Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:EXPT01586 (G418)
 2,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A differentiation-defective variant (DD-1) of the MM14 myoblasts acquired the ability to synthesize DNA in response to treatment with epidermal growth factor (EGF) (R. W. Lim and S. D. Hauschka, 1984, Dev. Biol. 105, 48) and no longer expressed myogenic determinant genes (i.e., MyoD and myogenin) (P.R. Mueller, and B. Wold, 1989, Science 246, 780). To determine the effect of expression of MyoD on EGF responsiveness, DD-1 cells were cotransfected with a MyoD expression vector and with pRSVneo. A clone, MyoDD-1 cells, which was G418 resistant, formed multinuclear syncitia, and also expressed MyoD and myogenin, was further characterized. EGF responsiveness, as assessed by DNA synthesis, was decreased 5- to 10-fold in the MyoDD-1 cells from that in G418-resistant control DD-1 cells, despite similar EGF receptor numbers and binding affinities of the receptors. Responsiveness of MyoDD-1 cells to fibroblast growth factor (FGF) was also diminished although to a lesser extent. To determine the effects of decreased myogenic determinant gene expression on mitogen responsiveness, MM14 myoblasts were grown in medium supplemented with 5 microM 5-bromo-2'-deoxyuridine (BUdR-MM14). BUdR-MM14 cells had decreased expression of MyoD and myogenin, did not fuse, and had an altered morphology, from round to flat. The BUdR effect on fusion and cell shape was reversed by growth in control medium. BUdR-MM14 cells were responsive to EGF and had enhanced responsiveness to FGF. The combined studies support the view that expression of MyoD and/or myogenin contributes to negative regulation of mitogen responsiveness.
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PMID:Growth factor responsiveness: role of MyoD and myogenin. 132 43

The replication of a simian virus 40 (SV40) origin-containing plasmid, pSLneo, stably transfected COS7 cells has been studied. pSLneo contains the SV40 origin of replication and encodes the positive selectable marker for G418 resistance. In transient replication assays, pSLneo replicates to a high copy number in COS7 cells. Uncontrolled SV40 plasmid replication has been reported to be lethal to such transfected cells. Thus, it was anticipated that extensive plasmid replication would preclude isolation of permanent cell lines containing pSLneo. However, significant number of G418-resistant colonies arose after transfection of COS7 cells with pSLneo. Cell lines established from these drug-resistant colonies contained between 100 and 1,000 extrachromosomal pSLneo copies per cell. Episomal plasmid DNA in pSLneo/COS7 lines was stably maintained after 2 months of continuous culture in selective medium. Bromodeoxyuridine labeling and density shift experiments demonstrated that replication of pSLneo closely paralleled that of cellular DNA. On average, plasmid DNA did not replicate more than once during a single cell generation period. Regulation of pSLneo replication appeared to be negatively controlled by a cis-acting mechanism. Endogenous copies of episomal pSLneo remained at a stable low copy number during the simultaneous, high-level replication of a newly transfected plasmid encoding SV40 large T antigen in the same cells. These results indicate that regulated replication of an SV40 origin plasmid can be acquired in a cell and does not require the presence of additional genetic elements. The molecular mechanism by which cells enforce this regulation on extrachromosomal SV40 plasmids remains to be defined.
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PMID:Regulated replication of an episomal simian virus 40 origin plasmid in COS7 cells. 165 81

Recombinant vaccinia virus is a useful and powerful tool for the expression and study of foreign genes. Methods that are currently available for the selection of vaccinia virus recombinants include the restoration of viral plaque-forming phenotype, the replication of viral DNA in the presence of BUdR or mycophenolic acid, and the maturation and propagation of virus under antibiotic selection. Though effective, each of these methods requires several weeks of concerted effort to isolate, purify, and amplify a potential recombinant virus. Here we report the development of a bifunctional enzyme (BiZyme) to simplify and expedite the isolation and purification of vaccinia virus recombinants. This novel selection marker is composed of an in-frame fusion between the genes encoding gfp and the neomycin phosphotransferase enzyme (neo). Remarkably, expression of the chimeric gfp-neo cassette in the presence of G418 confers both viability and fluorescence to transfected or recombinant virus-infected cells, indicating that both activities are retained within the fusion protein. Therfore, BiZyme was incorporated into a recombination plasmid (pGNR) to enable the concomitant insertion of a foreign gene of interest. Here we demonstrate that this selection/amplification process requires a minimum of 11 days to produce the desired vaccinia virus recombinants. Furthermore, recombinants produced in this fashion have been shown to express both biologically active enzymes and antigenically authenticforeign antigens. In addition to its use in the vaccinia virus vector system, the BiZyme bifunctional selection scheme should be applicable to other eukaryotic and prokaryotic expression systems, simply by coupling it to the appropriate host-specific transcription regulatory signals.
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PMID:BiZyme: a novel fusion protein-mediating selection of vaccinia virus recombinants by fluorescence and antibiotic resistance. 1201 92