Integration, amplification and stability of plasmid sequences in CHO cell cultures.
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Animals↗
Biomedical subjects
F M Wurm
Publications and source records attributed to F M Wurm.
Presence and transcription of intracisternal A-particle-related sequences in CHO cells.
We have characterized sequences expressed in Chinese hamster ovary (CHO) cells which are related to the intracisternal A-particle (IAP) genes of mice and Syrian hamsters. Several cDNA clones homologous to Syrian hamster IAP probes have been isolated and used to evaluate the abundance and expression of these retroviruslike sequences. DNA blot analysis with homologous Chinese hamster IAP probes revealed that IAP-related sequences are present in CHO cell DNA at moderately repetitive levels (approximately 300 copies per haploid genome). Sequence analysis has revealed the existence of at least two distinct families of IAP-related sequences in CHO cell DNA. Family I sequences exhibit identical 4.5-kilobase-pair internal deletions relative to complete IAP genomes of mice or Syrian hamsters, but family II sequences showed no major sequence discontinuities relative to the IAP genes of other species. Both families are expressed as abundant cytoplasmic RNA in CHO cells, but only family II sequences produce abundant transcripts of a size consistent with that of a full-length IAP RNA. Intact gag, pol, or env open reading frames were not present in sequences of either family, although incomplete open reading frames spanning putative p27 and protease regions of IAP genes were observed.
Amino Acid Sequence↗
Effects of methotrexate on transfected DNA stability in mammalian cells.
The chromosomal locations, amounts, and level of expression of transfected, amplified c-myc and dihydrofolate reductase sequences were measured in cells cultured in the presence and absence of methotrexate. These studies show that the location and amount of transfected sequences, as well as the level of expression, were more variable when the cells were cultured in methotrexate.
Animals↗
Designing CD4 immunoadhesins for AIDS therapy.
A newly-constructed antibody-like molecule containing the gp120-binding domain of the receptor for human immunodeficiency virus blocks HIV-1 infection of T cells and monocytes. Its long plasma half-life, other antibody-like properties, and potential to block all HIV isolates, make it a good candidate for therapeutic use.
Acquired Immunodeficiency Syndrome↗
Use of fluorescence in situ hybridization to detect and monitor transfected and amplified sequences in recombinant CHO cells.
Non-radioactive fluorescence in situ hybridization was used to detect transfected and amplified sequences in recombinant CHO cells. The cell lines used in this study are based on DHFR-deficient CHO-DUKX cells. The recombinant CHO cells contain and express, as verified by Southern and Northern experiments, multiple copies of a constitutive DHFR expression vector, as well as an inducible Drosophila HSP 70 promoter-mouse c-myc construction. In order to localize and monitor the chromosomal location of transfected and amplified DHFR and c-myc sequences, biotinylated DNA probes were hybridized to metaphase preparations of several cell lines. The resulting hybrids were detected using fluorescein-linked avidin. The fluorescence signal was amplified using a biotinylated anti-avidin antibody. The number of c-myc and DHFR integration sites per metaphase, their distribution in cell populations growing at various methotrexate levels, the sizes of the amplified sequences, as well as the number of chromosomal rearrangements were measured. The results of this study will be presented and the usefulness of this method as a general tool for rapid characterization and monitoring of recombinant cell lines will be discussed.
Animals↗
Inducible overproduction of the mouse c-myc protein in mammalian cells.
We have made Chinese hamster ovary (CHO) cell lines that contain up to 2000 copies of the coding region of the mouse c-myc gene fused to the promoter of the Drosophila gene (hsp70) encoding a Mr 70,000 heat shock protein. Incubation of these cells at 43 degrees C results in an estimated 100-fold induction of c-myc mRNA. Translation of this mRNA occurs when the cells are returned to 37 degrees C, and during the first 3 hr of recovery at 37 degrees C, the c-myc protein is one of the most abundantly synthesized proteins in the cells. The products of the induced c-myc gene are phosphoproteins of apparent Mr 64,000, 66,000, and 75,000. Induced cells die, suggesting that elevated levels of c-myc are cytotoxic. Amplification of genes placed under control of the Drosophila hsp70 promoter may provide a general method for inducibly over expressing proteins in mammalian cells.
Animals↗