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A Polack

Publications and source records attributed to A Polack.

52 records · Page 3Linked to original sources
PubMed1991

Epstein-Barr virus activators, mutagens and volatile nitrosamines in preserved food samples from high-risk areas for nasopharyngeal carcinoma.

Representative samples of preserved foods collected from high-risk areas for nasopharyngeal carcinoma were assayed for capacity to induce Epstein-Barr virus (EBV) by measuring induction of the DR promoter gene or of genes for early antigens in Raji cells. The two assays gave concordant results, but the DR induction assay detected EBV-inducing substances at lower concentrations and more reproducibly. Three of 17 preserved food items were active in both assays; they were also weakly mutagenic in the SOS chromotest and contained low or moderate levels of volatile N-nitrosamines. After in-vitro nitrosation, the levels of mutagens and nitrosamines increased, whereas EBV-inducing activity was unchanged or decreased. Thus, EBV inducers appear to be a different class of substances from mutagens and volatile N-nitrosamines but could act with them in the etiology of nasopharyngeal carcinoma.

Food Analysis↗
PubMed1991

The intron enhancer of the immunoglobulin kappa gene activates c-myc but does not induce the Burkitt-specific promoter shift.

In Burkitt's lymphoma cells the c-myc gene locus is consistently fused to the constant region of one of the immunoglobulin genes by chromosomal translocation. The translocated c-myc gene is transcriptionally activated and preferentially transcribed from the P1 promoter whenever the exon-intron structure of c-myc remains intact. In order to define elements involved in this promoter shift we have cloned the translocated c-myc allele from Burkitt's lymphoma cell line BL60, which is characterized by several point mutations. The mutated c-myc allele of BL60 was stably introduced into baby hamster kidney and Burkitt's lymphoma cells. S1 nuclease and RNAase protection mapping experiments demonstrated that the mutated c-myc allele was expressed at a low level and with a normal promoter usage (P2 greater than P1) in Burkitt's lymphoma and baby hamster kidney cells. Furthermore, we have studied the expression of a construct consisting of the mutated c-myc allele, part of the bvr1 (Burkitt's variant rearranging region 1) locus, the human immunoglobulin kappa constant region, and the kappa intron enhancer after stable transfection into Burkitt's lymphoma cells. Although c-myc expression was about fivefold increased, the transcripts still initiated predominantly at promoter P2. This indicates that 5 kb of the constant kappa light-chain locus including the kappa intron enhancer is not sufficient to induce the Burkitt's lymphoma-specific promoter shift.

Animals↗
PubMed1990

Expression of P0- and P3-RNA from the normal and translocated c-myc allele in Burkitt's lymphoma cells.

We have studied the allele specific expression of c-myc P0- and P3-RNA in Burkitt's lymphoma (BL) cells. The steady state levels of P0-RNA show considerable variations in BL cells. Expression of P0-RNA was found to be restricted to the translocated allele, but could be induced by TPA from the normal allele. P0-transcription was particularly sensitive to inhibitors of protein synthesis compared to expression of P1-, P2- and P3-RNA. Transcription of P3-RNA is initiated in the first intron of the c-myc gene and has previously been described to be specific for translocated c-myc alleles in BL cells broken within exon 1 or intron 1. Here we show that P3-RNA is also expressed from an unrearranged c-myc gene. In the BL cell line Raji, substantial amounts of c-myc RNA are derived from the P3-promoter of the normal allele. This indicates that repression of the normal allele in BL cells does not include the P3-promoter. The potential coding capacity of P3-RNA is discussed.

Alleles↗
PubMed1988

TPA-inducible Epstein-Barr virus genes in Raji cells and their regulation.

A number of agents including the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) can induce an abortive virus cycle in the EBV nonproducer Burkitt's lymphoma line Raji. We describe the pattern of viral RNAs transcribed in uninduced cells and in cells treated with TPA for 8 hr, as analyzed by Northern blotting. By comparing the patterns of RNAs observed in cells treated with TPA, TPA plus cycloheximide, or cycloheximide alone, we have tested whether any EBV gene in TPA-treated Raji cells would be inducible directly by TPA in the presence of protein synthesis inhibitors, similarly to immediate-early genes induced by superinfection of Raji cells with P3HR-1 virus in the presence of cycloheximide. We demonstrate here that induction of all early EBV genes is dependent on ongoing protein synthesis. The experiments do not provide an answer to whether TPA acts by activating an initial step in the cascade of virus production or whether TPA has a simultaneous pleiotropic effect on the regulation of a large number of viral genes.

Genes, Viral↗
PubMed1988

The block of elongation in c-myc exon 1 is abolished in Burkitt's lymphoma cell lines with variant translocation.

Dimethylsulfoxide (DMSO) induces a block of c-myc RNA elongation in the human B cell line BJAB. In Burkitt's lymphoma cell lines with variant translocations, which are characterized by mutations in and around the first c-myc exon, DMSO is not capable of inducing the RNA elongation block. The action of DMSO is, however, not restricted to regulation at the level of RNA elongation. In the cell line BL2 with a t(8;22) translocation c-myc steady-state RNA decreased about 20 fold 1 and 2 h after DMSO treatment, followed by an increase to approximately initial levels after 4 h. During the time course of the experiment the usage of the dual promoter P1/P2 shifted from the ratio 3:1 in untreated cells to the ratio of 1:5 in BL2 cells treated with DMSO for 4 h. This promoter shift is presumably regulated at the transcriptional level. In BJAB cells an isolated intragenic transcription was detected at the boundary of intron 1 and exon 2. This transcription appeared 2 to 4 h after addition of DMSO when expression of the c-myc gene was downregulated by blocking RNA elongation at the end of exon 1.

Blotting, Southern↗
PubMed1987

Truncation does not abrogate transcriptional downregulation of the c-myc gene by sodium butyrate in Burkitt's lymphoma cells.

We have examined the effect of sodium butyrate, a potent inducer of differentiation in various cell systems, on the steady state RNA level and transcriptional activity of the c-myc gene in Burkitt's lymphoma cells. Following sodium butyrate treatment a rapid decrease of c-myc RNA was observed in all Burkitt's lymphoma cell lines studied, irrespective of the type of translocation, the location of the breakpoint relative to c-myc or of the association with EBV. Since cellular genes induced by interferon are suspected to play a role in c-myc regulation we have studied transcription of the 2-5A synthetase gene in sodium butyrate-treated Burkitt's lymphoma cells. Transcriptional activity and steady state mRNA levels of the 2-5A synthetase gene were induced by sodium butyrate. The time course of induction excluded, however, that the decrease of c-myc RNA is caused by induction of the 2-5A synthetase/RNase L endonuclease system. The reduction of c-myc RNA is caused, at least in part, by a reduced transcription rate, as shown by nuclear run-on analysis. The fact that sodium butyrate is capable of downregulating a truncated c-myc gene indicates that an important target site of transcriptional regulation is located outside the region encompassing the upstream regulatory sequences, the dual promoters and the leader region.

2',5'-Oligoadenylate Synthetase↗
PubMed1987

Electron microscopy of binding of Epstein-Barr virus (EBV) nuclear antigen (EBNA-1) to EBV DNA.

Specific binding sites for Epstein-Barr virus (EBV) nuclear antigen (EBNA-1), isolated and semipurified from EBV-transformed nonproductive Raji cells, were visualized on the molecule of EBV DNA by electron microscopy and mapped. Two measures had to be applied to counteract the limited purity of the EBNA-1 preparation: (i) EBV DNA/EBNA-1 complexes were specifically enlarged by binding with anti-EBNA-1 (IR-3) IgG antibody. (ii) DNA-binding proteins that did not react with the anti-EBNA-1 antibody were eluted from EBV DNA with 1.5 M NaCl, taking advantage of the resistance of DNA/EBNA-1/anti-EBNA-1 antibody complexes to the high-salt treatment. EBNA-1 bound at the highest relative frequency (greater than 30%) to the EBV DNA map positions of 8.8 +/- 0.3, 10.3 +/- 0.5, and 46.6 +/- 1.2 kb. It bound with a lower but still statistically significant frequency (16%) to the map positions of 64.5 +/- 1.0, 89.7 +/- 1.6, 129.6 +/- 1.1 kb.

Antigens, Viral↗
PubMed1987

[Chromosome translocations and Epstein-Barr virus in Burkitt's lymphoma].

Burkitt's lymphoma is characterized by particular epidemiological features. It is a frequent childhood tumor in children in tropical Africa and occurs at a much lesser frequency all over the world. Chromosomal translocation affecting the long arm of chromosome 8 (band 8q24) and one of the chromosomes carrying the immunoglobulin loci (chromosomes 2, 14 or 22) are regularly observed in Burkitt's lymphoma, regardless of whether the tumor occurred in high or low incidence areas. The prevalence of Burkitt's lymphoma in Africa appears to be related to two factors: holo- or hyperendemic malaria and presence of Epstein-Barr virus genomes in the tumor cells. We present a model of pathogenesis, in which stimulation of B cells by malaria is the primary event in the development of the disease. The risk of the chromosomal translocation should be increased by increasing the number of new B cells generated per time. According to our model, the translocation leads to constitutive c-myc activation and makes the cells responsive to growth factors without inducing proliferation on its own. Infection of a translocation-carrying cell with EBV may provide an additional growth advantage and drive the cell further towards a fully malignant state.

Burkitt Lymphoma↗
PubMed1987

Transcription of c-myc in human mononuclear cells is regulated by an elongation block.

Human mononuclear cells (MNC) isolated from tonsils express very low amounts of c-myc RNA. High expression of the c-myc gene is achieved by stimulation of MNC with pokeweed mitogen (PWM). Nuclear run-on transcription experiments revealed activation of the c-myc gene on the transcriptional level. In unstimulated cells a high transcriptional activity is observed on exon 1, but not on exon 2 and 3. After PWM stimulation, however, a high transcription rate is detected on the entire c-myc gene. Therefore, we conclude that c-myc gene expression in MNC is regulated by an RNA elongation block within the first exon. The analysis of the c-myc chromatin structure revealed that DNAaseI hypersensitive site II upstream of the gene is present in unstimulated as well as stimulated MNC, indicating that accessibility of this site is an essential but not sufficient requirement for c-myc gene expression.

Cell Nucleus↗
PubMed1986

Nucleic acid hybridization for detection of herpes viruses in clinical specimens.

A diagnostic hybridization assay for detecting varicella zoster virus (VZV), herpes simplex virus (HSV), and Epstein-Barr virus (EBV) in different clinical specimens was developed using cloned viral DNAs as probes. All probes detected at least 5 pg of homologous DNA and did not cross-react with other viral or cellular DNA. Results of cell culture, serology, and DNA assay were highly concordant. Using a simple standardized protocol for preparation of specimens, hybridization, and washing procedures, this sensitive and specific assay appears to be useful for screening clinical specimens and may be helpful in confirming the serological diagnosis of HSV encephalitis and persistent EBV infections or EBV-associated diseases.

Adult↗
PubMed1984

Two deletions in the Epstein-Barr virus genome of the Burkitt lymphoma nonproducer line Raji.

The Epstein-Barr virus genome carried in the Burkitt lymphoma nonproducer cell line Raji was characterized by partial denaturation mapping and by hybridization of cloned viral fragments to filters containing separated Raji DNA fragments. Partial denaturation mapping revealed that the EBV DNA population of Raji cells is homogeneous and that two deletions are observed in distant parts of the genome compared to linear DNA isolated from virus particles of different strains. These deletions were characterized by blot analysis. One deletion of 3.15 kb lies within HindIII-E; the second is 2.4 kb and is located close to the right terminus of linear viral DNA. The two deletions were observed in several cell lines derived from the Raji line. These deletions might contribute to the inability of Raji cells to produce EBV either spontaneously or upon induction.

Burkitt Lymphoma↗
PubMed1984

A complete set of overlapping cosmid clones of M-ABA virus derived from nasopharyngeal carcinoma and its similarity to other Epstein-Barr virus isolates.

DNA of the transforming, nondefective Epstein-Barr virus (EBV) strain M-ABA, which is derived from nasopharyngeal carcinoma cells, was cloned as large overlapping pieces into the cosmid pHC79 . The termini were cloned from closed circular virus DNA molecules out of M-ABA cell DNA in phage lambda L47 . The large overlapping clones were used to prepare a library of subclones with inserts of 1-15 kb. A detailed restriction enzyme map of M-ABA virus DNA reveals the close similarity to isolates from other sources. The high number of tandem repeats in EBV DNA stresses the importance of using cloning vectors that can be propagated in recA- Escherichia coli hosts.

Carcinoma↗
PubMed1984

Expression of a nuclear and a cytoplasmic Epstein-Barr virus early antigen after DNA transfer: cooperation of two distant parts of the genome for expression of the cytoplasmic antigen.

Expression of Epstein-Barr virus (EBV) antigens was studied after transfection of cloned EBV DNA fragments into baby hamster kidney (BHK) cells. A set of seven widely overlapping clones covering the whole genome of the non-defective Epstein-Barr virus strain M-ABA was used for transfection. Transfer of the cosmid clones into BHK cells resulted in expression of two distinct antigens, as revealed by indirect immunofluorescence using human anti-EBV sera. Staining with human sera of different reactivity against EBV-associated antigens revealed that both types of antigens were related to the early antigen complex. The first type of antigen was detected only in the nuclei of BHK cells that had received DNA of a clone containing HindIII-G, -H, -E, -I2, -O, -I1, and -P. The second type of antigen was found in the cytoplasm of cells cotransfected with clones containing Sal-A and HindIII-I2, -O, -I1, -P, and -C, whereas transfection of both individual clones failed to induce the antigen. Further analysis with subclones identified HindIII-G (5 kilobases) and HindIII-I2 (3 kilobases) plus the rightmost 3 kilobases of Sal-A as the sequences responsible for expression of the nuclear and the cytoplasmic antigen, respectively. The fact that two distant regions of the viral genome are required for expression of a viral antigen provides evidence for intergenomic regulation that can be studied in vitro.

Animals↗
PubMedDate not supplied

A computer-assisted two-dimensional gel electrophoresis approach for studying the variations in protein expression related to an induced functional repression of NFkappaB in lymphoblastoid cell lines.

Strategies are needed for conclusive interpretation of two-dimensional gel electrophoresis (2-D PAGE) maps in order to identify pertinent differences in protein expression during regulation of the transcription of discrete sets of genes. The model used in this study was a human lymphoblastoid cell line in which a functional repression of the transcription factors NFkappaB was obtained by induction of overexpression of IkappaBalpha, a physiological inhibitor of NFkappaB. The analytical methodology used relies on the comparison of two sets of 2-D PAGE maps for detecting differences in protein expression between samples overexpressing or not overexpressing IkappaBalpha. The analysis was based on a combination of an automatic computerized analysis, constituting an actual aid for deciding, and of an interactive visual validation, corresponding to the interpretation of computer propositions. This strategy is proposed as a rapid way to detect potential variations in protein expression applicable to any biological model. In this study, correspondence analysis data made it possible to discrimate between the samples overexpressing or not overexpressing IkappaBalpha, and pointed out some of the potential meaningful spots characterizing the samples in which NFkappaB was active. Then, after visual validation of the computer data, 53 polypeptides were considered to be different in the two classes of gels. Five polypeptides were specifically found in both samples overexpressing IkappaBalpha. The overexpression of IkappaB also induced a lower expression of 11 polypeptides. Finally, 15 polypeptides were only expressed in samples in which IkappaBalpha was not overexpressed and, consequently, in which NFkappaB factors were active. Thus, these polypeptides are candidates for further analysis as putative target gene products of NFkappaB.

Acrylic Resins↗