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

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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)

The A20 gene product is a novel zinc finger protein originally described as a tumor necrosis factor alpha (TNF)-inducible early response gene in human umbilical vein endothelial cells (HUVEC). Its described function is to block TNF-induced apoptosis in fibroblasts and B lymphocytes, but more recently it has also been shown to play a role in lymphoid cell maturation. The mechanism of action of A20 is unknown. The aim of our study was to assess the effect of A20 upon endothelial cell activation. By transfecting bovine aortic endothelial cells (BAEC) with A20 as well as reporter constructs consisting of the promoters of genes known to be up-regulated during endothelial cell activation, i.e. E-selectin, interleukin (IL)-8, tissue factor (TF), and inhibitor of nuclear factor kappaBalpha (IkappaBalpha), we demonstrate that A20 expression inhibits gene up-regulation associated with TNF, lipopolysaccharide (LPS), phorbol 12-myristate 13-acetate (PMA), and hydrogen peroxide (H2O2)-induced endothelial cell (EC) activation. The mechanism of action of A20 is in part, or totally, due to the blockade of nuclear factor kappaB (NF-kappaB), as shown by its ability to suppress the activity of a NF-kappaB reporter. This effect is specific, as A20 does not block a noninducible, constitutively expressed reporter, Rous sarcoma virus-luciferase (RSV-LUC); nor does it block the c-Tat-inducible, NF-kappaB-independent reporter, human immunodeficiency virus-chloramphenicol acetyltransferase (HIV-CAT). How A20 blocks NF-kappaB is unclear, although we demonstrate that it does not affect p65 (RelA)-mediated gene transactivation. The inhibition of endothelial cell activation by A20 is a novel function for A20.
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PMID:A20 blocks endothelial cell activation through a NF-kappaB-dependent mechanism. 866 99

Human lymphoid cell lines were transfected with HIV-1-LTR-CAT DNA and permanently transformed cell lines were obtained. These transformed cell lines were treated with 0.01 mM H2O2 for 25 days and the chloramphenicol acetyltransferase (CAT) activities of these cell lines were measured. The CAT activities of transformed cell lines were latent in normal culture conditions, but were activated by retreatment with 0.2 mM H2O2 for 1 h. On treatment with 0.05 mM H2O2 for 1 h, the CAT activity of these cell lines maintained in normal conditions remained latent, whereas cell lines pretreated with 0.01 mM H2O2 for 25 days were greatly activated by this treatment. Here, the HIV-1 promoter seemed latent in normal culture conditions, but it could be activated by a comparatively low concentration (0.05 mM) of H2O2 after treatment with a dilute H2O2 (0.01 mM) for about 1 month. Many patients infected with human immunodeficiency virus 1 (HIV-1) show a long latent period before development of AIDS. During this latent period, their infected cells may be subjected to oxidative stress due to metabolism and physical movement. The present results indicate that oxidative stress may cause activation of the HIV-1 promoter in patients with latent HIV-1.
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PMID:Sensitization of the HIV-1-LTR upon long term low dose oxidative stress. 870 77

Membrane lymphotoxin (LT) complex is a trimer composed of two subunits , LT-alpha and LT-beta of which the latter is a 33-kDa transmembrane protein. The LT-beta gene is expressed in lymphoid cells and organs, but little is known about its inducible regulation. Previously, the surface expression of LT-beta in Jurkat cells has been shown to increase in response to PMA. In this report, we used this model to study the transcriptional control of the human and murine LT-beta genes. PMA strongly induced the expression of LT-beta mRNA, and the level of induction was not changed markedly by cycloheximide (CHX) treatment. The LT-beta promoter region contains conserved Egr-1, nuclear factor (NF)-kappaB, and Ets binding sites, and PMA-inducible factors bound to these sites were detected by the gel-retardation technique (electrophoretic mobility shift assay (EMSA)). To identify sequences involved in transcriptional control, sets of human and mouse promoter-chloramphenicol acetyltransferase (CAT) constructs were generated and assayed by transient transfections. The PMA response was lost after deletion of the distal Ets binding site at -110. Mutations at either the Ets or NF-kappaB sites that prevented factor binding dramatically reduced PMA-inducible promoter activity, suggesting cooperative interaction between corresponding transcription factors in PMA activation. Mutation at the Egr-1 site also resulted in substantial loss of promoter activity, and the residual activity may be attributed to binding of constitutively expressed Sp-1 to the same site. We propose that the interaction between the members of NF-kappaB and Ets families of transcription factors and their cognate sites in the promoter is the major determinant of inducible expression of the LT-beta gene in Jurkat cells.
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PMID:Functional analysis of the lymphotoxin-beta promoter. Sequence requirements for PMA activation. 878 6

The ability of glucocorticoids (GCs) to induce death in lymphoid-origin cells is the basis for their frequent use in the therapy of various human hematological malignancies. However, the occurrence of primary or secondary GC resistance limits their clinical usefulness. Prior investigations into the mechanism of GC resistance in established human leukemic cell lines revealed loss-of-function mutations in the GC receptor (GR) gene. In this study, we analyzed the GC-resistant human acute T-cell leukemia line CEM-C1, which has been reported to express biochemically functional GR and, thus, was thought to owe its GC resistance to signal transduction changes distal from the GR. Radioligand binding assays revealed a 2-3-fold lower expression of GR in CEM-C1 than in the GC-sensitive sister cell line CEM-C7H2. Analysis of transcriptional activity using mouse mammary tumor virus-long terminal repeat-controlled chloramphenicol acetyltransferase expression in transient transfection assays confirmed the expression of functional GR in CEM-C1 but at levels lower than those in CEM-C7H2 cells. Upon molecular analyses of the GR gene and its transcripts, we found that CEM-C1 cells were heterozygous for the ligand binding domain L753F point mutation in exon 9, which is also present in GC-sensitive CEM-C7H2. No mutations, however, were found on the second GR allele of CEM-C1. To test the possibility that resistance in CEM-C1 cells might be caused by insufficient expression of GR, we established several cell lines stably transfected with rat GR expression vectors. These cell lines differed in exogenous GR expression as determined by Northern blotting and radioligand binding assays. The GR expression level in individual lines correlated well with their sensitivity to GC-induced apoptosis. Thus, GC resistance of CEM-C1 cells might be due to subthreshold expression of functional GR rather than defects in signal transduction pathways distal from the GR. Since several clinical investigations showed a correlation between reduced GR expression and poor response to GC-containing treatment, the CEM-C1 line may represent a valid model for GC resistance in human acute T-cell leukemia.
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PMID:Resistance to glucocorticoid-induced apoptosis in human T-cell acute lymphoblastic leukemia CEM-C1 cells is due to insufficient glucocorticoid receptor expression. 889 60

Cytomegalovirus (CMV) infection is nonpermissive or persistent in many lymphoid and myeloid cell types but can be activated in differentiated macrophages. We have shown elsewhere that both the major immediate-early gene (MIE) and lytic cycle infectious progeny virus expression can be induced in otherwise nonpermissive monocyte-like U-937 cell cultures infected with either human CMV (HCMV) or simian CMV (SCMV) by treatment with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Two multicopy basal enhancer motifs within the SCMV MIE enhancer, namely, 11 copies of the 16-bp cyclic AMP response element (CRE) and 3 copies of novel 17-bp serum response factor (SRF) binding sites referred to as the SNE (SRF/NFkappaB-like element), as well as four classical NFkappaB sites within the HCMV version, contribute to TPA responsiveness in transient assays in monocyte and T-cell types. The SCMV SNE sites contain potential overlapping core recognition binding motifs for SRF, Rel/NFkappaB, ETS, and YY1 class transcription factors but fail to respond to either serum or tumor necrosis factor alpha. Therefore, to evaluate the mechanism of TPA responsiveness of the SNE motifs and of a related 16-bp SEE (SRF/ETS element) motif found in the HCMV and chimpanzee CMV MIE enhancers, we have examined the functional responses and protein binding properties of multimerized wild-type and mutant elements added upstream to the SCMV MIE or simian virus 40 minimal promoter regions in the U-937, K-562, HL-60, THP-1, and Jurkat cell lines. Unlike classical NFkappaB sites, neither the SNE nor the SEE motif responded to phosphatase inhibition by okadaic acid. However, the TPA responsiveness of both CMV elements proved to involve synergistic interactions between the core SRF binding site (CCATATATGG) and the adjacent inverted ETS binding motifs (TTCC), which correlated directly with formation of a bound tripartite complex containing both the cellular SRF and ELK-1 proteins. This protein complex was more abundant in U-937, K-562, and HeLa cell extracts than in Raji, HF, BALB/c 3T3, or HL-60 cells, but the binding activity was altered only twofold after TPA treatment. A 40-fold stimulation of chloramphenicol acetyltransferase activity mediated by four tandem repeats of the SNE could be induced within 2 h (and up to 250-fold within 6 h) after addition of TPA in DNA-transfected U-937 cells, indicating that the stimulation appeared likely to be a true protein kinase C-mediated signal transduction event rather than a differentiation response. Slight differences in the sequence of the core SRF binding site compared with that of the classical c-Fos promoter serum response element, together with differences in the spacing between the SRF and ETS motifs, appear to account for the inability of the SCMV SNEs to respond to serum induction.
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PMID:Synergistic interactions between overlapping binding sites for the serum response factor and ELK-1 proteins mediate both basal enhancement and phorbol ester responsiveness of primate cytomegalovirus major immediate-early promoters in monocyte and T-lymphocyte cell types. 897 Sep 84

The present study reports the exon-intron organization of the human RI alpha gene of cAMP-dependent protein kinase and approximately kilobases (kb) of the 5'-flanking region obtained by isolation and sequencing of several phage clones from human genomic libraries. The RI alpha gene is composed of nine coding exons of varying lengths, separated by introns, giving the gene a total length of at least 21 kb. our recent cloning of a processed RI alpha pseudogene with a 5'-noncoding region different from the previously reported RI alpha complementary RNA indicated that the RI alpha gene may have multiple leader exons giving rise to alternately spliced messenger RNAs (mRNAs). Reverse transcription of human testis RNA followed by PCR identified two different RI alpha mRNA species (RI alpha 1a and RI alpha 1b) containing distinct sequences due to alternately splicing the gene. The previously known RI alpha 1b mRNA revealed low constitutive expression in a human B lymphoid cell line (Reh) and was stimulated only 4- to 6-fold by treatment with cAMP. In contrast, very low levels of the novel RI alpha 1a mRNA were present in untreated Reh cells, but were stimulated 40-to 50-fold by cAMP. The 5'-flanking sequence of the RI alpha gene was G/C rich and did not contain any TATA box. Several putative transcription initiation sites were identified in front of each leader exon (exons 1a and 1b) by the 5'-rapid amplification of complementary DNA ends technique. To determine whether the sequences 5' of both leader exons had promoter activities, the 5'-flanking sequences of exons 1a and 1b were inserted in front of a chloramphenicol acetyltransferase reporter gene, and their ability to direct transcription were examined. Transfection of these constructs into rat GH4C1 cells demonstrated that both constructs had promoter activities, as evidenced by high levels of chloramphenicol acetyltransferase activity.
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PMID:The human gene for the regulatory subunit RI alpha of cyclic adenosine 3', 5'-monophosphate-dependent protein kinase: two distinct promoters provide differential regulation of alternately spliced messenger ribonucleic acids. 897 1

Repetitive structure of enhancer elements in the long terminal repeat (LTR) has been identified in feline leukemia viruses (FeLVs) integrated in lymphoid tumor cells in cats. In this study, promoter activities of the FeLV LTRs were measured in lymphoid and non-lymphoid cell lines in transient expression assays using plasmids containing the viral LTRs linked to the chloramphenicol acetyltransferase (CAT) gene. Promoter activity of the LTR with 3 enhancer repeats (pFTLTR) was significantly higher than that of the LTR with 1 enhancer (Glasgow-1 LTR) in feline (FT-1) and human (Jurkat) T-lymphoblastoid cell lines. Promoter activity of the pFTLTR was also significantly higher than that of its mutant (pFTLTR1E) in which 2 of the 3 enhancers were deleted in FT-1 and Jurkat cells. Both of these differences were not observed in a feline fibroblastic cell line (CrFK). Moreover, mutations affecting the consensus motifs for LVb, SV40, NF-1, GRE and FLV-1 resulted in decreased basal activity of the FeLV LTR (pFTLTR1E) in FT-1, Jurkat and CRFK cells. The decrease of the promoter activity was especially remarkable in FT-1 cells. The present study revealed the strong promoter activity of the FeLV LTR with 3 enhancer repeats and its modular enhancer elements positively regulating the transcription in a relatively tissue-specific manner.
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PMID:Regulation of gene expression directed by the long terminal repeats of feline leukemia viruses. 920 39

The nuclear matrix has been implicated in several cellular processes, including DNA replication, transcription, and RNA processing. In particular, transcriptional regulation is believed to be accomplished by binding of chromatin loops to the nuclear matrix and by the concentration of specific transcription factors near these matrix attachment regions (MARs). A number of MAR-binding proteins have been identified, but few have been directly linked to tissue-specific transcription. Recently, we have identified two cellular protein complexes (NBP and UBP) that bind to a region of the mouse mammary tumor virus (MMTV) long terminal repeat (LTR) previously shown to contain at least two negative regulatory elements (NREs) termed the promoter-proximal and promoter-distal NREs. These NREs are absent from MMTV strains that cause T-cell lymphomas instead of mammary carcinomas. We show here that NBP binds to a 22-bp sequence containing an imperfect inverted repeat in the promoter-proximal NRE. Previous data showed that a mutation (p924) within the inverted repeat elevated basal transcription from the MMTV promoter and destabilized the binding of NBP, but not UBP, to the proximal NRE. By using conventional and affinity methods to purify NBP from rat thymic nuclear extracts, we obtained a single major protein of 115 kDa that was identified by protease digestion and partial sequencing analysis as the nuclear matrix-binding protein special AT-rich sequence-binding protein 1 (SATB1). Antibody ablation, distamycin inhibition of binding, renaturation and competition experiments, and tissue distribution data all confirmed that the NBP complex contained SATB1. Similar types of experiments were used to show that the UBP complex contained the homeodomain protein Cux/CDP that binds the MAR of the intronic heavy-chain immunoglobulin enhancer. By using the p924 mutation within the MMTV LTR upstream of the chloramphenicol acetyltransferase gene, we generated two strains of transgenic mice that had a dramatic elevation of reporter gene expression in lymphoid tissues compared with reporter gene expression in mice expressing wild-type LTR constructs. Thus, the 924 mutation in the SATB1-binding site dramatically elevated MMTV transcription in lymphoid tissues. These results and the ability of the proximal NRE in the MMTV LTR to bind to the nuclear matrix clearly demonstrate the role of MAR-binding proteins in tissue-specific gene regulation and in MMTV-induced oncogenesis.
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PMID:The matrix attachment region-binding protein SATB1 participates in negative regulation of tissue-specific gene expression. 927 5

The LYT-10 gene was initially cloned by virtue of its disruption by the translocation breakpoint in some t(10;14) lymphoid neoplasms. LYT-10 is now known to encode a component of the NF-kappaB family of transcriptional activators and has therefore also been designated NFkappaB2. Activation of NF-kappaB is generally associated with its transfer to the nucleus and is followed by a rapid increase in expression of its target genes, which include cytokines such as interleukin-6 (IL-6). IL-6 can also be induced by other transcription factors such as NF-IL6. We studied the interaction of IL-1 and these transcription factors in two renal cell carcinoma cell lines (ACHN and Caki-1). These lines produce high levels of IL-6, show endogenous chloramphenicol acetyltransferase activity for the IL-6 promoter, and have high basal levels of transcripts encoding the NF-kappaB components Lyt-10, p50, and p65 as well as the NF-IL6 transcription factor. IL-1alpha and IL-1beta markedly increased steady-state levels of LYT-10 (NFkappaB2) transcripts and nuclear Lyt-10 protein in both cell lines. Levels of the NFkappaB1 (p50-encoding), p65, and NF-IL6 transcripts also increased after IL-1 exposure. These changes were accompanied by a 20-fold or greater increase in levels of IL-6 messenger ribonucleic acid (mRNA) and protein. Our observations suggest that the mechanism by which IL-1alpha or IL-1beta induces IL-6 may be mediated through increases in LYT-10 mRNA and protein levels as well as increases in expression of other transcription factors (NFkappaB1, p65, and NF-IL6), in addition to the known ability of IL-1 to post-translationally activate NF-kappaB.
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PMID:Interleukin-1 increases expression of the LYT-10 (NFkappaB2) proto-oncogene/transcription factor in renal cell carcinoma lines. 952 51

CC chemokine receptor 5 (CCR5) functions physiologically as a receptor for the leukocyte chemoattractants macrophage inflammatory protein-1alpha, macrophage inflammatory protein-1beta, and RANTES, and functions pathologically as a key cell entry coreceptor for HIV-1. The factors that regulate CCR5 expression may be useful therapeutic targets for HIV-1 infection. To identify nuclear regulatory factors, we have located and functionally characterized the CCR5 gene promoter. The gene consists of two exons separated by a 1.9-kb intron. Exon 1 contains 43 bp of the 5'-untranslated region; exon 2 contains 11 bp of the 5'-untranslated region and the complete open reading frame. Primer extension analysis identified two adjacent transcriptional start points (tsp) that map to the first 2 bp found in the longest known CCR5 cDNA sequence. A TATA box is present 31 bp upstream from the first tsp. CCR5 mRNA was detected constitutively in both primary human myeloid and lymphoid cells by Northern blot hybridization. Consistent with this, transcription of a chloramphenicol acetyltransferase reporter gene was constitutively activated in both transiently transfected myeloid and lymphoid cell lines by the 80-bp gene fragment located immediately upstream of the tsp. Deletion analysis located a strong silencer element between nucleotides -244 and -80, and a strong enhancer element between -486 and -244. These results suggest that the gene region between -486 and -1 may regulate the expression of CCR5 in monocyte/macrophages and T lymphocytes.
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PMID:Gene organization and promoter function for CC chemokine receptor 5 (CCR5). 955 38


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