Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.3.1.28 (chloramphenicol acetyltransferase)
5,100 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We used the Escherichia coli chloramphenicol acetyltransferase gene (cat) to study sequences that influence expression of the equine infectious anemia virus (EIAV) genome. The EIAV long terminal repeat (LTR) directed CAT activity in a canine cell line, but at levels much lower than those achieved with other eucaryotic viral promoters. In the same cells infected with EIAV or cotransfected with molecularly cloned EIAV genomic DNA, LTR-directed activity was markedly enhanced. Comparison of cat mRNA and protein levels in these cells indicated that this trans-activating effect could be accounted for by a bimodal mechanism in which both transcriptional and posttranscriptional events are enhanced. trans-Activation but not promoter activity was abolished by deletion of the R-U5 region of the EIAV LTR. EIAV sequences responsible for the trans-activating function could be localized to a region encompassing the 3' and 5' termini of the pol and env genes, respectively (nucleotides 4474 to 5775). Interestingly, this stretch harbors a short open reading frame with some amino acid sequence similarity to the human immunodeficiency virus type I tat gene product.
...
PMID:Localization of sequences responsible for trans-activation of the equine infectious anemia virus long terminal repeat. 282 40

Almost all homosexual patients with acquired immunodeficiency syndrome are also actively infected with human cytomegalovirus (HCMV). We have hypothesized that an interaction between HCMV and human immunodeficiency virus (HIV), the agent that causes acquired immunodeficiency syndrome, may exist at a molecular level and contribute to the manifestations of HIV infection. In this report, we demonstrate that the immediate-early gene region of HCMV, in particular immediate-early region 2, trans-activates the expression of the bacterial gene chloramphenicol acetyltransferase that is fused to the HIV long terminal repeat and carried by plasmid pHIV-CAT. The HCMV immediate-early trans-activator increases the level of mRNA from the plasmid pHIV-CAT. The sequences of HIV that are responsive to trans-activation by the HCMV immediate-early region are distinct from HIV sequences that required for response to the HIV tat. The stimulation of HIV gene expression by HCMV gene functions could enhance the consequences of HIV infection in persons with previous or concurrent HCMV infection.
...
PMID:Immediate-early gene region of human cytomegalovirus trans-activates the promoter of human immunodeficiency virus. 282 1

A Sal I-Xho I fragment containing the genes encoding tat, art, and the envelope proteins from the BH10 clone of human immunodeficiency virus (HIV) was inserted into a simian virus 40 (SV40)-based eukaryotic expression vector. The vector is a shuttle vector that replicates to high copy numbers in both Escherichia coli and eukaryotic cells permissive for SV40 replication. Transfection of the HIV DNA-containing vector (pSVSX1) into the CV-1 monkey cell line gave high levels of expression of the envelope glycoproteins gp160 and gp120 in 20-30% of the transfected cells. By several criteria, the proteins were indistinguishable from those produced during infection. The proteins were localized to the cytoplasm and plasma membrane, and some of the gp120 was shed into the culture medium. Approximately 0.5 microgram of envelope protein could be extracted from 10(6) cells. This is at least 100 times higher than the levels found in HIV-infected H9 cells. In addition, a trans-activation assay performed with pSVSX1 and a plasmid containing the gene for chloramphenicol acetyltransferase under the control of the HIV long terminal repeat demonstrated that a functional tat gene product also was expressed. Thus, this transient vector system provides an abundant source of native envelope protein for purification and characterization and also will be useful for studies dealing with the regulation of HIV gene expression.
...
PMID:Coexpression of human immunodeficiency virus envelope proteins and tat from a single simian virus 40 late replacement vector. 282 81

Acquired immunodeficiency syndrome patients are frequently coinfected with Epstein-Barr virus (EBV). In this report, we demonstrate that an EBV immediate-early gene product, BamHI MLF1, stimulates expression of the bacterial chloramphenicol acetyltransferase (CAT) gene linked to the human immunodeficiency virus (HIV) promoter. The HIV promoter sequences necessary for trans-activation by EBV do not include the tat-responsive sequences. In addition, in contrast to the other herpesvirus trans-activators previously studied, the EBV BamHI MLF1 gene product appears to function in part by a posttranscriptional mechanism, since it increases pHIV-CAT protein activity more than it increases HIV-CAT mRNA. This ability of an EBV gene product to activate HIV gene expression may have biologic consequences in persons coinfected with both viruses.
...
PMID:An Epstein-Barr virus immediate-early gene product trans-activates gene expression from the human immunodeficiency virus long terminal repeat. 283 Jun 25

Human immunodeficiency virus-1 (HIV-1), which causes AIDS (acquired immune deficiency syndrome), possesses an essential gene, tat, whose product, acting through the long terminal repeat (LTR) sequences of HIV-1, activates viral genes and replication. The mechanism by which tat trans-activates HIV genes is unclear. Some studies have reported that an increase in messenger RNA accumulation directed by the HIV-1 LTR can explain the action of tat, but others suggest that this increase in mRNA levels can only partially explain trans-activation, and that translational control mechanisms may also be involved. To test those possibilities we have established an efficient adenovirus system for delivering the HIV-1 LTR attached to a reporter gene (chloramphenicol acetyltransferase; CAT) into cells and monitoring its activity. The HIV-1 LTR expressed from this adenovirus responds to trans-activation in a HeLa cell line constitutively expressing the tat protein by increasing the transcription rate of the HIV-1 LTR and the accumulation of mRNA encoding CAT. In this system the translational efficiency of this CAT mRNA in the cell is unaffected by the presence of tat.
...
PMID:Transcriptional but not translational regulation of HIV-1 by the tat gene product. 283 3

The tat gene of the human immunodeficiency virus, tat-III, when introduced into T-lymphoblastoid Jurkat cells by a Moloney retroviral recombinant DNA vector expressed high levels of the functional tat protein as measured by the chloramphenicol acetyltransferase assay. Immunofluorescence analysis with CD4-specific monoclonal antibodies demonstrated that the cell surface levels of the CD4 antigen were increased by 5- to 10-fold in the tat-III-infected Jurkat cells. Cellular cytoplasmic RNA analysis indicated that the enhanced CD4 expression was mediated at the mRNA level. Our findings suggest that the single expression of the human immunodeficiency virus tat protein in the absence of the other viral proteins causes an upregulation of CD4 gene expression on helper T cells, although infection of these cells by the virus, thus expressing all the viral gene products including tat, is known to downregulate CD4 antigen expression.
...
PMID:Increased expression of CD4 molecules on Jurkat cells mediated by human immunodeficiency virus tat protein. 284 47

The genomes of human retroviruses [human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus (HTLV-I)] encode positive trans-activator proteins, named tat. In the presence of tat, the transcriptional activity of the homologous HIV-1 or HTLV-I long terminal repeat (LTR) promoter is markedly increased. We have constructed mammalian cell lines that contain stably integrated copies of a HIV-1 or a HTLV-I LTR-chloramphenicol acetyltransferase (CAT) gene. When presynthesized HIV-1 or HTLV-I tat proteins were separately introduced into these cells in the presence of cycloheximide, we found a strong increase in the steady-state expression of the homologous viral LTR. Nuclear "run-on" assays verified that this tat-mediated enhancement, occurring in the absence of de novo cellular protein synthesis, was due to increased transcriptional initiation at the LTR promoter. We conclude that one aspect of transcriptional trans-activation of viral LTR by the HIV-1 and HTLV-I tat proteins does not require the production of new cellular proteins.
...
PMID:Transcriptional activation of homologous viral long terminal repeats by the human immunodeficiency virus type 1 or the human T-cell leukemia virus type I tat proteins occurs in the absence of de novo protein synthesis. 284 57

Cotransfection of cDNA encoding the trans-activator gene product of human T-cell leukemia virus, type I (HTLV-I) (tat-I), which acts in trans to augment viral gene expression, has revealed strong regulatory effects of this viral protein on the inducible cellular promoters governing human interleukin 2 (IL-2) and IL-2 receptor (Tac) gene expression. The tat-I protein stimulates a 3- to 6-fold increase in IL-2 receptor (Tac) promoter activity in transfected Jurkat T cells, but not in the natural killer-like YT cell line, as measured by changes in the expression of the chloramphenicol acetyltransferase (CAT; EC 2.3.1.28) reporter gene linked to this promoter. In contrast, tat-I alone has little or no effect on IL-2 promoter activity in Jurkat T cells but markedly synergizes with other mitogenic stimuli (phytohemagglutinin, phorbol 12-myristate 13-acetate, or the OKT3 monoclonal antibody), which alone are ineffective. The tat-I protein also partially circumvents the pronounced inhibitory effects of cyclosporin A on the IL-2 promoter. Other cellular and viral promoters are unaffected by the tat-I gene product, either alone or in combination with other mitogens. The specific effects of the tat-I gene product on the IL-2 and IL-2 receptor (Tac) promoters suggest the possibility of an autocrine or paracrine mechanism of T-cell growth as an early event in HTLV-I-mediated leukemogenesis.
...
PMID:Activation of interleukin 2 and interleukin 2 receptor (Tac) promoter expression by the trans-activator (tat) gene product of human T-cell leukemia virus, type I. 303 48

D-Penicillamine, an amino acid analogue of cysteine, has been shown to inhibit the transactivation of HIV-1 LTR by the transactivator protein, tat protein. The transactivation was studied in Jurkat cells co-transfected with plasmids containing HIV-LTR sequences fused to the bacterial chloramphenicol acetyltransferase (CAT) gene and HIV tat gene. The expression of CAT activity was a measure of transactivation of LTR by the tat protein. Incubation of transfected Jurkat cells with D-penicillamine led to inhibition of CAT activity. This inhibition was found to be concentration-dependent; more than 90% inhibition of chloramphenicol acetylation was seen in extracts prepared from cultures incubated with 40 micrograms/ml of D-penicillamine. Earlier experiments have shown that D-penicillamine at 40 micrograms/ml can completely inhibit HIV-1 (HTLV-III B) replication in H9 cells [(1986) Drug Res. 36, 184-186]. These results suggest that inhibition of transactivation may be the molecular mechanism involved in the inhibition of HIV-1 replication by D-penicillamine.
...
PMID:D-penicillamine inhibits transactivation of human immunodeficiency virus type-1 (HIV-1) LTR by transactivator protein. 341 42

Several retroviruses encode trans-acting factors which activate gene expression directed by long terminal repeat (LTR) sequences and play a role in the positive feedback regulation of virus replication. We have examined two Mason-Pfizer monkey virus (MPMV) strains for their ability to produce and respond to such factors. Plasmids with the LTR of either MPMV or type D retrovirus/New England (D/NE) were fused to the bacterial chloramphenicol acetyltransferase (CAT) gene. Introduction of these plasmids into several different human cell lines gave rise to significant CAT activity, demonstrating the strong transcriptional promoter activity of these LTRs. However, little or no increase in CAT activity was found upon transfection of these plasmids into MPMV- or D/NE-infected cell lines as compared with uninfected cell lines. Furthermore, CAT activity was not enhanced in uninfected cells by cotransfecting either a functional MPMV DNA clone, a plasmid expressing the human T-lymphotropic retrovirus trans-activator genes, tat-1 or tat-3. These data show that the property of trans-activation of LTR-mediated gene expression is a function in the replication of only certain retroviruses.
...
PMID:Trans-activation of long terminal repeat sequence-mediated gene expression is not a property of type D retrovirus replication. 361 91


<< Previous 1 2 3 4 5 6 7 Next >>

---