitis B antigen: serological correlation with hepatocellular carcinoma.

The expression of a previously unidentified gene product, encoded by the hepatitis B virus (HBV) genome, has been achieved with a recombinant SV40 expression vector. Antibodies against synthetic peptides representing defined regions of this protein were used to screen cells infected with recombinant virus as well as tissues naturally infected with HBV. A 24,000-dalton protein (p24) was detected in cells infected with recombinant virus and a 28,000-dalton protein (p28) was detected in tissues infected with HBV. The peptides or recombinant-derived protein were used as antigens to screen sera from individuals infected with HBV. Specific antibodies were detected predominantly in sera from patients with hepatocellular carcinoma. The presence of p28 in tissues infected with HBV and the appearance of specific antibodies in infectious sera establish the existence of an additional marker for HBV infection.

Expression of preprosomatostatin in heterologous cells: Biosynthesis, posttranslational processing, and secretion of mature somatostatin

Somatostatin is a 14 amino acid peptide hormone that is synthesized as part of a larger precursor, preprosomatostatin, which comprises about 120 amino acids. The overall organization of the precursor is conserved in many species in that it consists of a signal peptide followed by a proregion of 90–100 amino acids and the mature hormone is located at the carboxyl terminus of the molecule. To understand the role of the propeptide in generating the mature hormone, we have used gene-transfer experiments to introduce angler fish preprosomatostatin into mammalian cells. Here we report the results of transfection of COS-7 cells with an SV40 expression vector containing preprosomatostatin cDNA cloned into the VP-1 late gene. Analysis of the parameters of somatostatin gene expression showed that COS cells synthesized prosomatostatin, which was detected intracellularly; the prosomatostatin was proteolytically processed to mature somatostatin; and the mature hormone was secreted by the COS cells into the tissue culture medium. Our results suggest that COS cells, which do not normally secrete polypeptide hormones, contain the necessary proteolytic processing enzymes to convert preprosomatostatin to the mature hormone and the cellular apparatus necessary for its secretion.

Mutations of the Rous sarcoma virus env gene that affect the transport and subcellular location of the glycoprotein products.

The envelope glycoproteins of Rous sarcoma virus (RSV), gp85 and gp37, are anchored in the membrane by a 27-amino acid, hydrophobic domain that lies adjacent to a 22-amino acid, cytoplasmic domain at the carboxy terminus of gp37. We have altered these cytoplasmic and transmembrane domains by introducing deletion mutations into the molecularly cloned sequences of a proviral env gene. The effects of the mutations on the transport and subcellular localization of the Rous sarcoma virus glycoproteins were examined in monkey (CV-1) cells using an SV40 expression vector. We found, on the one hand, that replacement of the nonconserved region of the cytoplasmic domain with a longer, unrelated sequence of amino acids (mutant C1) did not alter the rate of transport to the Golgi apparatus nor the appearance of the glycoprotein on the cell surface. Larger deletions, extending into the conserved region of the cytoplasmic domain (mutant C2), resulted in a slower rate of transport to the Golgi apparatus, but did not prevent transport to the cell surface. On the other hand, removal of the entire cytoplasmic and transmembrane domains (mutant C3) did block transport and therefore did not result in secretion of the truncated protein. Our results demonstrate that the C3 polypeptide was not transported to the Golgi apparatus, although it apparently remained in a soluble, nonanchored form in the lumen of the rough endoplasmic reticulum; therefore, it appears that this mutant protein lacks a functional sorting signal. Surprisingly, subcellular localization by internal immunofluorescence revealed that the C3 protein (unlike the wild type) did not accumulate on the nuclear membrane but rather in vesicles distributed throughout the cytoplasm. This observation suggests that the wild-type glycoproteins (and perhaps other membrane-bound or secreted proteins) are specifically transported to the nuclear membrane after their biosynthesis elsewhere in the rough endoplasmic reticulum.

Tissue specificity of the initiation of immunoglobulin kappa gene transcription.

The transient transcription of a rearranged mouse immunoglobulin kappa gene was studied in a monkey fibroblast cell line. The gene was inserted into an SV40 expression vector and the calcium phosphate coprecipitation method was used for transfection. The transcripts were correctly spliced; transcription, however, was initiated within the vector and not at the correct site 23-26 bp upstream of the gene, irrespective of the length of the upstream sequences (90, 160, 370, and 870 bp) in the plasmid constructs. In contrast, accurately initiated transcripts were observed when a plasmid containing the kappa gene with 870 bp of its upstream sequence was introduced into a lymphoid cell line; the plasmid was constructed from the pSV2-gpt vector and the electric impulse method was used for gene transfer in most experiments. Tissue-specific expression of kappa light chain genes in lymphoid cells is known to depend on the presence of an enhancer element in the J-C intron. The results reported in this paper suggest that the sequence elements pd and dc which are located upstream of the leader gene segment also act in a tissue-specific manner and that it is the initiation of transcription which is a tissue-specific event.

Isolation of stable mouse cell lines that express cell surface and secreted forms of the vesicular stomatitis virus glycoprotein.

We have characterized two stable transformed mouse cell lines (CG1 and CTG1) that express either the normal vesicular stomatitis virus glycoprotein (G) or a truncated form of the G protein (TG) that lacks the COOH-terminal anchor sequences and is secreted from the cells. These cell lines were obtained using a hybrid vector consisting of the transforming DNA fragment of bovine papilloma virus linked to a segment of the SV40 expression vector pSV2 containing cloned cDNA encoding either the normal or truncated form of the vesicular stomatitis virus G protein. Using indirect immunofluorescence we have found that greater than 95% of the cells in each line express the G protein(s), although the level of expression within the population is variable. The normal G protein expressed in these cells obtains its complex oligosaccharides in less than 30 min and is transported to the cell surface. In contrast, the TG protein obtains its complex oligosaccharides with a half-time of about 2.5 h. Immunofluorescence data show an apparent concentration of the TG protein in the rough endoplasmic reticulum. These data together suggest that transfer of this anchorless protein from the rough endoplasmic reticulum to the Golgi apparatus is the rate-limiting step in its secretion. We observed, in addition to normal G protein, two smaller G-related proteins produced in the CG1 cell line. We suggest that these proteins could result from aberrant splicing from sites within the G mRNA sequence to the downstream acceptor in the pSV2 vector.