Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
 5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A plasmid containing the Escherichia coli chloramphenicol acetyltransferase (CAT) gene under the control of a mammalian cAMP-regulated promoter was entrapped in H-2Kk antibody-coated liposomes composed of dioleoyl phosphatidylethanolamine, cholesterol, and oleic acid (pH-sensitive immunoliposomes). The entrapped or free DNA was injected intraperitoneally into immunodeficient (nude) BALB/c mice bearing ascites tumor generated by H-2Kk-positive RDM-4 lymphoma cells. About 20% of the injected immunoliposomes were taken up by the target RDM-4 cells. Uptake was much less when liposomes without antibody were used. The presence of the targeting antibody on liposomes also significantly decreased the nonspecific uptake of liposomes by the spleen. Significant CAT enzyme activity was detected in RDM-4 cells from mice treated with DNA entrapped in the pH-sensitive immunoliposomes. Furthermore, CAT expression in RDM-4 cells was under the control of cAMP, as only the cells from mice injected with 8-bromo-cAMP and 3-isobutyl-1-methylxanthine showed CAT activity. CAT activity in liver and spleen was much lower (by factors of 12 and 5, respectively) than in the RDM-4 cells, and the activities in these reticuloendothelial organs were not regulated by cAMP. CAT activity in RDM-4 cells from mice injected with DNA entrapped in pH-insensitive immunoliposomes (containing phosphatidylcholine in place of phosphatidylethanolamine) was approximately one-fourth that in RDM-4 cells from mice injected with pH-sensitive immunoliposomes, indicating the superior delivery efficiency of the pH-sensitive liposomes. These results are discussed in terms of the DNA-carrier potential of immunoliposomes in therapy of cancer and genetic diseases.
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PMID:pH-sensitive immunoliposomes mediate target-cell-specific delivery and controlled expression of a foreign gene in mouse. 244 13

Primary human skin fibroblasts are an accessible source of phenotypically and karyotypically normal human cells, but are difficult to transfect with exogenous DNA. Here we demonstrate that both transient expression and stable transformation can be carried out by the method of electroporation. Highly efficient transient chloramphenicol acetyltransferase expression was shown after transfection with plasmid pRSVCAT. Stable transformation of human skin fibroblasts to G418 resistance was obtained after electroporation with neo-containing plasmids at an efficiency of approximately 1.4 x 10(-5)/micrograms DNA. The ability to easily transfect these cells with exogenous DNA may have important applications in the study of human genetic diseases and cancer.
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PMID:Transfection of primary human skin fibroblasts by electroporation. 285 91

Intrinsic and acquired multidrug resistance is an important problem in cancer therapy. Multidrug resistance results from overexpression of the MDR 1 gene, which encodes a drug-efflux pump called P-glycoprotein. We have isolated a 1-kilobase genomic fragment containing the major transcription initiation sites for the human MDR 1 gene. Ribonuclease protection experiments using this fragment indicate that normal human adrenal, colon, and liver cells, the human hepatoma cell line HepG2, and vinblastine-selected human KB multidrug-resistant cells initiate transcription of the MDR 1 gene at the same site within this fragment. The 0.43-kilobase region upstream from the major transcription initiation site linked to the chloramphenicol acetyltransferase gene showed promoter activity in CV-1 monkey kidney cells and in human KB cells. The putative promoter region has a consensus CAAT box and two GC box-like sequences, but no TATA sequence. This identification and isolation of promoter sequences for the MDR 1 gene will permit studies on how expression of this gene is regulated in normal human tissues and cancers.
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PMID:Isolation and sequence of the promoter region of the human multidrug-resistance (P-glycoprotein) gene. 289 92

Human T-cell leukemia virus type I has a unique sequence pX and the product p40x was proposed to be a specific trans-acting transcriptional activator of expression of the viral gene. Recently, a second pX protein p27x-III in addition to p40x was identified; these two proteins are encoded by overlapping frames III and IV (x-lor). For determination of which product is the trans-acting activator, site-directed mutations were introduced into the pX sequence which was placed under the metallothionein promoter. On cotransfection with pLTR-CAT (a plasmid containing the LTR of HTLV-I and chloramphenicol acetyltransferase gene), only the mutations that affected p40x expression inactivated the transcriptional activation from the LTR.
Jpn J Cancer Res 1985 Dec
PMID:The p40x of human T-cell leukemia virus type I is a trans-acting activator of viral gene transcription. 300 3

We constructed a fusion plasmid, pMX-I, by which the major open reading frame, X-I, of the bovine leukemia virus (BLV) X gene was expressed under control of the mouse metallothionein promoter. pMX-I was cotransfected into CV1 monkey kidney cells together with another construct containing the BLV long terminal repeat (LTR) linked to the chloramphenicol acetyltransferase (CAT) structural gene. The result of assay of CAT synthesis suggests that the X-I product functions as a trans-acting activation factor of the BLV LTR.
Jpn J Cancer Res 1987 Feb
PMID:The bovine leukemia virus X region encodes a trans-activator of its long terminal repeat. 303 Sep 87

The involvement of c-myc in the genesis of animal neoplasia is now well documented for several systems. In order to define the precise role played by the myc gene in tumorigenesis, a better understanding of the normal regulation of myc expression is necessary. We have begun a study of the cis-acting regulatory sequences within the 5' flanking domain of the human c-myc gene. Regions important for myc promoter function have been identified by linkage to the coding sequences of the bacterial chloramphenicol acetyltransferase (cat) gene. Promoter deletion studies and in vivo competition assays for c-myc/cat recombinant plasmids have allowed the identification of a proximal 'core' promoter region capable of directing high levels of CAT activity. Further upstream a negative regulatory element (NRE2) has been identified which is capable of repressing cat gene expression and which functions by interaction with a transacting factor(s). Preliminary data suggests detection of NRE2 is dependent on both the type and amount of carrier DNA used in transient CAT assays. Initial experiments further indicate the involvement of at least two other distal regulatory domains, a negative regulatory domain (NRE1) and a putative enhancer-type region (E). In vitro footprint analysis has allowed the identification of DNA binding proteins which interact with NRE2 and the 'core' promoter. NRE2 contains binding sites for transcription factors Sp1 and CTF. The 'core' promoter domain appears to be highly complex and possesses several Sp1 binding sites.
Br J Cancer Suppl 1988 Dec
PMID:Transcriptional regulation of the human c-myc gene. 307 67

As an alternative to directing plant or bacterial toxins to surface receptors, we are investigating the possibility of killing tumor cells by the expression of an exogenously introduced toxin gene (i.e., cell suicide). Tissue-specific gene regulatory elements might thus be exploited to achieve selective killing. To assess the feasibility of such an approach, we have transfected human cells (HeLa, B-lymphoblastoid, and 293 cells) with plasmids containing the diphtheria toxin A-chain (DT-A) coding sequence. The presence of the DT-A sequence lowered the level of transient expression of chloramphenicol acetyltransferase from a cotransfected plasmid, pSV2cat. This expression level in B-cells was further diminished by the inclusion of an immunoglobulin enhancer in the DT-A plasmid. In cotransfection experiments with a DT-A plasmid lacking an enhancer, chloramphenicol acetyltransferase expression was much more strongly inhibited in 293 cells (which express adenovirus E1A and E1B products) than in the other cell types; furthermore, the presence of the DT-A sequence eliminated recovery of G418-resistant 293 cell transformants after transfection with a plasmid containing the neo selectable marker. These results suggest that cell-specific regulatory mechanisms can be exploited to achieve selective cell killing by expression of an introduced toxin gene.
Cancer Res 1986 Sep
PMID:Regulated expression of a diphtheria toxin A-chain gene transfected into human cells: possible strategy for inducing cancer cell suicide. 346 Jun 97

In this paper we report both transient and stable complementation of pyrimidine dimer repair in xeroderma pigmentosum cells by the denV gene of bacteriophage T4, coding for endonuclease V, a dimer-specific DNA glycosylase. Cotransfection with pRSVdenV in SV40-transformed XP12RO(M1) cells (complementation group A) restored transient expression of an indicator plasmid (pRSVcat) bearing a UV-inactivated chloramphenicol acetyltransferase (cat) gene. In addition, XP12RO(M1) clones stably transformed by pRSVdenV-SVgpt expressed transient chloramphenicol acetyltransferase activity when transfected with UV-inactivated pRSVcat plasmid. These clones also showed partial restoration of colony forming ability and excision repair synthesis after UV irradiation. Immunofluorescence, using an endonuclease V polyclonal antibody, showed the presence of the phage glycosylase in stably transformed xeroderma pigmentosum cells. The cotransfection assay affords a rapid, sensitive procedure to screen for functional cloned DNA repair genes and to test mutant cells for the deficiency of specific steps in DNA repair, such as incision.
Cancer Res 1987 Jun 01
PMID:Transient and stable complementation of ultraviolet repair in xeroderma pigmentosum cells by the denV gene of bacteriophage T4. 356 13

The c-kit proto-oncogene encodes a tyrosine kinase receptor for stem cell factor and plays a critical role in the growth and differentiation of various types of cells including hematopoietic stem cells. To investigate the mechanisms of its transcriptional regulation, we isolated the 5' flanking region of the human c-kit gene and characterized its promoter activity in hematopoietic cells. Nucleotide sequence analysis revealed that the 1.2 kb 5' flanking region lacked a typical "TATA box," but had a relatively high G + C content and four potential Sp1-binding sites. Putative binding sites for AP-2, basic helix-loop-helix proteins, Ets-domain proteins, Myb and GATA-1 were also found. Primer extension and S1 nuclease protection analyses of hematopoietic cells indicated that the major transcription start sites are 62 bp and 58 bp upstream of the translation start site. Essentially the same start sites were detected in non-hematopoietic cells such as small cell lung carcinoma and glioblastoma: this single promoter in c-kit is different from the multiple promoter system of c-fms, a c-kit-related gene, in which at least two promoters are differently used in hematopoietic and non-hematopoietic cells. An analysis of the c-kit 5' flanking region using the bacterial chloramphenicol acetyltransferase gene (CAT assay) in human erythroleukemia HEL cells, which express the endogenous c-kit mRNA at high levels, showed that a region from -180 to -22 is important for the expression of the c-kit gene. In addition, a negative regulatory element(s) is suggested to be involved in the regulation of the c-kit gene expression in mammals.
Jpn J Cancer Res 1993 Nov
PMID:Characterization of the promoter region of the human c-kit proto-oncogene. 750 48

Proliferation of LNCaP 104-S cells, a clonal subline of the human prostate cancer cell line, was very slow in androgen-depleted medium but increased 10-13-fold in the presence of 0.1 nM of a synthetic androgen, R1881. This induction of proliferation was diminished at higher concentrations of R1881, indicating the biphasic nature of the androgen effect. After 20-30 passages in androgen-depleted medium, these cells progressed to 104-I cells, which exhibited much lower proliferative sensitivity to 0.1 nM R1881. After another 20-30 passages, LNCaP 104-I cells gave rise to 104-R cells, which proliferated rapidly without additional androgen. Proliferation of 104-R cells was induced 2-fold by 0.01 nM R1881 but was repressed by 0.1 nM R1881 and above. Thus, androgen induction and repression of proliferation could be seen at lower concentrations of androgen as the cells progressed. During the transition of 104-S cells to 104-R cells, the androgen receptor mRNA level increased 2.5-fold whereas the androgen receptor protein level increased 15-fold in the absence of androgen. Androgen receptor transcriptional activity, measured by androgen induction of prostate-specific antigen mRNA and chloramphenicol acetyltransferase activity in transfected cells, increased up to 20-fold during the progression. LNCaP cells, therefore, appear to be able to adapt to reduced androgen availability by increasing their sensitivity to androgen, raising questions concerning the therapeutic strategies used against prostate cancer. Androgen induction of c-myc expression in 104-R cells occurred at a 10-fold lower concentration (0.01 nM) than in 104-S cells (0.1 nM). In all stages, cell proliferation and c-myc expression were repressed by androgen at a high concentration (20 nM), but the repression of cell proliferation was blocked by retroviral overexpression of c-myc.
Cancer Res 1994 Mar 15
PMID:Increased androgen receptor activity and altered c-myc expression in prostate cancer cells after long-term androgen deprivation. 751 Oct 45


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