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)

We developed a novel promoter system, designated SR alpha, which is composed of the simian virus 40 (SV40) early promoter and the R segment and part of the U5 sequence (R-U5') of the long terminal repeat of human T-cell leukemia virus type 1. The R-U5' sequence stimulated chloramphenicol acetyltransferase (CAT) gene expression only when placed immediately downstream of the SV40 early promoter in the sense orientation. The SR alpha expression system was 1 or 2 orders of magnitude more active than the SV40 early promoter in a wide variety of cell types, including fibroblasts and lymphoid cells, and was capable of promoting a high level of expression of various lymphokine cDNAs. These features of the SR alpha promoter were incorporated into the pcD-cDNA expression cloning vector originally developed by Okayama and Berg.
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PMID:SR alpha promoter: an efficient and versatile mammalian cDNA expression system composed of the simian virus 40 early promoter and the R-U5 segment of human T-cell leukemia virus type 1 long terminal repeat. 282 8

The immunoglobulin heavy-chain enhancer is a cis-acting element which activates transcription of nearby genes only in cells of the lymphoid lineage. To identify the minimal sequences necessary to impart cell type transcriptional specificity, we tested the activity of several deletions and internal mutations in the mu enhancer. Experiments involving measurement of both chloramphenicol acetyltransferase activity and RNA levels indicated the presence of a dominant repressor element within the mu enhancer. This repressive activity was detected in fibroblasts but not in myeloma cells. Removal or disruption of this repressor element revealed the presence of elements within the mu enhancer that activate transcription in fibroblasts. Thus, enhancer tissue specificity is in part due to the composite of both constitutive activation and cell-type-specific repressive activity. The possible biological roles of this phenomenon are discussed.
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PMID:Localization of a repressive sequence contributing to B-cell specificity in the immunoglobulin heavy-chain enhancer. 283 47

Six cloned 5' long terminal repeat (LTR) and adjoining cellular DNA regions of partially deleted feline endogenous RD-114 proviral loci were linked to the chloramphenicol acetyltransferase (CAT) gene and assayed for their ability to promote transient CAT expression. One endogenous LTR (clone CRL-3) and the LTR from an infectious RD-114 provirus, EX-LTR, were capable of actively expressing the CAT gene. DNA sequence comparison of these LTRs with an inactive endogenous LTR (CR-1) revealed extensive homology in all regions except in the 5' half of U3. The homologous portion contained transcriptional regulatory sequences including CAT, TATA, polyadenylation signal boxes and an octamer enhancer, which is rarely seen in retroviruses. Variations in the 5' half of U3 were primarily due to insertions and deletions. A major difference was in number of copies and integrity of tandemly repeated sequences. EX-LTR contained two pairs of tandem direct repeats, while the two endogenous LTRs contained different deletions of repeated sequences. DNA sequence data also revealed that the primer binding site for RD-114 loci was complementary to a glycine tRNA isotype, the use of which is distinct from any other known retrovirus. An analysis of the steady state RNA levels in T-lymphoid cell lines showed that at least three different incomplete proviral transcripts and their spliced products made up the majority of expressed RD-114 mRNA, and further demonstrated that partially deleted proviral loci have the potential to be transcriptionally vigorous in certain feline cell types.
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PMID:The long terminal repeat of feline endogenous RD-114 retroviral DNAs: analysis of transcription regulatory activity and nucleotide sequence. 283 49

The promoter and 5' flanking region of the mouse Thy-1.2 glycoprotein gene were characterized by DNA sequencing, primer extension analysis, and deletion analysis. Transcriptional initiation sites were identified which corresponded to two separate exons upstream of the portion of the gene encoding the Thy-1.2 glycoprotein. We demonstrated that the mouse Thy-1.2 gene was transcribed from two atypical promoters separated by 260 base pairs in the genomic sequence. These promoters contained neither TATAAG nor GGPyCCAATCT homologous sequences but defined a conserved nonamer CTCCCTGCT at -48 from each initiation site. Two Thy-1.2 mRNA species of 1,835 and 1,939 nucleotides, differing in the 5' untranslated region of the mRNA, were thus transcribed from the single Thy-1.2 gene by mRNA splicing to the same downstream exon. Recombinant genomes in which the bacterial chloramphenicol acetyltransferase gene was expressed from either of the two Thy-1.2 promoters demonstrated that each promoter functioned independently and did not direct cell-specific expression in lymphoid cells. The 5' flanking region of the Thy-1.2 gene upstream of -68 could be eliminated without altering cell-type-specific expression. This suggests that regulatory elements responsible for tissue and developmental stage-specific expression of the Thy-1.2 gene are not present in the 5' flanking DNA but may reside downstream of the promoters.
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PMID:Characterization of two atypical promoters and alternate mRNA processing in the mouse Thy-1.2 glycoprotein gene. 287 65

The acquired immune deficiency syndrome (AIDS) retrovirus, HTLV-III/LAV, encodes a transacting factor which directly or indirectly stimulates the expression of genes linked to its LTR. To further dissect this phenomenon, we have cotransfected a biologically active molecular clone of HTLV-III and a recombinant plasmid containing an indicator gene, the bacterial gene for chloramphenicol acetyltransferase (CAT), under the control of the HTLV-III LTR. Amplified CAT activity was detected in both lymphoid cells and fibroblasts from a number of species in the presence of the proviral DNA. Deletion experiments confirm the previous assignment of the gene required for transactivation to a region immediately 5' to the envelope gene, and further narrow down the critical functional domain to a coding sequence of 58 codons.
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PMID:Transactivation induced by human T-lymphotropic virus type III (HTLV III) maps to a viral sequence encoding 58 amino acids and lacks tissue specificity. 300 31

The ability of the sequences present in the long terminal repeats (LTRs) of human T-cell leukemia viruses type I and II (HTLV-I and HTLV-II) and of bovine leukemia virus to function as enhancer elements was investigated. Recombinant plasmids that contained the HTLV-I, HTLV-II, and bovine leukemia virus LTRs at a distance from a simian virus 40 promoter element located 5' to the bacterial gene encoding chloramphenicol acetyltransferase (EC 2.3.1.28) were constructed. We report that all three LTR sequences contain enhancer elements capable of increasing the level of gene expression directed from a distal heterologous promoter. The enhancer present in the HTLV-I LTR was active in uninfected cells of lymphoid and nonlymphoid origin. In contrast, the enhancer activity of the HTLV-II and bovine leukemia virus LTR sequences was evident only in virus-infected cells. This activity is likely due to virus-associated trans-acting transcriptional factors previously shown to be present in HTLV- and bovine leukemia virus-infected cells. The implication of these observations for virus replication and transforming activity are discussed.
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PMID:Activation of enhancer sequences in type II human T-cell leukemia virus and bovine leukemia virus long terminal repeats by virus-associated trans-acting regulatory factors. 300 24

We isolated the full length provirus of human T cell leukaemia virus type I (HTLV-I) from MT-2, a lymphoid cell line producing HTLV-I. In three non-lymphoid cell lines (COS7, human osteosarcoma HOS cells, and HeLa) this provirus expressed a trans-acting activity after co-transfection with a recombinant plasmid carrying a bacterial chloramphenicol acetyltransferase gene under the control of a long terminal repeat of HTLV-I provirus. The trans-acting protein p40 was detected by immunoprecipitation in transfected HOS cells. Structural proteins of HTLV-I, the gag and env products, were also formed and processed in the same manner as observed in MT-2 cells. In transfected HeLa cells, the p40 protein was mainly localized in the nucleus, while other structural proteins were detected in the cytoplasm and/or the membrane by indirect immunofluorescence. Syncytium formation was observed in HeLa cells after transfection. These results demonstrated that non-lymphoid cells could produce the major proteins of HTLV-I after DNA transfection of the cloned provirus.
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PMID:Expression of a provirus of human T cell leukaemia virus type I by DNA transfection. 302 87

The immunoglobulin kappa light chain gene contains a lymphoid-specific enhancer that includes several short protein-binding sequences. The sequence that binds the nuclear factor NF-kappa B was tested for its ability to act independently as an enhancer element by inserting it into test plasmids containing the chloramphenicol acetyltransferase gene. When analyzed for activity by transient transfection into lymphoid and nonlymphoid cells, a single copy of the NF-kappa B binding site could act as a tissue-specific upstream activating element. Two copies (dimer) showed 10-fold higher activity than did one copy and could act as an enhancer element 2.5 kilobases downstream of the transcriptional start site. The enhancer activity of this sequence was correlated with the presence of the cognate binding protein, NF-kappa B. This sequence acted as an inducible enhancer under conditions that induce NF-kappa B binding activity. Thus, the NF-kappa B binding site acts by itself as a tissue-specific and inducible enhancer element, and two copies show cooperative interaction.
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PMID:Oligonucleotide that binds nuclear factor NF-kappa B acts as a lymphoid-specific and inducible enhancer element. 312 49

The p53 is a nuclear protein that is associated with normal cellular proliferation and can cooperate with Ha-ras in causing cellular transformation in vitro. Lineage association is known to exist between p53 expression and normal lymphopoiesis, but not myelopoiesis. We studied the expression of p53 using chronic myelogenous leukemia (CML) cell lines, somatic hybrids of these cells, and leukemic cells from CML patients. Lymphoid CML lines expressed both p53 mRNA and protein. We also analyzed p53 synthesis by two B-lymphoid lines from the same CML patient; cells of one line were derived from the neoplastic clone, cells of the other were derived from the normal clone. Both synthesized equal amounts of a phosphorylated p53 protein. None of the myeloid CML lines expressed detectable p53 protein and two of four expressed negligible p53 mRNA. Two other myeloid CML lines and myeloid cells from three of four patients expressed p53 mRNA. These findings suggest that expression of the gene is not regulated normally in CML. Several approaches were pursued to explore the differential expression of p53. Southern blot analyses showed no gross alterations in the p53 gene from cells of either the expressing or the nonexpressing lines. No difference in the pattern of demethylated CpG sites was noted in the region of the p53 gene in cells from K562 (myeloid p53 nonexpressor) and in BV173 (lymphoid p53 expressor). The sites of demethylation clustered in and around the p53 promoter in both cell lines. Somatic hybrids formed between a p53 mRNA nonexpressor myeloid line (K562) and the parental p53 expressor lymphoid lines (Daudi, PUT) produced p53 mRNA and protein, suggesting that p53 is a dominantly expressed protein and that lack of expression in myeloid cells is not mediated by a trans-acting negative regulatory protein. DNA transfection experiments performed using the indicator gene chloramphenicol acetyltransferase attached to promoter sequences of p53 showed that these constructs were equally activated in BV173 (p53 expressor) and K562 (p53 mRNA nonexpressor). The mechanism of p53 regulation in CML remains unclear.
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PMID:p53 in chronic myelogenous leukemia. Study of mechanisms of differential expression. 328 Jul 26

The technique of DNA transfer by electroporation was investigated in an effort to evaluate its utility for the identification of developmentally controlled regulatory sequences. Transient and stable gene expression was detected in a variety of lymphoid cell lines subjected to electroporation. No correlation existed between the levels of chloramphenicol acetyltransferase (acetyl-CoA; chloramphenicol 3-O-acetyltransferase, EC 2.3.1.28) expression and stable transfection frequency. In all lymphoid cell lines tested, the simian virus 40 early region was a better promoter than was the Rous sarcoma virus long terminal repeat.
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PMID:Electric field-mediated DNA transfer: transient and stable gene expression in human and mouse lymphoid cells. 346 22


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