Equivalent inhibition of half-site and full-site retroviral strand transfer reactions by structurally diverse compounds.

In vitro assay systems which use recombinant retroviral integrase (IN) and short DNA oligonucleotides fail to recapitulate the full-site integration reaction as it is known to occur in vivo. The relevance of using such circumscribed in vitro assays to define inhibitors of retroviral integration has not been formerly demonstrated. Therefore, we analyzed a series of structurally diverse inhibitors with respect to inhibition of both half-site and full-site strand transfer reactions with either recombinant or virion-produced IN. Half-site and full-site reactions catalyzed by avian myeloblastosis virus and human immunodeficiency virus type 1 (HIV-1) IN from virions are shown to be equivalently sensitive to inhibition by compounds which inhibit half-site reactions catalyzed by the recombinant HIV-1 IN. These studies therefore support the utility of using in vitro assays employing either recombinant or virion-derived IN to identify inhibitors of integration.     

Expression cloning of oncogenes by retroviral transfer of cDNA libraries.

a cDNA library transfer system based on retroviral vectors has been developed for expression cloning in mammalian cells. The use of retroviral vectors results in stable cDNA transfer efficiencies which are at least 100-fold higher than those achieved by transfection and therefore enables the transfer and functional screening of very large libraries. In our initial application of retroviral transfer of cDNA libraries, we have selected for cDNAs which induce oncogenic transformation of NIH 3T3 fibroblasts, as measured by loss of contact inhibition of proliferation. Nineteen different transforming cDNAs were isolated from a total of 300,000 transferred cDNA clones. Three of these cDNAs were derived from known oncogenes (raf-1, lck, and ect2), while nine others were derived from genes which had been cloned previously but were not known to have the ability to transform fibroblasts (beta-catenin, thrombin receptor, phospholipase C-gamma 2 and Spi-2 protease inhibitor genes). The Spi-2 cDNA was expressed in antisense orientation and therefore is likely to act as an inhibitor of an endogenous transformation suppressor. Seven novel cDNAs with transforming activities, including those for three new members of the CDC24 family of guanine nucleotide exchange factors, were also cloned from the retroviral cDNA libraries. Retroviral transfer of libraries should be generally useful for cloning cDNAs which confer selectable phenotypes on many different types of mammalian cells.     

Design,synthesis and evaluation of structurally diverse chrysin-chromene-spirooxindole hybrids as anticancer agents

A series of structurally diverse chrysin-chromene-spirooxindole hybrids were designed, synthesized via a Knoevenagel/Michael/cyclization of chrysin and isatylidene malononitrile derivatives through utilizing a hybrid pharmacophore approach. The newly synthesized compounds were evaluated for their in vitro anticancer activity, and most of the compounds showed stronger anti-proliferative activity than parent compound chrysin. In particular, compound 3e had the highest cytotoxicity towards A549 cells (IC₅₀ = 3.15 ± 0.51 μM), and had better selectivity in A549 cells and normal MRC-5 cells. Furthermore, compound 3e could significantly inhibit the proliferation and migration of A549 cells in a dose-dependent manner, as well as induce the apoptosis possibly through mitochondria-mediated caspase-3/8/9 activation and multi-target co-regulation of the p53 signaling pathway. Thus, our results provide in vitro evidence that compound 3e may be a potential candidate for the development of new anti-tumour drugs.     

Utilisation of structurally diverse organophosphonates by Streptomycetes

A group of streptomycete strains was found able to utilise a wide range of structurally diverse phosphonates as a sole phosphorus source. No relation could be observed between ability to synthesise compounds containing a direct carbon-to-phosphorus (C-P) bond and biodegradative potential towards phosphonates in the strains studied. Streptomyces morookaensis DSM 40565 could degrade 2-amino-4-phosphonobutyrate as a sole nitrogen and phosphorus source in a stereoselective-like manner. This result suggests the existence of a new metabolic pathway for C-P bond breakage.     

One- and two-step transformations of rat thyroid epithelial cells by retroviral oncogenes.

A system of epithelial cells is described in which it is possible to study the number and the nature of genes capable of conferring the malignant phenotype. Two fully differentiated, hormone-responsive cell lines from rat thyroid glands are presented which are susceptible to one-step or two-step transformation upon infection with several murine acute retroviruses. After infection, both cell lines became independent from their thyrotropic hormone requirement for growth. However, complete transformation was achieved with one of the cell lines (FRTL-5 Cl 2), whereas the other cell line (PC Cl 3) failed to grow in agar and to give rise to tumors in vivo. The latter cell line was susceptible to complete transformation upon cooperation of the v-ras-Ha and the human c-myc oncogenes.     

Deacylation of structurally diverse lipopolysaccharides by human acyloxyacyl hydrolase

Acyloxyacyl hydrolase, a leukocyte enzyme previously has been shown to catalyze the hydrolysis of secondary (acyloxyacyl-linked) fatty acyl chains from the nonreducing glucosamine of the lipid A region of rough Salmonella typhimurium lipopolysaccharide (LPS). We describe here the activity of this enzyme toward smooth S. typhimurium LPS and LPS from Escherichia coli, Pseudomonas aeruginosa, Haemophilus influenzae, Neisseria meningitidis, and Neisseria gonorrhoeae. Acyloxyacyl hydrolase released the secondary acyl chains from all of these lipopolysaccharides, regardless of the location of the acyloxyacyl linkage on the diglucosamine backbone or the structure of the acyl chains. The two acyloxyacyl linkages present in each LPS molecule apparently were hydrolyzed separately, so that free fatty acids released from the different sites accumulated at different rates. The purified enzyme also removed greater than 90% of the secondary acyl chains in each LPS, indicating that the enzyme acts not only on intact LPS but also on LPS molecules that have only one secondary acyl chain. The enzyme did not release the glucosamine-linked 3-hydroxyacyl chains. The specificity and versatility of the enzyme for cleaving acyloxyacyl linkages suggest that it may be a useful reagent for studying the structure and bioactivities of lipopolysaccharides with diverse carbohydrate and lipid A structures.     

Dissimilarity-based algorithms for selecting structurally diverse sets of compounds.

This paper commences with a brief introduction to modern techniques for the computational analysis of molecular diversity and the design of combinatorial libraries. It then reviews dissimilarity-based algorithms for the selection of structurally diverse sets of compounds in chemical databases. Procedures are described for selecting a diverse subset of an entire database, and for selecting diverse combinatorial libraries using both reagent-based and product-based selection.     

Piroxicam, a structurally novel anti-inflammatory compound. Mode of prostaglandin synthesis inhibition

Piroxicam is a potent inhibitor of prostaglandin biosynthesis. Experiments utilizing cell culture and microsomes derived from various sources have demonstrated that piroxicam is a selective inhibitor of the cyclooxygenase step of arachidonic acid metabolism. Little blocking activity is observed at the phospholipase, thromboxane or prostacyclin synthetase, and arachidonic acid lipoxygenase steps.     

Piroxicam, a structurally novel anti-inflammatory compound. Mode of prostaglandin synthesis inhibition

Piroxicam is a potent inhibitor of prostaglandin biosynthesis. Experiments utilizing cell culture and microsomes derived from various sources have demonstrated that piroxicam is a selective inhibitor of the cyclooxygenase step of arachidonic acid metabolism. Little blocking activity is observed at the phospholipase, thromboxane or prostacyclin synthetase, and arachidonic acid lipoxygenase steps.     

A common denominator linking glycogen metabolism, nuclear oncogenes and development.

A ubiquitous protein-serine kinase, initially implicated in glycogen regulation, has surfaced unexpectedly in the fields of nuclear oncogenes and fruitfly development. This unusual linkage may reflect the role of this kinase in phosphorylating proteins normally activated by dephosphorylation, thus providing a priming function. Loss of such a primer would result in constitutive activation of substrates, a scenario concordant with the dramatic and pleiotropic phenotype observed in Drosophila null mutants.     

Hypopigmentation: a common feature of Prader-Labhart-Willi syndrome.

In order to determine the frequency and characterization of hypopigmentation in Prader-Labhart-Willi syndrome (PLWS), clinical, cytogenetic and biochemical findings are reported in 56 PLWS individuals. Forty-eight percent of the individuals with PLWS met the criteria for hypopigmentation. Hypopigmentation in PLWS individuals appears to be as common as previously recognized features such as behavioral problems and dental abnormalities. Significant differences in hair color, sun sensitivity, and complexion were found between those PLWS patients with the chromosome 15 deletion and those with normal chromosomes. Individuals with the deletion frequently had lighter hair color, more sun sensitivity, and fairer complexion than did either other family members or nondeletion PLWS patients. No significant differences in biochemical findings (phenylalanine, tyrosine, catecholamines, or beta-melanocyte-stimulating hormone) were found between deletion and nondeletion PLWS patients or between hypopigmented and normally pigmented patients. The data suggest that a gene(s) controlling the activity of tyrosinase or other enzymes required for melanin production is located on proximal 15q.     

Inhibition of diverse opportunistic viruses by structurally optimized retrograde trafficking inhibitors

Opportunistic viruses are a major problem for immunosuppressed individuals, particularly following organ or stem cell transplantation. Current treatments are non-existent or suffer from problems such as high toxicity or development of resistant strains. We previously published that a trafficking inhibitor that targets a host protein greatly reduces the replication of human cytomegalovirus. This inhibitor was also shown to be moderately effective against polyomaviruses, another family of opportunistic viruses. We have developed a panel of analogues for this inhibitor and have shown that these analogues maintain their high efficacy against HCMV, while substantially lowering the concentration required to inhibit polyomavirus replication. By targeting a host protein these compounds are able to inhibit the replication of two very different viruses. These observations open up the possibility of pan-viral inhibitors for immunosuppressed individuals that are effective against multiple, diverse opportunistic viruses.     

A general synthesis of structurally diverse building blocks for preparing analogues of C-linked antifreeze glycoproteins

A synthetic methodology to afford unusual glycoconjugate building blocks useful for the solid-phase synthesis of C-linked antifreeze glycoprotein (AFGP) analogues is described. Such compounds are urgently required in order to elucidate the molecular mechanism by which AFGPs function. All reactions are general in nature and accommodate structural variation in the carbohydrate moiety, polypeptide backbone, and amino acid side chain.     

Solid-phase synthesis of structurally diverse scaffolded peptides for the mimicry of discontinuous protein binding sites

Scaffolded peptides, in which fragments of the sequence are presented through a molecular scaffold in a discontinuous and nonlinear fashion, are promising candidates for the mimicry of discontinuous protein binding sites. Twelve scaffold molecules based on cyclic peptides with ring sizes ranging from 13 to 30 were generated. Up to three different peptide fragments were attached to the scaffolds in a site-selective manner, yielding scaffolded peptides in excellent purities, as documented by MS, HPLC, and 2D (1)H NMR spectroscopy data.     

Differential inductions of TNF-alpha and IGTP, IIGP by structurally diverse classic and non-classic lipopolysaccharides

The innate immune system recognizes microbes by characteristic molecules like the Gram-negative lipopolysaccharide (LPS). Lipid A (the LPS bioactive moiety) signals through toll-like receptors (TLRs) to induce pro-inflammatory molecules and small GTPases of the p47 family involved in intracellular pathogen control. We tested TNF-alpha and p47-GTPase induction in macrophages using classical LPSs [lipid As with glucosamine backbones, ester- and amide-linked C14:0(3-OH) and C12 to C16 in acyloxyacyl groups] of wild type and mutant Escherichia coli and Yersinia species and non-classical LPSs [lipid As with diaminoglucose, ester-linked 3-OH-fatty acids and C28:0(27-OH) and C23:0(29-OH) in acyloxyacyl groups] of plant endosymbionts (Rhizobium), intracellular pathogens (Brucella and Legionella) and phylogenetically related opportunistic bacteria (Ochrobactrum). Classical but not non-classical LPSs efficiently induced TNF-alpha, IIGP and IGTP p47-GTPase expression. Remarkably, the acyloxyacyl groups in classical LPSs necessary to efficiently induce TNF-alpha were not necessary to induce p47-GTPases, suggesting that different aspects of lipid A are involved in this differential induction. This was confirmed by using PPDM2, a non-endotoxic lipid A-structurally related synthetic glycolipid. Despite their different bioactivity, all types of LPSs signalled through TLR-4 and not through TLR-2. However, whereas TNF-alpha induction was myeloid differentiation factor 88 (MyD88)-dependent, that of p47-GTPases occurred via a MyD88-independent pathway. These observations show that different aspects of the LPS pathogen-associated molecular pattern may be triggering different signalling pathways linked to the same TLR. They also reinforce the hypothesis that non-classical lipid As act as virulence factors by favouring the escape from the innate immune system.     

Suppression of retroviral MA deletions by the amino-terminal membrane-binding domain of p60src.

The molecular mechanism by which retroviral Gag proteins are directed to the plasma membrane for the formation of particles (budding) is unknown, but it is widely believed that the MA domain, located at the amino terminus, plays a critical role. Consistent with this idea, we found that small deletions in this segment of the Rous sarcoma virus Gag protein completely blocked particle formation. The mutant proteins appear to have suffered only localized structural damage since they could be rescued (i.e., packaged into particles) when coexpressed with Gag proteins that are competent for particle formation. To our surprise, the effects of the MA deletions could be completely suppressed by fusing as few as seven residues of the myristylated amino terminus of the oncoprotein p60src to the beginning of the mutant Gag proteins. Particles produced by the chimeras were of the same density as the wild type. Two myristylated peptides having sequences distinct from that of p60src were entirely unable to suppress MA deletions, indicating that myristate alone is not a sufficient membrane targeting signal. We hypothesize that the amino terminus of p60src suppresses the effects of MA deletions by diverting the Rous sarcoma virus Gag protein from its normal site of assembly to the Src receptor for particle formation.     

P450 gene induction by structurally diverse xenochemicals: central role of nuclear receptors CAR, PXR, and PPAR.

The biochemistry of foreign compound metabolism and the roles played by individual cytochrome P450 (CYP) enzymes in drug metabolism and in the toxification and detoxification of xenochemicals prevalent in the environment are important areas of molecular pharmacology and toxicology that have been widely studied over the past decade. Important advances in our understanding of the mechanisms through which foreign chemicals impact on these P450-dependent metabolic processes have been made during the past 2 years with several key discoveries relating to the mechanisms through which xenochemicals induce the expression of hepatic P450 enzymes. Roles for three "orphan" nuclear receptor superfamily members, designated CAR, PXR, and PPAR, in respectively mediating the induction of hepatic P450s belonging to families CYP2, CYP3, and CYP4 in response to the prototypical inducers phenobarbital (CAR), pregnenolone 16alpha-carbonitrile and rifampicin (PXR), and clofibric acid (PPAR) have now been established. Two other nuclear receptors, designated LXR and FXR, which are respectively activated by oxysterols and bile acids, also play a role in liver P450 expression, in this case regulation of P450 cholesterol 7alpha-hydroxylase, a key enzyme of bile acid biosynthesis. All five P450-regulatory nuclear receptors belong to the same nuclear receptor gene family (family NR1), share a common heterodimerization partner, retinoid X-receptor (RXR), and are subject to cross-talk interactions with other nuclear receptors and with a broad range of other intracellular signaling pathways, including those activated by certain cytokines and growth factors. Endogenous ligands of each of those nuclear receptors have been identified and physiological receptor functions are emerging, leading to the proposal that these receptors may primarily serve to modulate hepatic P450 activity in response to endogenous dietary or hormonal stimuli. Accordingly, P450 induction by xenobiotics may in some cases lead to a perturbation of endogenous regulatory circuits with associated pathophysiological consequences.     

Increased intracellular glycerophosphoinositol is a biochemical marker for transformation by membrane-associated and cytoplasmic oncogenes

Transformation of rodent fibroblasts by cytoplasmic (mos, raf) and membrane-associated (ras, src, met, trk), but not nuclear (myc, fos) oncogenes results specifically in a very significant elevation of intracellular levels of glycerophosphoinositol (GPI). This elevation is specifically associated with the transformed state of the cells and not merely with their active state of proliferation. The basal phospholipase A2 (PLA2) activity of the same cells is also significantly stimulated in vivo. Our results are consistent with the notion that the elevated levels of GPI result from deacylation of lysophosphatidylinositol released by the enhanced PLA2 activity. GPI is a water-soluble, easily detectable metabolite which may constitute a convenient biochemical marker for malignant transformation by this particular group of oncogenes.