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

To delineate the cis-acting element through which EBNA-2 transactivates latent membrane protein 1 (LMP1), we assayed the effect of EBNA-2 on the activity of LMP1 promoter upstream deletion mutants in the context of the LMP1 or heterologous promoters controlling chloramphenicol acetyltransferase (CAT) reporter gene expression in Epstein-Barr virus-negative Burkitt lymphoma cells. Assays of progressive 5' deletions of the LMP1 promoter revealed low constitutive and at least eightfold EBNA-2-stimulated activity from -512 to +40 (-512/+40), -334/+40, and -234/+40 LMP1CAT plasmids. More extensive 5'-deleted -205/+40, -155/+40, and -147/+40 LMP1CAT plasmids also had low constitutive activity but were not EBNA-2 responsive. The most 5'-deleted -55/+40 LMP1CAT plasmid had moderate constitutive activity and was not EBNA-2 inducible. Either orientation of the -334/+40 LMP1 sequence conferred EBNA-2 responsiveness when positioned upstream of an enhancerless simian virus 40 or herpes simplex virus thymidine kinase (TK) promoter. EBNA-2 and the cis-acting LMP1 DNA were both required to increase TK promoter-initiated mRNA, indicating that the EBNA-2 effect is at the transcriptional level. Further deletion analysis of the EBNA-2-responsive cis-acting element defined a -234/-92 LMP1 DNA fragment which conveyed EBNA-2 responsiveness to the herpes simplex virus TK promoter. The 5' 30 bp between -234 and -205 were essential for EBNA-2 responsiveness. Thus, these experiments define a 142-bp cis-acting element which is sufficient for conveying EBNA-2 responsiveness and an essential 30-bp component of that element. The role of this element in LMP1 and LMP2B expression and its possible role in LMP2A expression are discussed.
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PMID:Delineation of the cis-acting element mediating EBNA-2 transactivation of latent infection membrane protein expression. 165 73

Of the eight viral antigens known to be expressed during Epstein-Barr virus latency, six are transcribed from a major rightward transcriptional unit, which gives rise to mRNAs containing common 5' exons. Analysis of cDNA clones has identified the use of two different promoters (Wp and Cp), located near the left-hand end of the viral genome, in generating these viral messages. Characterization of the activities of these two viral promoters in a number of Burkitt lymphoma and lymphoblastoid cell lines has revealed exclusive usage of only one of these promoters in all cell lines examined. Transfection of reporter constructs containing Wp and/or Cp linked to the bacterial chloramphenicol acetyltransferase gene into several different Epstein-Barr virus-infected cell lines generally supports a model in which the mutually exclusive use of Cp or Wp is determined by cellular factors and not by viral strain variation.
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PMID:Mutually exclusive use of viral promoters in Epstein-Barr virus latently infected lymphocytes. 254 39

A 95-base-pair immediate upstream sequence of the human class II major histocompatibility complex DQB gene containing the conserved X and Y elements showed enhancer activity in a transient expression assay. An "enhancer test plasmid" harboring the bacterial chloramphenicol acetyltransferase gene under the control of a truncated simian virus 40 enhancerless early promoter was employed. The DQB sequence inserted into this plasmid was active as an enhancer in Raji cells (human Burkitt lymphoma cells) but not active in Jurkat cells (human T-cell leukemia cells) or in HeLa cells (human cervical carcinoma cells). This cell-type specificity suggests that this enhancer activity may be involved in the tissue specificity of the DQB gene that is normally expressed only in mature B cells, macrophages, and thymic epithelial cells. Deletion analysis showed that both X and Y box sequences are essential for the full activity of the enhancer sequence and that these two sequences may function in a cooperative manner as cis-acting elements. Further deletions were used to define the 5' border of the X element. These results suggest that previously characterized protein factors that bind to X and Y include transcription factors involved in the cell-type specificity of this enhancer activity.
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PMID:B-cell-specific enhancer activity of conserved upstream elements of the class II major histocompatibility complex DQB gene. 313 78

We have used a competition assay to identify the targets of trans-acting elements that modulate the expression of the human c-myc gene (designated MYC in human gene nomenclature). For this purpose, a c-myc hybrid indicator gene was formed by joining the c-myc promoter region, first noncoding exon, and intron to the bacterial gene for chloramphenicol acetyltransferase (CAT). The test assay consisted of cotransfecting the indicator gene with competing fragments of DNA derived from suspected control regions of the c-myc gene. Such experiments test the hypothesis that control regions are often targets for the binding of trans-acting regulatory factors that can be diverted to competing fragments of DNA. A negatively acting element will be diverted from the indicator gene, allowing the gene's enhanced expression, whereas a positively acting element will behave oppositely. Control indicator genes driven by non-myc promoters assess the specificity of the effect. Using this approach, we find three c-myc regions that are capable of enhancing the expression of the indicator gene in competition assays (i.e., putative sites of negative modulation). In addition, we find sequences near the c-myc promoters that suppress expression in competition assays (i.e., putative binding sites of positively acting factors). These results, with appropriate controls, suggest the existence of target sites near the c-myc gene that specifically modulate its expression both positively and negatively. Their locations fit well with regions damaged or lost in many Burkitt lymphoma and murine plasmacytoma translocations.
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PMID:Trans-acting elements modulate expression of the human c-myc gene in Burkitt lymphoma cells. 346 6

Disruption of Epstein-Barr virus (EBV) latency is mediated by ZEBRA, the protein product of the immediate-early EBV gene, BZLF1. In vitro, phorbol 12-myristate 13-acetate (PMA), a potent activator of protein kinase C (PKC), induces reactivation of EBV. However, the physiological stimuli responsible for the disruption of viral latency are not well characterized. Transforming growth factor beta 1 (TGF-beta1) has also been shown to trigger the reactivation of EBV in Burkitt lymphoma cell lines; however, the effect of TGF-beta1 on ZEBRA expression has not been reported. To further understand this phenomenon, we have investigated the effect of TGF-beta1 on ZEBRA expression. Our results indicate that the treatment of different EBV-positive Burkitt's lymphoma cell lines with TGF-beta1 induces a time-dependent activation of BZLF1 transcription with a corresponding increase in the production of the protein ZEBRA. TGF-beta1 has been shown to exert its effects through a wide range of intracellular routes; in the present study, we have explored these pathways. Transient expression of Smad proteins on their own had no effect on ZEBRA expression. A specific inhibitor of p38 mitogen-activated protein kinase (MAPK), SB203580, did not affect TGF-beta1-induced ZEBRA expression, whereas treatment with the MAPK/ERK kinase inhibitors, PD98059 and U0126, dramatically decreased this induction. This suggests that TGF-beta1 effect on BZLF1 expression requires the MAPK pathway. However, in Raji and B95-8 cells additional routes can be used, as (i) the inhibition of ZEBRA induction by PD98059 or U0126 was incomplete, whereas these inhibitors completely abolished PMA-induced ZEBRA expression, (ii) TGF-beta1 induction of ZEBRA expression occurs in PKC-depleted cells, (iii) in Raji and in B95-8 cells, the effect of TGF-beta1 and PMA are additive. Transient transfection of the EBV-negative B-cell line DG75 with a BZLF1 promoter-fusion construct (Zp-CAT) showed that under conditions where the BZLF1 promoter is activated by PMA treatment, TGF-beta1 had no significant effect on the expression of the chloramphenicol acetyltransferase gene. Furthermore, TGF-beta1 induction of BZLF1 transcripts is dependent on de novo protein synthesis, which suggests that TGF-beta1 induces BZLF1 expression by an indirect mechanism.
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PMID:Transforming growth factor beta 1 stimulates expression of the Epstein-Barr virus BZLF1 immediate-early gene product ZEBRA by an indirect mechanism which requires the MAPK kinase pathway. 1084 60