Design of artificial transcription factors to selectively regulate the pro-apoptotic bax gene.

The tumor suppressor p53 is the most commonly mutated gene in human cancers. Active p53 is able to stimulate the transcription of a variety of genes including the pro-apoptotic gene bax, as well as p21, a cell cycle regulator. In this study we produced novel zinc finger transcription factors that would selectively increase the expression of bax, but not of other p53 targets. Reporter gene assays in p53-negative Saos-2 cells showed that the novel zinc finger proteins stimulated transcription driven by a minimal bax promoter, but not that driven by a minimal p21 promoter. Moreover, electromobility shift assays demonstrated that the novel transcription factors could bind the bax promoter sequence with high affinity and selectivity. Expression of a five zinc finger protein (5ZFAV) in COS-7 cells resulted in an increase in Bax protein levels, indicating that this novel transcription factor could act on endogenous gene expression. Expression of 5ZFAV also drastically reduced Saos-2 cell survival; this effect could be reversed by the general caspase inhibitor B-D-FMK. These data suggest that 5ZFAV is able to induce apoptosis through increased Bax expression. Further, while expression of 5ZFAV in p53-deficient Saos-2 cells reduced cell survival, there was little effect on U-2 OS cells which have wild-type p53. Thus the selective induction of the pro-apoptotic bax gene may be a valuable adjunct to cancer chemotherapy by diminishing survival of p53-deficient tumor cells.

Oxygen and Nitrate Respiration in Streptomyces coelicolor A3(2).

Streptomyces species belong to the phylum Actinobacteria and can only grow with oxygen as a terminal electron acceptor. Like other members of this phylum, such as corynebacteria and mycobacteria, the aerobic respiratory chain lacks a soluble cytochrome c. It is therefore implicit that direct electron transfer between the cytochrome bc1 and the cytochrome aa3 oxidase complexes occurs. The complex developmental cycle of streptomycetes manifests itself in the production of spores, which germinate in the presence of oxygen into a substrate mycelium that greatly facilitates acquisition of nutrients necessary to support their saprophytic lifestyle in soils. Due to the highly variable oxygen levels in soils, streptomycetes have developed means of surviving long periods of hypoxia or even anaerobiosis but they fail to grow under these conditions. Little to nothing is understood about how they maintain viability under conditions of oxygen limitation. It is assumed that they can utilise a number of different electron acceptors to help them maintain a membrane potential, one of which is nitrate. The model streptomycete remains Streptomyces coelicolor A3(2), and it synthesises three nonredundant respiratory nitrate reductases (Nar). These Nar enzymes are synthesised during different phases of the developmental cycle and they are functional only under oxygen-limiting (<5% oxygen in air) conditions. Nevertheless, the regulation of their synthesis does not appear to be responsive to nitrate and in the case of Nar1, it appears to be developmentally regulated. This review highlights some of the novel aspects of our current, but somewhat limited, knowledge of respiration in these fascinating bacteria.

Uptake of [3H] thymidine and cell DNA synthesis during the early multiplication phase of herpesvirus hominis in BHK cells.

Experiments about the interaction of herpes viruses with BHK-cells during the first 6 h after infection concerning uptake and incorporation of dThd have been reported. During adsorption and penetration, the inhibition of uptake and of incorporation of [3H] dThd is sensitive to heat, but not to ultraviolet irradiation or cycloheximide. The eclipse is characterized by a strongly increased uptake of [3H] dThd and by inhibition of cell DNA synthesis. Both are sensitive to ultraviolet irradiation of the particles and cycloheximid treatment of the cells. It is concluded that the events during adsorption and penetration are dependent on the particles themselves, whereas the events during the eclipse depend on the activity of the viral genome. The implications of the findings are discussed.

Influence of dibutyryl cyclic AMP on thymidine uptake by herpes simplex virus infected cells and the intracellular level of cyclic AMP.

Dibutyryl cyclic AMP inhibits the increase of dThd and BrdUrd transport normally observed after infection with Herpesvirus hominis, type I and II. Incorporation is also reduced. Inhibition of uptake is non-competitive as analysed by the Lineweaver-Burk plot. Addition of this drug to infected cells also reduces the activity of the thymidine kinase (EC 2.7.1.75). Transport of dUrd, dCyd and dAdo is not reduced. 4--8 h after infection with thymidine kinase (+) herpes strains the level of cAMP increases. On infection with a thymidine kinase (-) virus, only a small elevation of cAMP can be shown. It was also found that early addition of actinomycin D or of cycloheximide prevents the increase of the cAMP level. This increase seems to depend on the activity of the herpes genome, because ultraviolet irradiation of infective particles destroys this ability.

Alkaline phosphodiesterase I and alkaline phosphatase I in plasma membranes of herpes simplex virus type 1 transformed hamster cells.

Plasma membrane extracts from Herpes simplex virus type 1 transformed hamster embryo fibroblasts were chromatographed on Lens culinaris lectin coupled to Sepharose (LcH-Sepharose) and analysed by dodecyl sulphate polyacrylamide gel electrophoresis. Coomassie blue-staining revealed two major protein bands with apparent molecular weights of 125 000 and of about 75 000-90 000. In plasma membranes isolated from these tumor cells prior labeled with [3H]fucose or [3H]glucosamine these bands contained the highest amounts of incorporated radioactivity. Separation by LcH-Sepharose-affinity chromatography as well as metabolic labeling clearly demonstrates their glycoprotein character. The 125 000 protein coincides with alkaline phosphodiesterase I activity with a Km of 6 . 10(-4) M for TMP p-nitrophenyl ester and is competitively inhibited by UDP-N-acetylglucosamine. This enzymatic activity is also present in normal hamster embryo fibroblasts. Gel electrophoresis of the Lens culinaris lectin-binding glycoproteins from plasma membranes of normal hamster embryo fibroblasts additionally revealed a strong alkaline phosphatase activity represented by an apparent molecular weight of 150 000, while HSV1 hamster tumor cells contain only a very weak activity of this enzyme activity. HSV-lytically infected cells, however, have unchanged levels of alkaline phosphatase activity, whereas alkaline phosphodiesterase activity increases slightly.

Selective transcription of p53 target genes by zinc finger-p53 DNA binding domain chimeras.

Active p53 stimulates the transcription of a number of key genes, including the pro-apoptotic gene bax, as well as p21, a cell cycle regulator. In this study we constructed novel chimeric zinc finger-p53 DNA binding domain (DBD) transcription factors designed to bind to the promoters of specific p53 regulated genes. In order to selectively increase the expression of Bax, we coupled a pre-selected three-zinc finger (Zif) peptide targeted to a sequence in the bax promoter to a minimal p53 DBD. This chimeric protein could increase reporter gene transcription from a minimal bax promoter (up to 10-fold) but not from a minimal p21 promoter in p53-deficient Saos-2 cells. However, fusion proteins carrying longer p53 DBDs displayed entirely different selectivity and potency. Thus, Zif-p53 DBD chimeras containing N- and C-terminal extensions of the minimal DBD could increase transcription driven by a minimal p21 promoter up to 800-fold. These chimeras preferred the minimal p21 promoter up to 500-fold over the minimal bax promoter. Additionally, endogenous p21 message and protein levels were increased in cells expressing the p21 selective Zif-p53 DBD chimera and expression of the chimeric proteins resulted in partial cell cycle arrest. Cell fractionation experiments indicated that the Zifs enhanced nuclear localization of the Zif-p53 DBD chimera. These studies suggest that it is possible to create chimeric transcription factors able to strongly and selectively activate genes downstream of p53.

Differential and selective inhibition of cellular and herpes simplex virus DNA synthesis by arabinofuranosyladenine.

The influence of 9-beta-D-arabinofuranosyladenine (beta araAdo) and of its anomer 9-alpha-D-arabinofuranosyladenine (alpha araAdo) was studied in non-infected cells and cells infected with herpes simplex virus type 1 (HSV-1) and HSV type 2 (HSV-2). alpha AraAdo is a strong inhibitor of proliferation of non-infected cells. Multiplication of HSV-1 and HSV-2 is not affected at all by alpha araAdo, while their growth is strongly inhibited by beta araAdo. alpha AraAdo exerts no effect on the incorporation of dThd into HSV DNA, but blocks the incorporation into host cell DNA. Its anomer, beta araAdo, affects the incorporation rate of both the viral DNA system and the host cell DNA system (the latter one to a lesser extent). alpha AraAMP is incorporated into newly synthesized cellular DNA but not into HSV DNA. Enzymic studies relevant that alpha araATP has no effect on the HSV DNA polymerase system but a high inhibitory potency in the host cell DNA polymerase alpha system. The anomeric form, beta araATP, is a sensitive inhibitor of HSV DNA polymerase while the cellular DNA polymerases alpha and beta are more refractory.

Adenosine diphosphate: thymidine 5'-phosphotransferase, a new enzyme activity, associated with the Herpes simplex virus-induced deoxypyrimidine kinase.

The deoxypyrimidine kinase induced in mouse fibroblasts, strain CLID (TK-) infected with either herpes simplex virus (HSV) type 1 or type 2, possesses besides deoxypyrimidine kinase (ATP:dThd/dCyd phosphotransferase) two further enzyme activities: an AMP:dThd phosphotransferase and an ADP:dThd phosphotransferase. The latter enzyme activity, described in this report, was found to be inhibited by antiserum against the HSV deoxypyrimidine kinase and to be absent after infection with TK- mutant MDK 10 (B 2006). The ADP:dThd phosphotransferase, which had been purified approx. 340-fold, differs by a series of physicochemical properties from the viral AMP:dThd- and ATP:dThd phosphotransferase.

Change of processing and nucleocytoplasmic transport of mRNA in HSV-1-infected cells.

A monoclonal antibody (MAb) raised against the pore-complex lamina fraction from CV-1 cells was used to study alterations of gene expression in herpes simplex virus type 1 (HSV-1)-infected cells. This MAb, which recognized only one cellular polypeptide of 60,000 Da, selectively stained the nucleus in immunofluorescence microscopy, showing a punctuated pattern either at the nuclear surface or at the nuclear rim. By immunoelectron microscopy, the p60 antigen could be localized in the nuclear pore complex structure. Infection of CV-1 cells with HSV-1 resulted in a drastic change of the nuclear staining pattern. Four hours p.i., a clustering of the p60 antigen and, 12 h p.i., a formation of finger-like holes, penetrating the nucleus, occurred. Later in infection (22 h p.i.) the antigen was found to be almost absent. By RNA blot hybridization it was demonstrated that, after HSV-1 infection, the level of cellular mRNA (beta-tubulin) gradually decreased, while the level of HSV major DNA binding protein (DBP) mRNA increased, reaching maximal level 3-6 h p.i. Interestingly, the level of beta-tubulin gene transcripts changed differentially in the polysomal and in the nuclear fraction during the initial phase of infection, in contrast to the viral DBP transcripts, indicating that, after HSV infection, host cell transcripts accumulate in the nucleus. Evidence is presented indicating that this change is not due to altered nucleocytoplasmic mRNA transport but is due to an impaired splicing of host cell transcripts in HSV-infected cells. The MAb, directed against the nuclear pore p60 antigen, strongly inhibited the ATP-dependent efflux of both cellular and viral mRNA from isolated nuclei. The ATP-dependence of the efflux did not change during viral infection. However, the inhibitory potency of the MAb was found to be lost at the final stage of HSV infection, paralleling the loss of p60 antigen.

Identification and properties of the cell membrane bound leucine aminopeptidase interacting with the potential immunostimulant and chemotherapeutic agent bestatin.

Bestatin was found to be a competitive inhibitor (with respect to the Leu-NA substrate) not only of the isolated microsomal and cytosolic leucine aminopeptidases (Leu-APm and Leu-APc) but also of the aminopeptidases (APs) present in membrane preparations (from mouse liver) and on the cell surface of L5178Y cells. Kinetic parameters indicate that cellular AP is identical to Leu-APm. To rule out the possibility that AP-B is involved in the inhibition reactions, comparable studies with amastatin were performed. Electrophoretical studies revealed the solubilized cell membrane bound AP to co-migrate with Leu-APm in polyacrylamide gels. The activity of the separated membrane AP was inhibited by bestatin in situ. The cell membrane bound AP activity was found to be lowest in lymphocytes, higher in tumor cells and highest in bone marrow cells and macrophages. Using synchronized L5178Y cells, the AP activity changes during the cell division cycle; the lowest activity was determined during the G1-phase and 35% higher values were measured during the S/G2-phase. The fluctuation of the cell surface associated AP activity parallels with changes in the number of binding sites for bestatin.

Translocation of the nuclear autoantigen La to the cell surface of herpes simplex virus type 1 infected cells.

Recently we developed a procedure to translocalize one of the extractable nuclear antigens (ENAs), the La protein, to the cell surface of CV-1 cells. Here we report that herpes simplex virus type 1 infection can also induce a translocation of the autoantigen to the cell surface. On the cell surface we detected La protein assembled with large protrusions. Within these protrusions La protein colocalized with virus particles. These protrusions are known to be released from the cell after virus infections. Such complexes consisting of self and virus could provide helper determinants for an anti-self response, and therefore be important in generation of autoimmunity.

Axonal and transsynaptic (transneuronal) spread of Herpesvirus simiae (B virus) in experimentally infected mice.

In order to study the pathogenesis of B virus infection of the nervous system, newborn and young mice were inoculated by four different routes: 1. Intramuscular (i.m.) in the forelimb; 2. I.m. in the hindlimb; 3. Subcutaneous (s.c.) in the abdominal wall; 4. Intraperitoneal (i.p.). Spread of virus was followed by immunohistochemical demonstration of viral antigen in tissue sections of the peripheral and central nervous system. Three distinct patterns emerged: 1. After i.m. limb inoculations, virus progressed along the ipsilateral dorsal column, the bilateral spinothalamic and bilateral spinoreticular systems and along central autonomic pathways. 2. After s.c. inoculation, the dorsal column was spared, otherwise the spread was similar to that following i.m. inoculations. 3. After i.p. inoculation, virus spread in the spinal cord bilaterally, mainly along spinothalamic and central autonomic pathways. The peripheral motoneurons were conspicuously spared, even in the i.m. inoculation mode. In the brain stem, B virus antigen appeared bilaterally, at multiple sites. In the cerebrum, virus infected cells appeared first in the thalamus, hypothalamus and the motor cortex. The mode of spread from spinal levels was mainly orthograde along the ascending systems (dorsal columns, spinothalamic, spinoreticular tracts), but also retrograde along descending systems (pyramidal tract, central autonomic pathways). Oligosynaptic systems transmitted virus more quickly than the polysynaptic ones. In the involvement of various neuronal systems in virus spread, a certain selectivity, sparing the peripheral motoneuron and the cerebellar systems, could be assessed.

Inhibition of herpesvirus DNA synthesis by 9-beta-D-arabinofuranosyladenine in cellular and cell-free systems.

9-beta-D-Arabinofuranosyladenine 5'-triphosphate (ara-ATP) is an inhibitor both of DNA polymerase-alpha and -beta from noninfected rabbit kidney cells and of the DNA-dependent DNA polymerase induced by herpes simplex virus Type 1 (strain IES). The studies were performed with partially purified enzymes, and each of the different polymerase preparations contained only one DNA-dependent DNA polymerase species. These enzymes were inhibited in a competitive manner. The HSV-induced DNA-dependent DNA polymerase was 39-fold more sensitive to ara-ATP than was cellular DNA polymerase-beta and 116-fold more sensitive than cellular DNA polymerase-alpha. The affinity of the HSV-induced enzyme for ara-ATP was only slightly influenced by the use of different template/initiators in the enzyme assays. In intact cell systems DNA synthesis was affected by 9-beta-D-arabinofuranosyladenine (ara-A) as indicated by the reduced incorporation of deoxythymidine. In herpesvirus-(strain Lennette)-infected cells, however, ara-A shows no influence on the incorporation on deoxythymidine into cellular DNA, but it substantially reduces the incorporation into viral DNA. Ara-A itself is incorporated into both cellular and herpesviral (strain Lennette, D-316 and IES) DNA during DNA synthesis.

Vaginal infection of mice with HSV type 2 variant ER-: a new animal model for human primary genital HSV type 2 infections.

Studying the pathogenesis of vaginal infections in mice with two variants of Herpes simplex virus type 2 (HSV-2) strain ER we observed that both variants ER+ and ER- caused severe vaginitis but only ER+ invaded the CNS leading to lethal neurological disease. In contrast, mice infected with ER- cleared the virus from the vagina and recovered from infection. ER+ and ER- expressed equal levels of thymidine kinase (TK) indicating a TK-independent difference in neurovirulence. Using the non-neurovirulent variant ER-, we were able to investigate humoral immune responses later after infection. Vaginal infection with ER- suppressed serum antibody formation after a secondary systemic HSV-1 infection. Fresh isolates of HSV-1 and HSV-2 caused uniformly a lethal neurological disease after vaginal inoculation of mice. However, some animals survived an intraperitoneal infection with these isolates. Infection with HSV-1 isolates stimulated a strong antibody production, whereas infection with HSV-2 isolates suppressed antibody formation, thus supporting earlier results from our group obtained with laboratory strains. Since suppression of antibody formation could be demonstrated with clinical HSV-2 isolates and likewise after vaginal infection with HSV-2 variant ER- we consider this phenomenon to be of relevance in human genital HSV-2 infections. Vaginal infection of mice with variant ER- represents a new model for primary genital HSV-2 infections; this model could be useful for histopathological, virological, immunological and drug testing studies.

TNF-alpha mediated apoptosis of CD4 positive T-lymphocytes. A model of T-cell depletion in HIV infected individuals.

Apoptosis has been suggested to account for loss of CD4+ T-cells in HIV infected individuals. Aside from MHC II dependent superantigens no mediator for preferential apoptosis of CD4+ T-cell has been described. However, the expression of TNF-alpha is increased in HIV+ patients. Additionally, TNF-alpha is known as a potent inducer of apoptosis in a variety of cell types. We therefore investigated the capacity of TNF-alpha to mediate apoptosis in vitro preferentially in CD4+ T-cells from HIV+ individuals. In the presence of TNF-alpha, CD4+ T-cells from HIV+ individuals with more than 200 CD4+ T-cells/microl (classified CDC A1, A2, B1, B2) could be significantly depleted by apoptosis without a reduction of CD8+ T-cells. In cells from patients with less than 100 CD4+ T-cells/microl (classified CDC C3), TNF-alpha mediated apoptosis was not apparent due to an already immensely elevated rate of apoptosis observed in the absence of TNF-alpha. Here we demonstrate cord blood mononuclear cells as a model for apoptosis since these cells develop apoptosis at a similar rate as that of PBMC in HIV+ patients. More than 50% of TNF-alpha stimulated CD4+ cord blood T-cells were depleted within 3 days by apoptosis, whereas CD8+ T-cells, B-cells and NK-cells were not affected. In PBMC from healthy adults, a preferential loss of CD4+ T-cells mediated by TNF-alpha was not observed. A reduced production of IFN-gamma was observed in mononuclear cells from newborns and from HIV+ patients. Moreover, IFN-gamma and IL-2 could prevent TNF-alpha mediated apoptosis. Therefore, a reduced Th1-cell-function may contribute to TNF-alpha mediated apoptosis of CD4+ T-cells from these donor groups. Taken together, the data suggest that TNF-alpha probably is a mediator of the loss of CD4+ T-cells in HIV infected patients in vivo.

[Is type I diabetes a virus-induced disease?]. / Ist der Typ-I-Diabetes eine virusbedingte Erkrankung?

The conditions are critically reviewed under which diseases might be aetiologically related to infection by a certain virus. Such a causal correlation has to obey Koch's postulates, but may be very difficult to prove in the case of a "hit and run" process. This will be exemplified in the case of insulin-dependent diabetes mellitus (IDDM). Observations in humans and the results of experiments on laboratory animals are reported, whereby the Coxsackie B and mumps viruses are of particular interest. Furthermore, the mechanisms by which viruses may produce autoimmune diseases are discussed, including virological and immunological aspects. The hypothesis of "molecular mimicry" by Oldstone is quoted as a unifying one, allowing the combination of both aspects. His main assumption is oligopeptide homology between certain virus proteins and some cell proteins and some examples are given. In the presence of such homologies the immune system is first stimulated by the parasitic virus protein, but somewhat later this reaction switches against the host structures, causing continuing cellular damage with the development of autoimmune disease. It is concluded that Koch's postulates in such cases have to be supplemented by assaying for amino acid homologies in viruses and certain cell types.

Biochemical classification of herpes simplex virus types 1 and 2, and of intermediate strains on the basis of different susceptibilities of thymidine kinase to thymidine analogues.

Herpes simplex virus (HSV) type 1 can be differentiated from HSV type 2 on the basis of the sensitivity to 2'-deoxythymidine-5'-monophosphate of thymidine kinase induced in primary rabbit kidney cells. Whereas thymidine kinase induced by five strains of HSV type 1 (TK 1) is stimulated by suitable concentrations of 2'-deoxythymidine-5'-monophosphate, thymidine kinase induced by eight strains of HSV type 2 (TK 2) is inhibited. On the other hand, TK 2 is strongly inhibited by 2'-deoxythymidine-5'-triphosphate and by 2-bromo-2'-deoxyuridine-5'-triphosphate. The investigation of TK induced by six freshly isolated strains of HSV cross-reacting in neutralisation tests revealed two strains which induced TK 1 and two strains which induced TK 2. Two other strains induced thymidine kinase, the activity of which under the influence of these thymidine analogues was between that of TK 1 and TK 2. The properties of thymidine kinase remained constant after cloning the virus and thus is a genetically fixed trait due to recombination which could well occur in vivo.

Influence of glycoproteins B, C and D on the conversion of virus-to-cell attachment from heparin sensitivity to resistance.

Glycoprotein C-negative (gC-) mutants of herpes simplex virus type 1 (HSV-1) derived from strains KOS and ANGpath were used to analyse the influence of soluble heparin on the phase of adsorption/attachment of HSV-1 to cells. A dose of 200 micrograms/ml heparin given 20 mins after infection of cells with the gC- positive (gC+) strains KOS and ANGpath at 4 degrees C reduced the adsorption of infective particles to 20-30% of the controls. A weaker heparin effect was observed with gC- mutants. However, also the gC- mutants exhibited a short heparin-sensitive phase. Mutations in amino acids of gB or gD at positions 854 or 25 and 27, respectively, did not alter the attachment capacities of these HSV mutants in the presence of heparin despite their peculiar fusion properties and resistance to soluble gD. We conclude that HSV-1 strains exhibit a heparin-resistant phase of attachment, which is determined by gC. Lack of gC delays the heparin-resistant attachment phase of HSV-1 to cells.

Multiplication of herpes simplex virus types 1 and 2 in macrophages of NMRI and C57/BL mice.

The multiplication of 8 strains of herpes simplex virus of type 1 and 2 in normal and stimulated macrophages of NMRI and C57/bl mice was tested. Only 3 strains multiplied in normal NMRI macrophages, whereas all strains multiplied in stimulated cells. No multiplication except of one strain was observed in C57/bl macrophages. The multiplication rates of the virus strains correlated well with the determination of the acid-soluble and acid-insoluble thymidine (dTR) radioactivity and autoradiographic studies of infected (normal and stimulated) NMRI and C57/bl macrophages. The influence of the age of mice used for obtaining the macrophages was also studied. In stimulated macrophages more viral DNA was synthesised than in non-stimulated cells.