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)

Transcription of the complete mouse mammary tumor virus (MMTV) proviral genome in mouse cells is controlled by a strong promoter in its long terminal repeat. In the mouse T lymphoma EL4, there is a second, activation-dependent transcriptional initiation site within the envelope (env) gene, from which a short mRNA is generated, encoding the open reading frame of the long terminal repeat. We now report the isolation of a segment of the MMTV env gene (called META, for MMTV env transcriptional activator) which has the expected transcription-activating properties seen in EL4.E1 cells. Namely, it induces activation-dependent, T-lymphocyte-specific transcription of a chloramphenicol acetyltransferase reporter gene. It is active in mouse or human T-helper lymphocyte lines when they are stimulated to transcribe lymphokine genes but is inactive in unstimulated T-helper cells, fibroblasts, a cytotoxic T-lymphocyte line, and a mastocytoma cell line. Its activity is inhibited by cyclosporin A, a specific inhibitor of lymphokine transcription. Several forms of the META have been isolated from EL4.E1 cells, a mouse T-helper cell hybridoma, and from BALB/c spleen cells. Linked to the heterologous thymidine kinase promoter, a 400-bp portion of it is an inducible, orientation-independent, and cyclosporin A-sensitive transcriptional activator in T-helper cells.
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PMID:An activation-dependent, T-lymphocyte-specific transcriptional activator in the mouse mammary tumor virus env gene. 132 Jan 98

The c-myb protooncogene, which is preferentially expressed in hematopoietic cells at the G1/S boundary of the cell cycle, encodes a transcriptional activator that functions via DNA binding. The regulatory mechanisms governing this specific pattern of expression are not fully understood, although human c-myb expression appears to be positively autoregulated via myb-binding sites in the 5'-flanking region of the c-myb gene (Nicolaides, N. C., Gualdi, R., Casadevall, C., Manzella, L., and Calabretta, B. (1991) Mol. Cell. Biol. 11, 6166-6176). To determine the contribution of other transcription regulators such as JUN family members in the control of c-myb expression, transient expression assays were carried out which revealed a 6- to a 15-fold enhancement by c-Jun and JunD, but not JunB, in chloramphenicol acetyltransferase reporter gene expression driven by different segments of the human c-myb 5'-flanking region. An Ap1-like element located at nucleotide -149 from the c-myb initiation site appears to be required for this transactivation upon binding to a nuclear protein complex containing c-Jun and JunD, since site-directed mutations of this Ap1-like element abolished c-Jun and JunD binding and transactivation. Exposure of phytohemagglutinin-stimulated peripheral blood mononuclear cells to c-jun and junD antisense oligodeoxynucleotides resulted in a 46 and 43% inhibition of T-lymphocyte proliferation that was accompanied by a decrease in c-myb mRNA levels as compared with sense-treated cultures. Because T-lymphocytes induced to proliferate express c-jun and junD before c-myb, these data suggest a mechanism whereby c-Jun and JunD contribute to the transcriptional activation of c-myb that, in turn, is maintained at the G1/S transition and during S phase by positive autoregulation.
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PMID:The Jun family members, c-Jun and JunD, transactivate the human c-myb promoter via an Ap1-like element. 152 86

We have replaced the polyomavirus (Py) enhancer, which is an essential component of the Py origin of DNA replication (ori), with five repeats of a 17-bp oligonucleotide including the yeast GAL4 upstream activating sequence (5xGAL4 sites). Plasmids containing this modified Py ori, designated test plasmids, and plasmids encoding either the GAL4 transcriptional activator protein or various derivatives of this protein were cotransfected into mouse cells which constitutively synthesize a temperature-sensitive Py large tumor antigen (T-Ag). Replication of the test plasmids was monitored by Southern blot determinations of the amounts of plasmid DNA that became resistant to cleavage by the enzyme DpnI. These studies showed that in the presence of a functional T-Ag, the GAL4 protein, and hybrid proteins including the GAL4 DNA-binding domain and the activating domain of the adenovirus E1a or herpesvirus VP16 protein transactivated the modified Py ori. A truncated protein including just the GAL4 DNA-binding domain was inactive in these assays. The authentic GAL4 protein was found to be a more efficient replication transactivator than the hybrid proteins. In contrast, chloramphenicol acetyltransferase assays showed that the hybrid proteins were more efficient transcriptional activators than the GAL4 protein. The extent of the GAL4-dependent replication of a plasmid in which the Py early promoter was deleted was 55% lower than that of a plasmid including the promoter. However, the extents of replication of plasmids including two tandem repeats of the remaining Py origin core and 5xGAL4 sites or two origin cores flanking a single cluster of 5xGAL4 sites were 4.8- and 1.6-fold higher than that of the plasmid including a single copy of each element. The replication of a plasmid including two clusters of 5xGAL4 sites flanking a single origin core was below the limit of detection of our assays. These results indicate that the GAL4 and hybrid transactivators do not activate the Py ori by virtue of their interactions with transcription factors that bind promoter elements. Rather, it appears that these activator proteins may interact with the replication initiation complexes, thereby facilitating or inhibiting the initiation of replication.
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PMID:The yeast GAL4 protein transactivates the polyomavirus origin of DNA replication in mouse cells. 164 81

The Epstein-Barr virus BZLF1 gene product (ZEBRA) is a transcriptional activator whose expression in latently infected B cells is sufficient to induce the viral lytic cycle. Since there is no transcription of BZLF1 during latency, we carried out experiments to determine whether cis-acting negative elements in the BZLF1 promoter contribute to the lack of expression during this phase of the virus cycle. A series of deletion plasmids encompassing positions -551 to +14 of the BZLF1 promoter region were constructed and tested for the ability to drive chloramphenicol acetyltransferase (CAT) gene expression in the absence of inducing agents such as 12-O-tetradecanoylphorbol-13-acetate (TPA) and anti-immunoglobulin. Expression from the intact 551-bp region was very weak in most of the cell lines tested, but deletion of 165 bp from the 5' end caused a sevenfold increase in expression of CAT. Within these 165 bp, a minimal 48-bp region was sufficient to down regulate the expression of a simian virus 40/CAT fusion plasmid. The 48-bp negative element consists of 7-bp dyad symmetry elements separated by 27 bp. The rightmost half of the dyad symmetry element partially overlaps a region which has a 14-of-15-bp homology to the human cytoskeletal gamma-actin promoter.
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PMID:Negative regulation of the BZLF1 promoter of Epstein-Barr virus. 164 87

The NF-kappa B transcription factor complex is composed of two proteins, designated p50 and p65, both having considerable homology to the product of the rel oncogene. We present evidence that the p65 subunit is a potent transcriptional activator in the apparent absence of the p50 subunit, consistent with in vitro results demonstrating that p65 can interact with DNA on its own. To identify the minimal activation domain, chimeric fusion proteins between the DNA binding domain of the yeast transcriptional activator protein GAL4 and regions of the carboxy terminus of p65 were constructed, and their transcriptional activity was assessed by using a GAL4 upstream activation sequence-driven promoter-chloramphenicol acetyltransferase fusion. This analysis suggests that the boundaries of the activation domain lie between amino acids 415 and 550. Moreover, single amino acid changes within residues 435 to 459 greatly diminished activation. Similar to other activation domains, this region contains a leucine zipper-like motif as well as an overall net negative charge. To identify those residues essential for DNA binding, we made use of a naturally occurring derivative of p65, lacking residues 222 to 231 (hereafter referred to as p65 delta), and produced via an alternative splice site. Gel mobility shift analysis using bacterially expressed p65, p65 delta, and various mutants indicates that residues 222 to 231 are important for binding to kappa B DNA. Coimmunoprecipitation analysis suggests that these residues likely contribute to the multimerization function required for homomeric complex formation or heteromeric complex formation with p50 in that no association of p65 delta with itself or with p50 was evident. However, p65 delta was able to form weak heteromeric complexes with p65 that were greatly reduced in their ability to bind DNA. On the basis of these findings, we suggest that subtle changes within the proposed multimerization domain can elicit different effects with the individual Rel-related proteins and that a potential role of p65 delta may be to negatively regulate NF-kappa B function through formation of nonfunctional heteromeric complexes.
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PMID:Functional characterization of the NF-kappa B p65 transcriptional activator and an alternatively spliced derivative. 173 26

The ets oncogene superfamily consists of a family of sequence-specific DNA-binding proteins that activate transcription. We have previously identified two new members of the ets oncogene superfamily, namely elk-1 and elk-2. In this report we show that the recombinant elk-1 protein expressed in bacteria, like the c-ets-1 proto-oncogene, binds in a sequence-specific manner to Moloney murine sarcoma virus long terminal repeat, E74 target sequences and the PEA3 motif (polyoma enhancer), but does not bind to PU box sequences. Thus analysis of the DNA-binding specificity of ets-related proteins supports the view that different members show similar DNA-binding specificity, which is a general feature of the homeobox proteins. Our data using the chloramphenicol acetyltransferase gene linked to a thymidine kinase promoter containing multimers of the elk-1 target sequence indicates that elk-1 functions as a transcriptional activator. Interestingly, although elk-1 is the most divergent of all the members of the ets gene family, it shows very close similarities with c-ets-1 in some of its sequence-specific DNA-binding specificities. Here, we propose a new function for the elk-1 gene to act as a transcriptional activator of retroviruses and DNA tumor viruses.
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PMID:A divergent ets-related protein, elk-1, recognizes similar c-ets-1 proto-oncogene target sequences and acts as a transcriptional activator. 174 Nov 66

We have recently shown that the human apoA-II promoter contains a set of 11 distal regulatory elements between nucleotides -903 and -255 and three proximal regulatory elements between nucleotides -126 and -33 that are essential for hepatic and intestinal transcription of the apoA-II gene (Chambaz, J., Cardot, P., Pastier, D., Zannis, V. I., and Cladaras, C. (1991) J. Biol. Chem. 266, 11676-11685). Deletion or nucleotide substitution analysis has shown that alterations in elements L (nucleotides -803 to -773) and K (nucleotides -760 to -743) reduced hepatic transcription to 25 and 20% and intestinal transcription to 8 and 4% of control, respectively, as measured by chloramphenicol acetyltransferase assays, indicating that these elements play an important regulatory role. Nucleotide substitutions in element AB (nucleotides -65 to -33) reduced hepatic and intestinal transcription to 60 and 36% of control, respectively. The factors that recognize regulatory regions L, K, and AB were analyzed by DNA binding gel electrophoretic and competition assays. This analysis has shown that elements AB, K, and L bind with different affinities to a newly characterized heat-stable factor, CIIIB1, which is a transcriptional activator of the human apoC-III gene (Ogami, K., Kardassis, D., Cladaras, C., and Zannis, V. I. (1991) J. Biol. Chem. 266, 9640-9646). In addition, elements AB and K bind a heat-labile activity, designated AIIAB1, and element L binds to several CCAAT box binding activities. Mutations in domain L that prevented the binding of CCAAT box binding activities reduced both hepatic and intestinal transcription to 30% of control, indicating the importance of these factors in transcription. Simultaneous nucleotide substitutions that prevented the binding of CIIIB1 activity in elements AB, K, and L reduced hepatic and intestinal transcription to 7 and 6% of control, respectively, suggesting that the synergistic interaction of CIIIB1 (bound to the proximal and distal regulatory elements) with CCAAT box proteins (bound to element L) can modulate the level of transcription of the human apoA-II gene.
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PMID:Regulation of the human ApoA-II gene by the synergistic action of factors binding to the proximal and distal regulatory elements. 176 46

We present evidence that CRE-BP1 binding to the cyclic AMP (cAMP) response element (CRE) is a transcriptional activator. Transcriptional activation was assayed by cotransfection into CV-1 cells of a CRE-BP1 expression plasmid together with a reporter plasmid in which the thymidine kinase promoter and four tandem repeats of CRE were linked to the chloramphenicol acetyltransferase (CAT) gene. Cotransfection with the CRE-BP1 expression plasmid caused an 8-fold stimulation of CAT activity, while cotransfection with the plasmids to express CRE-BP1 and c-Jun induced a 32-fold stimulation of CAT activity, suggesting that a heterodimer of CRE-BP1 with c-Jun is a stronger trans-activator than a homodimer of CRE-BP1. By using a series of deletion and point mutants of CRE-BP1 in this cotransfection assay, two functional domains of CRE-BP1 were identified: the putative metal finger structure in the amino-terminal region and the leucine zipper motif linked to a cluster of basic amino acids in the carboxyl-terminal region. The former was a transcriptional activation domain in the absence of c-Jun. The latter was a DNA-binding domain, and was essential in both the presence and absence of c-Jun.
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PMID:Identification of the functional domains of the transcriptional regulator CRE-BP1. 183 93

The nucleotide sequence of the pol-env intergenic region of two isolates of caprine arthritis-encephalitis virus (CAEV) was determined. Two open reading frames (orfs) were identified, designated Q and S by homology with visna virus. CAEV orf S is a single exon encoding a deduced 87-amino acid gene product sharing 36 amino acid identities with the visna trans-acting transcriptional activator (Tat). Ten of these identities comprise a conserved CGCRLCNPGW sequence similar to a cysteine-rich domain essential for trans-activation by human immunodeficiency virus Tat. To determine if transcription promoted by the CAEV long terminal repeat (LTR) could be stimulated in CAEV-infected goat synovial membrane cells, a plasmid (pCAE-CAT) expressing bacterial chloramphenicol acetyltransferase (CAT) under control of the CAEV LTR was transfected into uninfected and infected cells. Sixfold enhancement of CAT activity was observed in infected cells using 100 ng of transfected plasmid. To determine if the pol-env region encodes a gene product which trans-activates the CAEV LTR, goat synovial membrane cells were cotransfected with pCAE-CAT and pRSV-1.9, a plasmid expressing the pol-env region under control of the Rous sarcoma virus LTR. Results indicated that the CAEV genome encodes a tat gene product attributable to orf S.
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PMID:Genetic structure of the pol-env region of the caprine arthritis-encephalitis lentivirus genome. 184 32

The hns (27 min) gene encoding the 15.4-kDa nucleoid protein H-NS was shown to belong to the cold shock regulon of Escherichia coli, its expression being enhanced 3- to 4-fold during the growth lag that follows a shift from 37 degrees C to 10 degrees C. A 110-base-pair (bp) DNA fragment containing the promoter of hns fused to a promoterless cat gene (hns-cat fusion) conferred a similar cold shock response to the expression of chloramphenicol acetyltransferase (CAT) activity in vivo and in coupled transcription-translation systems prepared with extracts of cold-shocked cells. Extracts of the same cells produce a specific gel shift of the 110-bp DNA fragment and this fragment, immobilized on a solid support, specifically retains a single 7-kDa protein present only in cold-shocked cells that was found to be identical to F10.6 (CS7.4), the product of cspA. This purified protein, which is homologous to human DNA-binding protein YB-1, recognizes some feature of the 110-bp promoter region of hns and acts as a cold shock transcriptional activator of this gene since it stimulates the expression of CAT activity and of cat transcription in in vitro systems programmed with plasmid DNA carrying the hns-cat fusion.
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PMID:Identification of a cold shock transcriptional enhancer of the Escherichia coli gene encoding nucleoid protein H-NS. 196 61


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