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H H Niller

Publications and source records attributed to H H Niller.

16 recordsLinked to original sources
PubMed2004

A 30 kb region of the Epstein-Barr virus genome is colinear with the rearranged human immunoglobulin gene loci: implications for a "ping-pong evolution" model for persisting viruses and their hosts. A review.

The left part of the Epstein-Barr virus (EBV) genome exhibits a strong colinearity of structural and functional elements with the immunoglobulin (Ig) gene loci which is only partially reflected in nucleotide sequence homologies. We propose that this colinearity may be the result of an inter-dependent co-evolution of the immunoglobulin loci together with EBV. Our observation could help elucidating the mechanisms of somatic hypermutation, explaining the ability of EBV to accidentally cause tumors, and shedding more light on the general mechanisms of viral and organismal evolution. We suggest that persisting viruses served as a complement for the organismal germline like in a ping-pong game and outline The Ping-Pong Evolution Hypothesis.

Chromosome Mapping↗
PubMed2001

In vitro activities of six quinolones and mechanisms of resistance in Staphylococcus aureus and coagulase-negative staphylococci.

Of 94 clinical isolates of Staphylococcus aureus (n = 51) and coagulase-negative staphylococci (CNS) (n = 43), mutations in the quinolone resistance-determining region of topoisomerases GrlA, GrlB, GyrA, and GyrB together with MICs of six quinolones were analyzed. Amino acid substitutions at identical residues (GrlA residues 80 and 84; GyrA residues 84 and 88) were found in S. aureus and CNS. Active efflux, as suggested by blocking by reserpine, contributed substantially to the resistance phenotype in some strains. Among ciprofloxacin, clinafloxacin, levofloxacin, nalidixic acid, trovafloxacin, and sparfloxacin, a 0.5-microg/ml concentration of sparfloxacin discriminated best between strains with two or three mutations and those with no mutations.

4-Quinolones↗
PubMed2001

Protein-DNA binding and CpG methylation at nucleotide resolution of latency-associated promoters Qp, Cp, and LMP1p of Epstein-Barr virus.

Epstein-Barr viral (EBV) latency-associated promoters Qp, Cp, and LMP1p are crucial for the regulated expression of the EBNA and LMP transcripts in dependence of the latency type. By transient transfection and in vitro binding analyses, many promoter elements and transcription factors have previously been shown to be involved in the activities of these promoters. However, the latency promoters have only partially been examined at the nucleotide level in vivo. Therefore, we undertook a comprehensive analysis of in vivo protein binding and CpG methylation patterns at these promoters in five representative cell lines and correlated the results with the known in vitro binding data and activities of these promoters from previous transfection experiments. Promoter activity inversely correlated with the methylation state of promoters, although Qp was a remarkable exception. Novel protein binding data were obtained for all promoters. For Cp, binding correlated well with promoter activity; for LMP1p and Qp, binding patterns looked similar regardless of promoter activity.

Burkitt Lymphoma↗
PubMed2001

Epigenetics of latent Epstein-Barr virus genomes: high resolution methylation analysis of the bidirectional promoter region of latent membrane protein 1 and 2B genes.

We analysed the methylation patterns of CpG dinucleotides in a bidirectional promoter region (LRS, LMP 1 regulatory sequences) of latent Epstein-Barr virus (EBV) genomes using automated fluorescent genomic sequencing after bisulfite-induced modification of DNA. Transcripts for two latent membrane proteins, LMP 1 (a transforming protein) and LMP 2B, are initiated in this region in opposite directions. We found that B cell lines and a clone expressing LMP 1 carried EBV genomes with unmethylated or hypomethylated LRS, while highly methylated CpG dinucleotides were present at each position or at discrete sites and within hypermethylated regions in LMP 1 negative cells. Comparison of high resolution methylation maps suggests that CpG methylation-mediated direct interference with binding of nuclear factors LBF 2, 3, 7, AML1/LBF1, LBF5 and LBF6 or methylation of CpGs within an E-box sequence (where activators as well as repressors can bind) is not the major mechanism in silencing of the LMP 1 promoter. Although a role for CpG methylation within binding sites of Sp1 and 3, ATF/CRE and a sis-inducible factor (SIF) cannot be excluded, hypermethylation of LRS or regions within LRS in LMP 1 negative cells suggests a role for an indirect mechanism, via methylcytosine binding proteins, in silencing of the LMP 1 promoter.

CpG Islands↗
PubMed2001

Specific nucleoprotein complexes within adenovirus capsids.

Adenoviral DNA was examined within capsids by dimethyl sulfate footprinting. Protein-DNA interactions were visualized through ligation-mediated PCR (LM-PCR). Signals for protein binding were found adjacent to both inverted terminal repeats (ITR). There were no indications of close protein binding at several other loci of the viral genome. Therefore, adenovirus type 5 seems to contain sequence- or locus-specific DNA binding proteins within the virion.

Adenoviridae↗
PubMed2001

Protein-DNA interaction and CpG methylation at rep*/vIL-10p of latent Epstein-Barr virus genomes in lymphoid cell lines.

The viral interleukin-10 promoter (vIL-10p), overlapping the rep* element in the Epstein-Barr virus (EBV) genome, is a promoter element active mostly in the late phase of the lytic cycle and immediately upon infection of B cells. rep* was, through transfection experiments with small plasmids, characterised as a cis element supporting oriP replicative function. In this study, in vivo protein binding and CpG methylation at rep*/vIL-10p were analysed in five cell lines that harbour strictly latent EBV genomes. Contrary to the invariably unmethylated dyad symmetry element (DS) of oriP, rep*/vIL-10p was highly methylated and showed only traces of protein binding in all examined cell lines. This result is in agreement with vIL-10p being an inactive promoter of EBV genomes, and makes it less likely that rep* functions as a replicative element of latent EBV genomes.

Base Sequence↗
PubMed1998

Regulation of the Epstein-Barr viral immediate early BRLF1 promoter through a distal NF1 site.

The immediate early BRLF1 and BZLF1 promoters of Epstein-Barr virus are crucial for triggering the replicative cycle of the virus. To better understand the cell type dependence of the lytic cycle we conducted an analysis of the BRLF1-promoter in the epithelial cell line HeLa and the lymphoid cell line IM9. To analyze promoter activities, transient transfections with 5'-deletions of the BRLF1-promoter in front of luciferase as reporter gene were conducted. Besides the already known cis-acting elements of the promoter close to the TATA-box, more distal elements were located and functionally tested. A nuclear factor 1 consensus site was found to act positively in HeLa cells, but did not in lymphoid IM9 cells. The NF1 site was shown to bind protein by electrophoretic mobility shift assays, antibody-supershifts and in vitro footprinting. Thus, a protein belonging to the nuclear factor 1 family of proteins was identified as additional cellular trans-acting factor for the BRLF1-promoter besides the already described factors Sp1, Zta and Zif268.

Binding Sites↗
PubMed1995

Nucleoprotein complexes and DNA 5'-ends at oriP of Epstein-Barr virus.

Understanding protein-DNA interactions in vivo at origins of DNA replication throughout the cell cycle may shed further insight on the mechanisms of initiation and replication control. The Burkitt's lymphoma cell line Raji harbors multiple copies of latent Epstein-Barr virus. Once per cell cycle the origin of plasmid replication of Epstein-Barr virus provides replication function in cis for the viral DNA. Here we examined in vivo nucleoprotein complexes on the initiator element of the origin before and after DNA synthesis. For this purpose Raji cells were synchronously growth arrested in G1 phase by mimosine and in mitosis by colchicine, respectively. The association of the initiator element with proteins was visualized by footprinting with dimethyl sulfate and ligation mediated polymerase chain reaction. Methylation patterns indicated a novel binding activity within each element of a nonamer repeated three times at the initiator element. This activity was strongly diminished in mitotic cells. Furthermore, 5'-ends of Epstein-Barr virus DNA were mapped to the nonamers by ligation mediated polymerase chain reaction, suggesting potential initiation sites for replication from DS.

Antigens, Viral↗
PubMed1993

[Epstein-Barr virus].

Epstein-Barr virus is an ubiquitous humanpathogenic herpesvirus. It has been identified as the etiologic agent of infectious mononucleosis. In addition it is associated with the cancers nasopharyngeal carcinoma and Burkitt's lymphoma. Like other herpesviruses it infects cells in a lytic way or it persists in a latent state. Classically, the serologic diagnosis of Epstein-Barr virus infections is done by the agglutination of sheep erythrocytes according to Paul and Bunnell as a rapid testing method, and with the immunofluorescence assay. Lately, also the enzyme linked immunosorbent assay using recombinant viral antigens is used for Epstein-Barr virus diagnostics.

Animals↗
PubMed1992

Characterization of the 5'-flanking region of the rat thyrotropin receptor gene.

Genomic clones containing 1.7 kilobases of the 5'-flanking region of the rat TSH receptor (TSHR) plus coding sequence from the ATG initiation codon [1 basepair (bp)] to the start of the first intron (170 bp) have been isolated and characterized. RNAase protection, primer extension, and cDNA sequences cloned by the anchored polymerase chain reaction identified multiple transcriptional start sites, the major ones clustered between -89 to -68 bp. This portion of the 5'-flanking region has neither a TATA nor a CCAAT box, is GC rich but has no GC box motif, and has features of promoters seen in "housekeeping" genes. Chimeras containing 1.7 kilobases (-1707 to -2 bp) of the 5'-flanking region, or deletions thereof, and the bacterial chloramphenicol acetyltransferase (CAT) gene expressed significant CAT activity when transfected into rat thyroid cell lines, FRTL-5 and FRT, but not BRL rat liver or HeLa cells. TSH decreased CAT activity in the FRTL-5 thyroid cells that had been stably transfected with the TSHR-CAT chimeric constructs. Negative regulation of promoter activity by TSH was duplicated by 10 microM forskolin in FRT thyroid cells, which express no TSHR mRNA. Deletion analyses indicated that a "minimal" region, exhibiting promoter activity, tissue specificity, and negative regulation by TSH, is located between -195 and -39 bp; this region is highly conserved in rat and human TSHR genes. Differential digestion of genomic DNA by MspI and HpaII revealed that the TSHR promoter is methylated in FRT, but not FRTL-5, cells; methylation of the promoter may be associated with loss of endogenous TSHR gene expression in FRT cells.

Amino Acid Sequence↗
PubMed1991

Formation of several specific nucleoprotein complexes on the human cytomegalovirus immediate early enhancer.

The major immediate early enhancer of the human cytomegalovirus (HCMV) is composed of unique and repeated sequence motifs, which interact with different nuclear proteins, thus forming a large nucleoprotein complex. Using DNAase I protection analysis, we determined at the nucleotide level the interactions of B cell and HeLa cell nuclear proteins with transcription factor binding sites in the enhancer/promoter. In agreement with in vivo activity, protein binding to the 18 bp repeats (kappa B element) was found predominantly with B cell extract. Competition for proteins with individual transcription factor binding sites allowed us to define boundaries of closely spaced and overlapping binding sites, and to group binding proteins into several classes. Using gel mobility shift assays, we could show that proteins, which bind to the 17 bp repeat, also bind to a classical NF1 site. In addition, several novel binding sites were identified. The presence of overlapping binding sites, together with differences in the occupation of the 18 bp repeats in the two cell types, suggest that the HCMV major IE enhancer has several possibilities of forming nucleoprotein complexes.

B-Lymphocytes↗
PubMed1990

Phytohemagglutinin-induced activity of cyclic AMP (cAMP) response elements from cytomegalovirus is reduced by cyclosporine and synergistically enhanced by cAMP.

The 19-base-pair enhancer repeat of the human cytomegalovirus immediate-early 1 gene mediates cyclic AMP- and phytohemagglutinin-induced expression in Jurkat T cells. Synergistic activity was observed in the presence of both drugs, suggesting a convergence of the protein kinase A and C pathways on this transcription element. In addition, the immunosuppressive drug cyclosporine strongly reduced the ability of the 19-base-pair repeat to activate gene expression in phytohemagglutinin-stimulated T cells.

Base Sequence↗
PubMed1986

The A+T-rich genome of Herpesvirus saimiri contains a highly conserved gene for thymidylate synthase.

Herpesvirus saimiri (HVS) is the prototype member of a distinctive subset of lymphotropic herpesviruses (the gamma 2 subgroup) with A+T-rich coding sequences. In this paper, we show that cells productively infected with HVS contain high concentrations of a virus-specified thymidylate synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 2.1.1.45); we identify the active polypeptide and present the sequence of the virus gene. The predicted amino acid sequence of the 294-residue subunit of the virus enzyme is 70% homologous with the sequence of the human enzyme and about 50% homologous with prokaryotic thymidylate synthases, illustrating the remarkable structural constraints imposed by the thymidylate synthase function. However, the presence of the enzyme is not a conserved property of herpesviruses. We find no evidence for a virus-encoded thymidylate synthase activity (or a homology to a thymidylate synthase sequence) in G+C-rich representatives of alpha 1 (e.g., herpes simplex viruses, 66-68% G+C), beta (i.e., human cytomegalovirus, 58-59% G+C), and gamma 1 (i.e., Epstein-Barr virus, 60% G+C) herpesvirus subgroups. The production of excess thymidylate by a virus thymidylate synthase in cells infected with an A+T-rich herpesvirus would provide one plausible source of biased mutations by the virus-encoded replicative enzymes, which we have previously suggested as the likely general cause of differences in the mean nucleotide compositions of herpesvirus genomes.

Amino Acid Sequence↗
PubMed1986

Organization of the thymidylate synthase gene of herpesvirus saimiri.

Herpesvirus saimiri codes, unlike most other herpesviruses, for a thymidylate synthase (TS). The TS gene of herpesvirus saimiri is unusual in structure and regulation of expression. It is transcribed into a nonspliced mRNA of 2,190 nucleotides. The single open reading frame of the viral TS gene, instructing a polypeptide of 33.5 kilodaltons, has extensive sequence homology with the corresponding TS coding sequences of human cells and of various procaryotes; the putative polypeptide derived from the nucleotide sequence of the herpesvirus saimiri TS gene is 70% identical with the human enzyme. The untranslated regions of the herpesvirus saimiri TS gene do not share homology with the other characterized eucaryotic or bacterial TS genes. The 5' untranslated sequence has 22 ATG triplets shortly followed by stop codons. The herpesvirus saimiri TS gene, which may be weakly transcribed during immediate early and early times of virus replication, is maximally expressed at the late phase. Various parameters suggest that the TS gene has been acquired in virus evolution by an ancestral herpesvirus from the cellular genome.

Amino Acid Sequence↗
PubMedDate not supplied

Decreased T cell stimulatory capacity of monocyte-derived human macrophages following herpes simplex virus type 1 infection.

Macrophages play a central role in establishing a specific immune response by acting as professional antigen presenting cells (APC) for T cells leading to a vigorous immune response. In order to analyze if Herpes simplex Virus (HSV) type 1 infection might affect the macrophage APC-function, monocyte-derived human macrophages were infected with HSV-1 strain F in vitro. Cocultures with allogeneic T cells revealed a strongly impaired stimulatory capacity of HSV-infected macrophages compared to uninfected controls which was not owing to a productive viral infection in macrophages. An increased expression of Fas ligand (FasL/CD95L) was detected in HSV-infected macrophages by FACS analysis. Although the majority of the macrophages expressed high levels of Fas (CD95/Apo-1), the HSV-induced upregulation of FasL did not result in an increased autocrine apoptosis of macrophages which might be related to endogenous expression of the apoptosis inhibitor FLICE inhibitory protein (FLIP). However, substantial apoptosis occurred in peripheral T cells as well as Fas-sensitive Jurkat T cells when cocultured with HSV-infected macrophages. These findings suggest that the paracrine killing of activated T cells by FasL expressing APC might be a novel strategy of immune evasion by HSV.

Apoptosis↗