Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.5.1.3 (dihydrofolate reductase)
 5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rous sarcoma virus(RSV)-transformed Chinese hamster fibroblasts, containing approximately ten copies of the DNA domain comprising a single provirus and its flanking cellular sequences, were arrested in metaphase, and the chromosomes were fractionated by size in a sucrose gradient. The resolution of polymorphic ribosomal genes, the dihydrofolate reductase gene, and the c-src gene demonstrated that the gradient can distinguish between small, medium, and large chromosomes. The same DNA domain carrying the RSV provirus was found to be associated with chromosomes of all three size classes. Polymorphic copies of the domain in small and large chromosomes could be distinguished from those in medium-sized chromosomes because of the polymorphism in the XhoI and EcoRI sites on 5' and 3' adjacent cellular sequences, respectively. The presence of the same provirus domain on different chromosomes, together with the karyological data showing trisomies in the same chromosome size classes, suggest that the provirus domain, possibly the entire replicon, was duplicated and transferred to different nonhomologous chromosomes, and the transfer was followed by duplication of the target chromosomes. The possibility that proviral long terminal repeats might be involved in replicon transfer is discussed.
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PMID:RSV provirus with same flanking sequences is found on different size classes of Chinese hamster chromosomes. 298 58

Expression plasmids containing human interleukin-2(IL-2) cDNA under the control of viral promoters (SV40 early region, MuLV LTR, HTLV-I LTR, and ASV (Y73) LTR) were introduced into TK- mouse L cells and human FL cells to establish IL-2 producing cells. The highest levels of IL-2 producing clones were obtained in TK+ mouse L cells transformed with a recombinant plasmid having MuLV LTR as a promoter, whereas transformed cells of human FL cells (G418r) were revealed to produce IL-2 at the highest level when the cells were transfected with a plasmid containing HTLV LTR as a promoter. These results suggest that these promoter/enhancer regions possess different cell specificities in gene expression. To obtain higher levels of IL-2 production using gene amplification, the hybrid plasmids containing the hamster DHFR and human IL-2 genes were constructed and transfected into DHFR- CHO cells. DHFR+ colonies produced IL-2 at about the same level as that produced by TK+ L cells transformed with the recombinants containing MuLV LTR. Selection of methotrexate-resistant cells resulted in a 5- to 30-fold increase of IL-2 production. These cells produced IL-2 stably for at least 3 months, even in the absence of methotrexate.
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PMID:The establishment of IL-2 producing cells by genetic engineering. 303 77