Heterologous expression of Alteromonas macleodii and Thiocapsa roseopersicina [NiFe] hydrogenases in Escherichia coli.

HynSL from Alteromonas macleodii 'deep ecotype' (AltDE) is an oxygen-tolerant and thermostable [NiFe] hydrogenase. Its two structural genes (hynSL), encoding small and large hydrogenase subunits, are surrounded by eight genes (hynD, hupH and hypCABDFE) predicted to encode accessory proteins involved in maturation of the hydrogenase. A 13 kb fragment containing the ten structural and accessory genes along with three additional adjacent genes (orf2, cyt and orf1) was cloned into an IPTG-inducible expression vector and transferred into an Escherichia coli mutant strain lacking its native hydrogenases. Upon induction, HynSL from AltDE was expressed in E. coli and was active, as determined by an in vitro hydrogen evolution assay. Subsequent genetic analysis revealed that orf2, cyt, orf1 and hupH are not essential for assembling an active hydrogenase. However, hupH and orf2 can enhance the activity of the heterologously expressed hydrogenase. We used this genetic system to compare maturation mechanisms between AltDE HynSL and its Thiocapsa roseopersicina homologue. When the structural genes for the T. roseopersicina hydrogenase, hynSL, were expressed along with known T. roseopersicina accessory genes (hynD, hupK, hypC1C2 and hypDEF), no active hydrogenase was produced. Further, co-expression of AltDE accessory genes hypA and hypB with the entire set of the T. roseopersicina genes did not produce an active hydrogenase. However, co-expression of all AltDE accessory genes with the T. roseopersicina structural genes generated an active T. roseopersicina hydrogenase. This result demonstrates that the accessory genes from AltDE can complement their counterparts from T. roseopersicina and that the two hydrogenases share similar maturation mechanisms.

Requirement of the DEAD-Box protein ded1p for messenger RNA translation.

The DED1 gene, which encodes a putative RNA helicase, has been implicated in nuclear pre-messenger RNA splicing in the yeast Saccharomyces cerevisiae. It is shown here by genetic and biochemical analysis that translation, rather than splicing, is severely impaired in two newly isolated ded1 conditional mutants. Preliminary evidence suggests that the protein Ded1p may be required for the initiation step of translation, as is the distinct DEAD-box protein, eukaryotic initiation factor 4A (eIF4A). The DED1 gene could be functionally replaced by a mouse homolog, PL10, which suggests that the function of Ded1p in translation is evolutionarily conserved.

Isolation and characterization of nuclear RNA polymerase II from chicken myeloblastosis cells.

Nuclear RNA polymerases of chicken myeloblastosis cells were solubilized and fractionated by diethylaminoethyl-Sephades A25 column chromatography. Both alpha-amanitin-insenstitive (polymerase I) and- sensitive (polymerase II) species were isolated. Polymerase activity, contained two peaks of enzyme (IIa and IIb), which were further purified by glycerol gradient centrifugation. The partially purified enzymes were characterized by their requirement of four nucleoside triphosphates and metal ions and by their sensitivity to several inhibitors. The enzymes were compared with RNA polymearases derived from normal chickent bone marrow cells,and the total extractable myeloblastosis than in bone marrow cells. Polymearse II from both cell types was shown to be sensitive to cytosine arabinoside triphosphate inhibiton.

Interaction of three second-generation anthracyclines with polynucleotides, RNA, DNA, and nucleosomes.

The interaction of three second-generation anthracycline derivatives with polynucleotides, supercoiled DNA, and calf thymus nucleosomes has been studied by terbium fluorescence measurements and agarose gel electrophoresis. It was shown that, as expected, N-trifluoroacetyladriamycin-14-valerate had little detectable effect on the fluorescence of this guanine-specific probe except for polydisperse calf thymus linear DNA fragments. The soluble analogue, N-trifluoroacetyladriamycin-14-O-hemiadipate, did show marked effects on terbium fluorescence with all nucleic acids and nucleosomes, but the effects were generally not as striking as were those observed with the epimer, 4'-epi-Adriamycin, which tended to produce a similar effect to its parent drug, Adriamycin, showing that a marked change in the hexose ring did not appreciably affect the interaction of the drug with DNA. Changes in the electrophoretic mobility of supercoiled pBR322 DNA were observed only at very high drug concentrations, much higher than those required with Adriamycin or actinomycin D. The effect was a smearing of the form I DNA and the production of some circular relaxed form II DNA. The drugs produced the effect in the following order: Adriamycin greater than N-trifluoroacetyladriamycin-14-O-hemiadipate greater than or equal to epi-Adriamycin. N-Trifluoroacetyladriamycin-14-valerate had little effect, even at very high drug concentrations (1:2, drug:DNA ratios).

Nucleoside uptake and membrane fluidity studies on N-trifluoroacetyladriamycin-14-O-hemiadipate-treated human leukemia and lymphoma cells.

N-Trifluoroacetyladriamycin-14-O-hemiadipate (AD 143), a DNA nonbinding derivative of Adriamycin, was studied for its effect on the uptake of labeled nucleosides into human leukemia (ML-1) and lymphoma (P3HR-1) cells in culture. After preincubation with AD 143 at concentrations as low as 5.2 microM (ML-1) or 13 microM (P3HR-1), the ability of the cells to take up extracellular labeled nucleosides was decreased by more than 50%. Similar experiments with Escherichia coli cells showed that AD 143 at the same concentrations did not have any effect. Influx of [3H]thymidine or [3H]uridine was studied by centrifugation of the cells through phthalate oil mixture, and it was found that the influx of the labeled nucleosides was decreased after treatment of the cells with AD 143. An increase in the membrane fluidity was observed after treatment of the cells with AD 143, as revealed by electron paramagnetic resonance spectroscopy studies. These observations suggest that the decreased incorporation of [3H]thymidine and [3H]uridine into acid-precipitable material that we observed earlier in the AD 143-treated cells may in part be the result of the AD 143-induced alteration of cell membrane activities, which in turn causes an inhibition of nucleoside uptake.

Inhibition of human lymphoma DNA-dependent RNA polymerase activity by 6-mercaptopurine ribonucleoside triphosphate.

6-Mercaptopurine was found to inhibit the growth of cultured human lymphoma P3HR-1 cells and the incorporation of [3H]-uridine into trichloroacetic acid-precipitable materials of the cells. One of the derivatives of 6-mercaptopurine, 6-mercaptopurine ribonucleoside triphosphate (6-thio-ITP), was found to inhibit in vitro RNA synthesis (both engaged and free enzyme activities) of the isolated nuclei from P3HR-1 cells. The alpha-amanitin-resistant RNA polymerase (polymerase I) and alpha-amanitin-sensitive RNA polymerase (polymerase II) of the cells were isolated and partially purified by either diethylaminoethyl cellulose or diethylaminoethyl Sephadex column chromatography, followed by DNA-cellulose affinity chromatography. It was found that these partially purified enzymes were also sensitive to 6-thio-ITP inhibition. Kinetic studies showed that the inhibition of RNA polymerase activities by 6-thio-ITP could be reversed by increasing concentrations of guanosine 5'-triphosphate in the reaction mixture, indicating that 6-thio-ITP may act as a competitive inhibitor of the enzymes by competing with guanosine 5'-triphosphate for its enzyme-binding site. These data suggest that inhibition of RNA transcription by 6-thio-ITP may be considered as one of the mechanisms of the cytotoxic action of 6-mercaptopurine in human tumor cells.

Effects of nitrosoureas on human DNA polymerase activities from acute and chronic granulocytic leukemia cells.

In vitro DNA synthesis by isolated cytoplasmic DNA polymerases of human leukemic cells was found to be inhibited by 1,3-bis(2-chloroethyl)-1-nitrosourea, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea and 1-(2-chloroethyl)-3-(trans-4-methyl-cyclohexyl)-1-nitrosourea. 2-Chloroethyl isocyanate and cyclohexyl isocyanate, the decomposition products of 1,3-bis(2-chloroethyl)-1-nitrosourea and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, respectively, are as effective as their parent nitrosoureas in inhibiting the enzyme activity. Preincubation studies indicated that these compounds inhibit DNA synthesis primarily by altering the enzyme DNA polymerases without significantly affecting the DNA template activities.

Isolation and purification of protein kinase C from human leukemia ML-1 cells phosphorylation of human leukemia RNA polymerase II in vitro.

Protein kinase C (PKC) was purified to near homogeneity from human leukemia ML-1 cells. The purified enzyme showed a single polypeptide band of 80 kDa on SDS-polyacrylamide gel after electrophoresis, and was totally dependent on Ca2+/phospholipid for activity. Diacylglycerol and the tumor-promoting on Ca2/phospholipid for activity. Diacylglycerol and the tumor-promoting phorbol esters stimulated the enzyme activity. Autophosphorylation of PKC purified from phenyl-Sepharose column showed both 80- and 37 kDa polypeptides. Further fractionation of PKC on a hydroxyapatite column revealed two peaks of enzyme activity, indicating that there may be two different forms of protein kinase C present in human leukemia cells. The purified PKC was used to phosphorylate RNA polymerase II of human leukemia cells in vitro and the autoradiogram showed that RNA polymerase II large subunits (240, 220 and 150 kDa) were phosphorylated in a time-dependent manner.

Inhibition of the replication of native and 3'-azido-2',3'-dideoxythymidine (AZT)-resistant simian immunodeficiency virus (SIV) by 3-nitrosobenzamide.

The 3-nitrosobenzamide (NOBA) drug abolishes SIV replication sharply at 20 microM concentration when CEM x 174 cells are preincubated for 1 h with the drug prior to viral infection. Treatment of CEM x 174 cells with 20 microM NOBA resulted in the inhibition of the synthesis of the DNA sequence coding for the gag gene, as determined by the PCR technique. Cell viability was directly proportional to the antiviral action of NOBA. Replication of AZT-resistant SIV 23740 in MMU 23740 cells in vitro was suppressed by NOBA in a concentration-dependent manner without significant effects on cell viability. Reverse transcriptase activity of SIVmac239 was unaffected by NOBA up to 800 microM concentration. Preincubation of two SIV strains with NOBA completely abolished their infectivity in human PHA-PBL cells. Replication of two strains of SIV in PHA-PBL cells was also inhibited by NOBA.

The 24,000 Da subunit is not required for the RNA synthesis activity of chicken leukemia RNA polymerase II.

The partially purified RNA polymerase II from chicken leukemia cells (Chuang R. Y., Chuang L. F. & Israel M. (1986) Biochem. Pharmacol. 35, 1293-1297) contained multiple subunits with molecular masses (in Da) ranging from 220,000 to 24,000, as shown by SDS-polyacrylamide gel electrophoresis. The enzyme was further purified through phosphocellulose column and fractions containing the enzyme activity were collected and concentrated 400-fold through a microconcentrator. The microconcentrator contained a membrane with a molecular weight cutoff around 30,000 and, hence, removed the 24,000 Da polypeptide from the enzyme. It was found that the resulting enzyme retained all the catalytic activity as compared to the enzyme preparation before the concentration step, suggesting that the stoichiometric amount of the 24,000 Da polypeptide is not required for RNA synthesis activity with a denatured DNA template.

The spliced leader gene of Angiostrongylus cantonensis.

A 5' leader sequence has been identified on mRNAs of the parasitic nematode Angiostrongylus cantonensis. A 720-bp XhoI restriction fragment containing the gene encoding the leader sequence has been cloned and sequenced. It contains a 22-nt sequence identical to that of the leader sequence of Caenorhabditis elegans, a consensus splice site and a putative Sm antigen binding site. The gene is present as a tandem repeating unit of approximately 60 copies, and unlike C. elegans it is not associated with the 5S ribosomal RNA gene. The SL-RNA is 110 nt long and the sequence and primer extension studies suggest that it is transcribed from the tandemly repeating SL gene. It is precipitable from cell-free extracts of adult nematodes by anti-Sm anti-sera, and from RNA by anti-TMG anti-sera, thus suggesting its inclusion with small nuclear ribonucleoproteins in RNA splicing.

Interaction of N-trifluoroacetyladriamycin-14-O-hemiadipate with chicken leukemia RNA polymerase. Formation of drug-enzyme complex.

The biochemical mechanism of the N-trifluoroacetyladriamycin-14-O-hemiadipate-induced inhibition of RNA synthesis in vitro by chicken (myeloblastosis) leukemia RNA polymerase II was studied. The inhibition was found to be dependent upon preincubation of the drug with the enzyme prior to enzyme assays, suggesting that drug-enzyme interactions occur. A drug-enzyme association complex was subsequently isolated through glycerol gradient sedimentation and further characterized by fluorescent microscopic studies. The drug was dissociated from the complex upon sodium dodecyl sulfate (SDS)-gel electrophoresis, revealing the non-covalent nature of the binding between the drug and the RNA polymerase.

Activation of human leukemia protein kinase C by tumor promoters and its inhibition by N-trifluoroacetyladriamycin-14-valerate (AD 32).

N-Trifluoroacetyladriamycin-14-valerate (AD 32), a lipophilic, DNA non-binding analog of Adriamycin (ADR), was found to be a potent inhibitor of the membrane-bound enzyme, protein kinase C (PKC). PKC was isolated and purified from human leukemia ML-1 cells, and the enzyme activity was shown to be activated by the tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA) and phorbol-12,13-dibutyrate (PDBu). AD 32, nevertheless, inhibited the activation of PKC by TPA or PDBu. The IC50 values for AD 32 inhibition of PKC activation were 0.85 microM for TPA and 1.25 microM for PDBu. Under the same assay conditions, ADR demonstrated much higher IC50 values: 550 microM for TPA and greater than 350 microM for PDBu. The inhibition of PKC by AD 32 was further shown to be competitive in nature; AD 32 inhibited the binding of [3H]PDBu to PKC. Therefore, AD 32 competes with the tumor promoter for the PKC binding site and prevents the latter from both interacting with the phospholipid and binding to PKC. These effects of AD 32 were reproduced in situ; incubation of human leukemia ML-1 cells with TPA showed an increased phosphorylation of cellular proteins, and the TPA-induced protein phosphorylation was inhibited by the addition of AD 32 to the cultured cells.

A simple method to distinguish between simian immunodeficiency virus isolates by restriction analysis of PCR products.

A simple method to distinguish between simian immunodeficiency virus (SIV) isolates of experimentally infected rhesus macaques is reported. Peripheral blood mononuclear cells (PBMC) were prepared from a rhesus macaque infected with SIVStM isolated originally from a stump-tailed macaque, or from a rhesus monkey infected with SIVSM from a sooty mangabey monkey. PBMC were cocultivated with CEM x 174 cells and a region of the SIV envelope (env) gene was amplified by the polymerase chain reaction (PCR) from cDNA of infected cocultivation cells. Restriction enzyme digestion analysis of the PCR products enabled SIVStM and SIVSM to be differentiated from each other, and from a molecular clone of SIVMAC, SIVMAC239, originally isolated from an infected rhesus macaque. Furthermore, when SIVSM and SIVStM were introduced into the same animal, restriction enzyme analysis of the PCR product amplified from cocultivation cells of this rhesus macaque suggested that the animal was superinfected.

Detecting bluetongue virus RNA in cell culture by dot hybridization with a cloned genetic probe.

A 70% copy of genome segment 7 of bluetongue virus (BTV)-17 has been cloned into the plasmid pBR-322. This cloned BTV segment when used as a radioactive probe will hybridize to BTV double-stranded RNA extracted from cell cultures and dotted onto nitrocellulose paper. This dot hybridization technique is therefore suitable for detecting and identifying BTV in cell culture. The specificity of cloned probes is discussed in relation to detecting gene sequences specific for either the bluetongue serogroup or different serotypes of BTV.

Colony hybridizations using nylon membranes and RNA probes--an improved method for screening bacterial clones containing bluetongue virus genome.

Bluetongue virus (BTV) total genomic and isolated individual segment dsRNAs end-labeled with 32P were successfully used as probes in colony hybridization to detect clones of BTV genomic material. The RNA probes were highly specific for cloned BTV genomic material. DNA probes, however, gave false positive results. DNA from bacterial clones was fixed to nylon and nitrocellulose membranes. The hybridized nylon membranes could be stripped of probe and reprobed at least 6 times without loss of signal strength.

Comparison of dot-blot and Northern blot hybridizations in the determination of genetic relatedness of United States bluetongue virus serotypes.

Dot-blot and Northern blot hybridization methods to determine the genetic relatedness of United States bluetongue virus serotypes 2, 10, 11, 13, and 17 were compared. Both plasmid and insert DNA probes from cloned BTV-17 dsRNA segments 2, 5, 6, and 8 were hybridized to dsRNA from the BTV serotypes and epizootic hemorrhagic disease virus (EHDV). Stringencies of hybridization were kept identical, and experiments differed only in the method in which dsRNA was applied to the membranes (dot-blot or Northern blot). The Northern blot hybridization method yielded more consistent results, and it was visually and unequivocally shown to which dsRNA segment a cDNA probe bound, since the dsRNA segments were separated by PAGE prior to blotting and hybridization. In contrast, the dot-blot hybridization method gave less consistent results. Identical results for plasmid and insert probes were obtained for Northern blot hybridizations but not for dot-blot hybridizations. At least two probes could be used simultaneously in Northern blot hybridizations.

Detection of simian immunodeficiency virus RNA from infected rhesus macaques by the polymerase chain reaction.

A rapid method for the detection of simian immunodeficiency virus (SIV) RNA from peripheral blood mononuclear cells (PBMC) of experimentally infected rhesus macaques by the polymerase chain reaction (PCR) is reported. The PCR was carried out with a complementary DNA (cDNA) template using 3 pairs of primers that were designed to anneal to homologous sequences in conserved regions of 3 molecular clones of SIVmac. The specificity of the primers was confirmed by performing the PCR with template DNA from the 3 molecular clones. SIV-specific RNA was detected from 30 and 50 infected PBMC/6.25 x 10(5) PBMC of two animals.

Kappa-opioid receptors on lymphocytes of a human lymphocytic cell line: morphine-induced up-regulation as evidenced by competitive RT-PCR and indirect immunofluorescence.

We have previously shown that classical brain-like kappa opioid receptors (KOR) are constitutively expressed in lymphocytic cells. including human CEM x174 T-B hybrid cells, Jurkat -T4 cells, human peripheral blood mononuclear cells (PBMC), human CD4+ cells and monkey PBMC (Biochem. Biophys. Res. Commun. 209 (1995) 1003). The present study further demonstrates that the KOR of lymphocytes are activated in the presence of extracellular morphine or U50,488H, a KOR selective agonist, and the activation causes an increase in the expression of KOR mRNA, as determined by a quantitative competitive Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) procedure. The observed agonist-induced KOR up-regulation was blocked by treating the cells with either naloxone (a KOR-partially selective antagonist) or nor-binaltorphimine (a KOR-selective antagonist). Up-regulation of lymphocytic KOR by morphine was also evidenced by flow cytometric analysis of phycoerythrin (PE) amplification of fluorescein isothiocyanate-conjugated arylacetamide labeling of the KOR. Although morphine binds primarily to mu-opioid receptors, together with the previously reported phenomenon that morphine modulation of immune functions also exists in mu-opioid receptor knockout mice, the present study confirms that opioids such as morphine may exert their effects through multiple opioid receptor types and that the effects of morphine or endogenous opioids on immune cells could not be simply adduced from the anticipated effects of a synthetic, selective opioid receptor ligand.

The effect of the insecticide heptachlor on ras proto-oncogene expression in human myeloblastic leukemia (ML-1) cells.

Expression of the ras proto-oncogene mRNA in human myeloblastic leukemia (ML-1) cells was analyzed as a function of cDNA amplification by polymerase chain reaction (PCR). By using a pair of oligonucleotides that flank exon-2 from opposite strands (5' and 3') of H-ras cDNA for PCR amplification, ML-1 cells were found to express a 112 bp segment of the ras transcript. A rapid decline in the expression of this transcript was seen in cells treated with heptachlor, a chlorinated hydrocarbon insecticide. Expression of the same ras segment was not affected by treatment of ML-1 with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Furthermore, addition of serum to quiescent, heptachlor-treated cultures of ML-1 cells inhibited the effect of heptachlor and restored the expression of the ras protooncogene mRNA.