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)

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.
 ...
PMID:Mutually exclusive use of viral promoters in Epstein-Barr virus latently infected lymphocytes. 254 39

We studied the regulatory region of the open reading frame BHRF1 of Epstein-Barr virus (EBV) DNA that was responsive to two trans-activators (Z and R) encoded by the BZLF1 and BRLF1, respectively. The 200-bp sequence, nucleotide numbers 53,617 to 53,817 on the EBV map, was sufficient for conferring responsiveness to Z and R. This 200-bp sequence also enhanced expression of the chloramphenicol acetyltransferase (CAT) gene from the simian virus 40 promoter in response to both Z and R, even when inserted downstream of the cat gene. The results indicate that the Z and R response sequence upstream of the BHRF1 has the properties of an enhancer.
 ...
PMID:Identification of an enhancer-type sequence that is responsive to Z and R trans-activators of Epstein-Barr virus. 255 65

The coding sequence for the hepatitis B virus surface antigen (HBsAg) was used as a new reporter gene for studies on eukaryotic promoter activity and upstream regulatory sequences. The data observed in transfection assays were comparable to results obtained with conventional chloramphenicol acetyltransferase (CAT) assays, as was demonstrated using various transcriptional regulation sequences. The expression of HBsAg as a reporter protein offered some advantages: (i) In transient expression assays, a time course of promoter activity depending on variable culture conditions could be monitored over a period of time, since the HBsAg was secreted into the culture supernatant. (ii) Evaluation of HBsAg from supernatant aliquots and quantification of the corresponding promoter activities could be performed easily, using the very sensitive and readily available diagnostic HBsAg kits. (iii) In contrast to the conventional CAT assay, the cells remained available for further tests, e.g., Western blot, immunofluorescence or transcript analysis. Characteristics of several Epstein-Barr virus (EBV) promoters, depending on the virus state of EBV-positive B-cells (latency, chemical induction, lytic superinfection, trans-activation), were assayed using the HBsAg reporter system.
 ...
PMID:Hepatitis B virus surface antigen as a reporter of promoter activity. 255 36

We have demonstrated that gene expression from the promoter of the Epstein-Barr virus (EBV) MS gene with its upstream sequence is inducible by 12-O-tetradecanoylphorbol-13-acetate (TPA). By transfecting mammalian cells with plasmids in which the MS promoter and its upstream sequence are linked to the bacterial chloramphenicol acetyltransferase gene, we have shown that treatment of the cells with TPA stimulates the expression of chloramphenicol acetyltransferase activity in both EBV-negative and -positive cell lines. This TPA response requires the cis-acting sequence between nucleotides 84440 and 85046 of the EBV genome, located either upstream or downstream of the MS promoter. The TPA induction is at the transcriptional level. When this sequence is linked to the promoter of the human herpesvirus 1 thymidine kinase gene, it can also enhance the expression of, and confer TPA responsiveness on, the thymidine kinase promoter. By constructing and transfecting mutants with 5' and 3' deletions, we have identified two TPA-responsive elements, one located between -726 and -690 and the other located between -603 and -546 relative to the transcription start site. These two sequences do not contain any homology to the previously defined elements for TPA response and may play an important role in EBV induction by TPA.
 ...
PMID:Novel 12-O-tetradecanoylphorbol-13-acetate-responsive elements in the upstream sequence of the MS gene promoter of Epstein-Barr virus. 255 42

From the cloning and characterization of cDNAs, we found that the Epstein-Barr virus (EBV) open reading frame (ORF) BMLF1-BSLF2 coding for the early protein EB2 is present in several mRNAs generated by alternative splicing and expressed in the leftward direction from two promoters PM and PM1. The PM promoter controls the expression of two abundant mRNA species of 1.9 and 2 kilobases (kb), whereas the PM1 promoter controls the expression of at least three mRNAs 3.6, 4.0, and 4.4 kb long. The PM promoter probably overlaps with the PS promoter which controls the transcription of a 3.6-kb mRNA expressed in the rightward direction and containing the ORF BSRF1. Although it increases the amount of chloramphenicol acetyltransferase enzyme expressed from the chimeric pMCAT gene, EB2 is not a promiscuous trans-activator of gene expression and does not positively regulate its own expression from promoter PM. The EB2 activation is not promoter dependent but could possibly act by stabilizing mRNAs and increasing their translation. The PM promoter is, however, activated by the two EBV transcription trans-acting factors, EB1 and R, encoded by the EBV ORFs BZLF1 and BRLF1, respectively. EB1 activates the PM promoter from a consensus AP-1 binding site, and R activates the PM promoter from an enhancer.
 ...
PMID:The Epstein-Barr virus (EBV) early protein EB2 is a posttranscriptional activator expressed under the control of EBV transcription factors EB1 and R. 255 54

The construction of a mammalian cell expression vector using human cytomegalovirus immediate early gene enhancer to initiate transcription of inserted coding sequences is described. The vector also carries Epstein-Barr virus EBNA-1 nuclear antigen gene, ori-P sequences and hygromycin B resistance gene hph from E. coli. The expression capacity of this construct was tested by inserting the chloramphenicol acetyltransferase (CAT) gene into the vector. The EBV-CAT construct was transfected into various cell lines and high levels of CAT activity were obtained in human and monkey cells. In these cells, the vector DNA also replicates as an extrachromosomal element having 1 to 20 copies per cell. In most cases, the vector copy number and the expression level of inserted gene was in positive correlation in different cell clones.
 ...
PMID:An EBV-based mammalian cell expression vector for efficient expression of cloned coding sequences. 282 66

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

Several Epstein-Barr virus (EBV) early promoters respond to a new EBV transactivator encoded by BRLF1, designated R. Transactivation was measured in chloramphenicol acetyltransferase assays on Raji, BHK, and Vero cells that were cotransfected with the transactivator and target promoters linked to the cat gene. The divergent promoter of BamHI-H was particularly responsive to R transactivation. This large promoter region consists of a leftward TATA box for the NotI repeat gene (BHLF1) and a probable rightward TATA box for the EA-R gene (BHRF1) separated by 940 base pairs of unusual sequence complexity. Sequences within this divergent promoter region appear to confer inducibility by EBV transactivators R and Z (BZLF1). The Z transactivator stimulated expression in both the leftward and rightward directions, and R stimulated expression primarily in the rightward direction, but the MS transactivator (BMLF1) had no activity in either direction. The adenovirus E3 promoter also responded to the R transactivator, but several other herpesvirus and human promoters were nonresponsive. When the divergent promoter was linked to the EA-R gene as it is in the EBV genome, the R and Z transactivators also induced the expression of EA-R in cotransfected cells. This cytoplasmic early antigen is encoded by BHRF1 and may be anchored in intracellular membranes by a carboxy-terminal transmembrane region.
 ...
PMID:A new Epstein-Barr virus transactivator, R, induces expression of a cytoplasmic early antigen. 283 11

To gain insight into how transcription of the human p53 oncogene is controlled, we characterized the regulatory regions of the gene. A 3.8-kilobase-pair (kbp) EcoRI restriction fragment encompassing the 5' end of the human p53 gene, as well as subfragments generated by restriction digests, was cloned upstream of the Escherichia coli chloramphenicol acetyltransferase (CAT) gene and CAT activity was assayed in extracts of transfected cells. Two types of CAT vectors were used: Epstein-Barr virus oriP-derived constructs that were stably introduced into the human cell lines K562, Raji, and HL-60, and pSV0-CAT-derived constructs that were transiently introduced into the monkey cell line COS. By this approach we have identified two promoters for the human p53 gene. One promoter, p53P1, is located 100-250 bp upstream of the 218-bp noncoding first exon; a second, stronger promoter, p53P2, maps within the first intron. CAT activity and expression of CAT RNA indicate that p53P2 functions up to 50-fold more efficiently than p53P1. We conclude that the expression of the human p53 gene may be controlled by two promoters and that differential regulation of these promoters may play an important role in the altered expression of the gene in both normal and transformed cells.
 ...
PMID:Human p53 oncogene contains one promoter upstream of exon 1 and a second, stronger promoter within intron 1. 283 31

We have characterized the properties of an Epstein-Barr virus vector (EBV-CMV) and compared its expression potential with a respective integrating vector (CMV). These vectors were used to express chloramphenicol acetyltransferase (CAT) gene in human HeLa, 293, monkey CV-1, dog MDCK, and hamster R 1610 cells. The EBV-CMV-cat DNA replicates extrachromosomally in HeLa, 293 and CV-1 cells, where also high expression of CAT gene was observed. The EBV-CMV vector integrated in MDCK and R 1610 cells and the CMV vector integrated in all cells tested. Integration yielded mostly clones with low CAT expression. In all cell lines, except HeLa cells, the existence of the extrachromosomal but not the integrated vector DNA is strictly dependent on the Hygromycin B selection pressure. The extrachromosomal state of the EBV vector is a prerequisite for good expression particularly in human and monkey cells.
 ...
PMID:Comparison of mammalian cell expression vectors with and without an EBV-replicon. 285 Jul 83


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