scholarly journals Use of the Escherichia coli gene for asparagine synthetase as a selective marker in a shuttle vector capable of dominant transfection and amplification in animal cells.

1987 ◽  
Vol 7 (5) ◽  
pp. 1623-1628 ◽  
Author(s):  
M Cartier ◽  
M W Chang ◽  
C P Stanners
Keyword(s):  
Escherichia Coli ◽  
Cell Lines ◽  
Animal Cell ◽  
Chinese Hamster ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Asparagine Synthetase ◽  
Translational Initiation ◽  
Shuttle Vectors ◽  
Advantages And Disadvantages

A new dominant amplifiable selective system for use in bacterium-animal cell shuttle vectors was developed by the insertion of a 2-kilobase genomic fragment containing the cloned Escherichia coli gene for asparagine synthetase (AS) into the pBR322-simian virus 40 recombinant vector pSV2 so as to place the translational initiator codon for the bacterial AS about 1,000 base pairs downstream from the simian virus 40 early promoter. This new construct, pSV2-AS, retains bacterial sequences for transcriptional and translational initiation and so can express AS in bacteria. The construct can also complement AS- mutants of mammalian cells, giving AS+ transfectants capable of growth in medium lacking asparagine, with relatively high efficiency (about 300 colonies per microgram of DNA per 10(6) cells exposed). The vector can be amplified up to 100-fold in such AS+ transfectants by selection in asparagine-free medium containing increasing concentrations of the AS inhibitor beta-aspartyl hydroxamate. AS+ transfectants were found to be much more resistant to a second AS inhibitor, Albizziin, than were normal AS+ animal cell lines. This difference, which may indicate a strong resistance of the bacterial AS enzyme to Albizziin, was exploited to develop an effective selection for bacterial AS transfectants of a number of wild-type AS+ cell lines of rat, Chinese hamster, mouse, and human origin. LR-73 cells, a Chinese hamster AS+ cell line, were transfected with pSV2-AS with an efficiency of about 1,000 colonies per 0.5 microgram of DNA per 10(6) cells. The integrated construct in these cells was amplified by incubation of the transfectants in increasing concentrations of beta-aspartyl hydroxamate. Advantages and disadvantages of this new dominant, selectable, and amplifiable marker over markers commonly used in shuttle vectors are discussed.

Use of the Escherichia coli gene for asparagine synthetase as a selective marker in a shuttle vector capable of dominant transfection and amplification in animal cells

1987 ◽  
Vol 7 (5) ◽  
pp. 1623-1628
Author(s):  
M Cartier ◽  
M W Chang ◽  
C P Stanners
Keyword(s):  
Escherichia Coli ◽  
Cell Lines ◽  
Animal Cell ◽  
Chinese Hamster ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Asparagine Synthetase ◽  
Translational Initiation ◽  
Shuttle Vectors ◽  
Advantages And Disadvantages

A new dominant amplifiable selective system for use in bacterium-animal cell shuttle vectors was developed by the insertion of a 2-kilobase genomic fragment containing the cloned Escherichia coli gene for asparagine synthetase (AS) into the pBR322-simian virus 40 recombinant vector pSV2 so as to place the translational initiator codon for the bacterial AS about 1,000 base pairs downstream from the simian virus 40 early promoter. This new construct, pSV2-AS, retains bacterial sequences for transcriptional and translational initiation and so can express AS in bacteria. The construct can also complement AS- mutants of mammalian cells, giving AS+ transfectants capable of growth in medium lacking asparagine, with relatively high efficiency (about 300 colonies per microgram of DNA per 10(6) cells exposed). The vector can be amplified up to 100-fold in such AS+ transfectants by selection in asparagine-free medium containing increasing concentrations of the AS inhibitor beta-aspartyl hydroxamate. AS+ transfectants were found to be much more resistant to a second AS inhibitor, Albizziin, than were normal AS+ animal cell lines. This difference, which may indicate a strong resistance of the bacterial AS enzyme to Albizziin, was exploited to develop an effective selection for bacterial AS transfectants of a number of wild-type AS+ cell lines of rat, Chinese hamster, mouse, and human origin. LR-73 cells, a Chinese hamster AS+ cell line, were transfected with pSV2-AS with an efficiency of about 1,000 colonies per 0.5 microgram of DNA per 10(6) cells. The integrated construct in these cells was amplified by incubation of the transfectants in increasing concentrations of beta-aspartyl hydroxamate. Advantages and disadvantages of this new dominant, selectable, and amplifiable marker over markers commonly used in shuttle vectors are discussed.

scholarly journals Cell-Specific Modulation of Papovavirus Replication by Tumor Suppressor Protein p53

2000 ◽  
Vol 74 (10) ◽  
pp. 4688-4697 ◽  
Author(s):  
Dina Lepik ◽  
Mart Ustav
Keyword(s):  
Tumor Suppressor ◽  
Cell Lines ◽  
P53 Protein ◽  
Chinese Hamster ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
T Antigen ◽  
S Phase ◽  
Human Papillomaviruses ◽  
Mouse Cells

ABSTRACT Small DNA tumor viruses like human papillomaviruses, simian virus 40, and adenoviruses modulate the activity of cellular tumor suppressor proteins p53 and/or pRB. These viruses replicate as nuclear multicopy extrachromosomal elements during the S phase of the cell cycle, and it has been suggested that inactivation of p53 and pRb is necessary for directing the cells to the S phase. Mouse polyomavirus (Py), however, modulates only the pRB protein activity without any obvious interference with the action of p53. We show here that Py replication was not suppressed by the p53 protein indeed in all tested different mouse cell lines. In addition, E1- and E2-dependent papillomavirus origin replication was insensitive to the action of p53 in mouse cells. We show that in hamster (Chinese hamster ovary) or human (osteosarcoma 143) cell lines the replication of both Py and papillomavirus origins was efficiently blocked by p53. The block of Py replication in human and hamster cells is not caused by the downregulation of large T-antigen expression. The deletion analysis of the p53 protein shows that the RPA binding, proline-rich regulatory, DNA-binding, and oligomerization domains are necessary for p53 action in both replication systems. These results indicate that in mouse cells the p53 protein could be inactive for the suppression of papovavirus replication.

scholarly journals Expression of Escherichia coli homoserine kinase in mouse 3T3 cells

1992 ◽  
Vol 281 (3) ◽  
pp. 865-870 ◽  
Author(s):  
W D Rees ◽  
S M Hay ◽  
H J Flint
Keyword(s):  
Escherichia Coli ◽  
Animal Cell ◽  
Intact Cell ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Eukaryotic Expression ◽  
3T3 Cells ◽  
E Coli ◽  
Homoserine Kinase ◽  
Neomycin Resistance

The Escherichia coli gene for homoserine kinase (thrB) has been cloned into a simian-virus-40-based eukaryotic expression vector which also includes a neomycin-resistance gene. Mouse 3T3 cells transfected with this plasmid were selected for resistance and screened for homoserine kinase activity. It has thus been possible to isolate clones which are capable of accumulating homoserine O-phosphate when supplied with homoserine. In broken-cell preparations the kinetic constants for the production of homoserine O-phosphate were similar to those of the wild-type E. coli enzyme. These experiments demonstrate that E. coli homoserine kinase can be expressed in an animal cell and that it can successfully phosphorylate L-homoserine in the intact cell utilizing endogenous ATP.

scholarly journals Analysis of a transgenic mouse containing simian virus 40 and v-myc sequences.

1985 ◽  
Vol 5 (4) ◽  
pp. 642-648 ◽  
Author(s):  
J A Small ◽  
D G Blair ◽  
S D Showalter ◽  
G A Scangos
Keyword(s):  
Cell Lines ◽  
Choroid Plexus Papilloma ◽  
Simian Virus 40 ◽  
Soft Agar ◽  
Simian Virus ◽  
T Antigen ◽  
Primary Cell ◽  
Tissue Samples ◽  
Primary Cell Lines

Two plasmids, one containing the simian virus 40 (SV40) genome and the mouse metallothionein I gene and one containing the v-myc gene of avian myelocytomatosis virus MC29, were coinjected into mouse embryos. Of the 13 surviving mice, one, designated M13, contained both myc and SV40 sequences. This mouse developed a cranial bulge identified as a choroid plexus papilloma at 13 weeks and was subsequently sacrificed; tissue samples were taken for further analysis. Primary cell lines derived from these tissues contained both myc and SV40 DNA. No v-myc mRNA could be detected, although SV40 mRNA was present in all of the cell lines tested. T antigen also was expressed in all of the cell lines analyzed. These data suggest that SV40 expression was involved in the abnormalities of mouse M13 and was responsible for the transformed phenotype of the primary cell lines. Primary cell lines from this mouse were atypical in that the population rapidly became progressively more transformed with time in culture based on the following criteria: morphology, growth rate, and the ability to grow in soft agar and in serum-free medium. The data also suggest that factors present in the mouse regulated the ability of SV40 to oncogenically transform most cells and that in vitro culture of cells allowed them to escape those factors.

scholarly journals Simian Virus 40 Late Proteins Possess Lytic Properties That Render Them Capable of Permeabilizing Cellular Membranes

2006 ◽  
Vol 80 (13) ◽  
pp. 6575-6587 ◽  
Author(s):  
Robert Daniels ◽  
Nasser M. Rusan ◽  
Anne-Kathrin Wilbuer ◽  
Leonard C. Norkin ◽  
Patricia Wadsworth ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Plasma Membranes ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Cellular Membranes ◽  
Bacterial Membranes ◽  
Cell Death Pathways ◽  
Late Protein ◽  
Temporally Correlated ◽  
Infectious Cycle

ABSTRACT Many nonenveloped viruses have evolved an infectious cycle that culminates in the lysis or permeabilization of the host to enable viral release. How these viruses initiate the lytic event is largely unknown. Here, we demonstrated that the simian virus 40 progeny accumulated at the nuclear envelope prior to the permeabilization of the nuclear, endoplasmic reticulum, and plasma membranes at a time which corresponded with the release of the progeny. The permeabilization of these cellular membranes temporally correlated with late protein expression and was not observed upon the inhibition of their synthesis. To address whether one or more of the late proteins possessed an inherent capacity to induce membrane permeabilization, we examined the permeability of Escherichia coli that separately expressed the late proteins. VP2 and VP3, but not VP1, caused the permeabilization of bacterial membranes. Additionally, VP3 expression resulted in bacterial cell lysis. These findings demonstrate that VP3 possesses an inherent lytic property that is independent of eukaryotic signaling or cell death pathways.

DNA methylation patterns associated with asparagine synthetase expression in asparagine-overproducing and -auxotrophic cells

1989 ◽  
Vol 9 (7) ◽  
pp. 2922-2927
Author(s):  
I L Andrulis ◽  
M T Barrett
Keyword(s):  
Cell Lines ◽  
Chinese Hamster Ovary Cells ◽  
Methylation Status ◽  
Chinese Hamster ◽  
Resistant Cell ◽  
Methylation Pattern ◽  
Asparagine Synthetase ◽  
Synthetase Activity ◽  
Dna Hypomethylation ◽  
Ovary Cells

In Chinese hamster ovary cells, the gene for asparagine synthetase, which spans 20 kilobase pairs, was found to contain a cluster of potential sites for CpG methylation in a 1-kilobase-pair region surrounding the first exon. Fourteen of the sites that could be assayed for methylation by MspI-HpaII digestions were found in this region, with an additional nine MspI sites spread throughout the remainder of the gene. The methylation status of the gene was analyzed in a series of cell lines that differed in the amount of asparagine synthetase activity. The level of expression showed a direct correlation with the extent of methylation of a subset of the MspI sites found in the 5' region of the gene. The rest of the gene was completely methylated in most cell lines. Wild-type cells, which expressed a basal level of asparagine synthetase activity, were partially demethylated in the 5' region. In contrast, asparagine-requiring N3 cells, which lacked detectable mRNA for asparagine synthetase, were methylated throughout the entire gene. Spontaneous revertants of strain N3, selected for growth in asparagine-free medium, exhibited extensive hypomethylation of the asparagine synthetase gene. The methylation pattern of the gene in cell lines that overproduced the enzyme was also examined. Albizziin-resistant cell lines, which had amplified copies of the gene, were extensively demethylated in the 5' region. Overexpression of asparagine synthetase in beta-aspartyl hydroxamate-resistant lines without amplified copies of the gene was also correlated with DNA hypomethylation.

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