Establishment of a Dual-Vector System for Gene Delivery Utilizing Prototype Foamy Virus

Foamy viruses (FVs) are generally recognized as non-pathogenic, often causing asymptomatic or mild symptoms in infections. Leveraging these unique characteristics, FV vectors hold significant promise for applications in gene therapy. This study introduces a novel platform technology using a pseudo-virus with single-round infectivity. In contrast to previous vector approaches, we developed a technique employing only two vectors, pcHFV lacking Env and pCMV-Env, to introduce the desired genes into target cells. Our investigation demonstrated the efficacy of the prototype foamy virus (PFV) dual-vector system in producing viruses and delivering transgenes into host cells. To optimize viral production, we incorporated the codon-optimized Env (optEnv) gene in pCMV-Env and the Woodchuck Hepatitis Virus Posttranscriptional Regulatory Element (WPRE) at the 3' end of the transgene in the transfer vector. Consequently, the use of optEnv led to a significant enhancement in transgene expression in host cells. Additionally, the WPRE exhibited an enhancing effect. Furthermore, the introduced EGFP transgene was present in host cells for a month. In an effort to expand transgene capacity, we further streamlined the viral vector, anticipating the delivery of approximately 4.3 kbp of genes through our PFV dual-vector system. This study underscores the potential of PFVs as an alternative to lentiviruses or other retroviruses in the realm of gene therapy.

Foamy Virus Integrase in Development of Viral Vector for Gene Therapy

Due to the broad host suitability of viral vectors and their high gene delivery capacity, many researchers are focusing on viral vector-mediated gene therapy. Among the retroviruses, foamy viruses have been considered potential gene therapy vectors because of their non-pathogenicity. To date, the prototype foamy virus is the only retrovirus that has a high-resolution structure of intasomes, nucleoprotein complexes formed by integrase, and viral DNA. The integration of viral DNA into the host chromosome is an essential step for viral vector development. This process is mediated by virally encoded integrase, which catalyzes unique chemical reactions. Additionally, recent studies on foamy virus integrase elucidated the catalytic functions of its three distinct domains and their effect on viral pathogenicity. This review focuses on recent advancements in biochemical, structural, and functional studies of foamy virus integrase for gene therapy vector research.

IFITM proteins inhibit the late step of feline foamy virus replication

Interferon-induced transmembrane (IFITM) proteins as host restriction factors are known to inhibit the replication of several viruses. In this study, transient IFITM expression vectors were used to investigate whether IFITMs inhibit feline foamy viral (FFV) replication and which step of viral replication is inhibited. In our studies, viral production was significantly reduced when cells were infected with FFV at almost same times such as −3, 0, or 3 h post-transfection with IFITM vector. However viral production was not reduced even though cells were infected with FFV at 3 or 6 days post-transfection when production of IFITM proteins was maximized. Considering that IFITM expression was maximized at 3 days post-transfection, the stage of viral replication inhibited by IFITM appears to be the late step of viral replication. Moreover, the viral Gag proteins detected in the virus-infected cell lysates were proportionally correlated with viral titer of the culture supernatants. Therefore, it is likely that IFITMs can restrict production of FFV at the late step of viral replication.

Influence of Pretreatment with Immunosuppressive Drugs on Viral Proliferation

Immunosuppressive drugs are used to make the body less likely to reject transplanted organs or to treat autoimmune diseases. In this study, five immunosuppressive drugs including two glucocorticoids (dexamethasone and prednisolone), one calcineurin inhibitor (cyclosporin A), one non-steroid anti-inflammatory drug (aspirin), and one antimetabolite (methotrexate) were tested for their effects on viral proliferation using feline foamy virus (FFV). The five drugs had different cytotoxic effects on the Crandell-Ress feline kidney (CRFK) cells, the natural host cell of FFV. Dexamethasone-pretreated CRFK cells were susceptible to FFV infection, but pretreatment with prednisolone, cyclosporin A, aspirin, and methotrexate showed obvious inhibitory effects on FFV proliferation, by reducing viral production to 29.8-83.8% of that of an untreated control. These results were supported by western blot, which detected viral Gag structural protein in the infected cell lysate. As our results showed a correlation between immunosuppressive drugs and susceptibility to viral infections, it is proposed that immune-compromised individuals who are using immune-suppressive drugs may be especially vulnerable to viral infection originated from pets.

Single residue mutation in integrase catalytic core domain affects feline foamy viral DNA integration

DD(35)E motif in catalytic core domain (CCD) of integrase (IN) is extremely involved in retroviral integration step. Here, nine single residue mutants of feline foamy virus (FFV) IN were generated to study their effects on IN activities and on viral replication. As expected, mutations in the highly conserved D107, D164, and E200 residues abolished all IN catalytic activities (3'-end processing, strand transfer, and disintegration) as well as viral infectivity by blocking viral DNA integration into cellular DNA. However, Q165, Y191, and S195 mutants, which are located closely to DDE motif were observed to have diverse levels of enzymatic activities, compared to those of the wild type IN. Their mutant viruses produced by one-cycle transfection showed different infectivity on their natural host cells. Therefore, it is likely that effects of single residue mutation at DDE motif is critical on viral replication depending on the position of the residues.

Integrase C-terminal residues determine the efficiency of feline foamy viral DNA integration

Integrase (IN) is an essential enzyme in retroviral life cycle. It mediates viral cDNA integration into host cellular DNA. Feline foamy virus (FFV) is a member of the Spumavirus subfamily of Retroviridae. Recently, its life cycle has been proposed to be different from other retroviruses. Despite this important finding, FFV IN is not understood clearly. Here, we constructed point mutations in FFV IN C-terminal domain (CTD) to obtain a clear understanding of its integration mechanism. Mutation of the amino acid residues in FFV IN CTD interacting with target DNA reduced both IN enzymatic activities in vitro and viral productions in infected cells. Especially, the mutants, R307 and K340, made viral DNA integration less efficient and allowed accumulation of more unintegrated viral DNA, thereby suppressing viral replication. Therefore, we suggest that the CTD residues interacting with the target DNA play a significant role in viral DNA integration and replication.

Characterization of Prototype Foamy Virus Infectivity in Transportin 3 Knockdown Human 293t Cell Line

The foamy viruses are currently considered essential for development as vectors for gene delivery. Previous studies demonstrated that prototype foamy virus (PFV) can infect and replicate prevalently in a variety of cell types for its exclusive replication strategy. However, the virus-host interaction, especially PFV-transportin3 (TNPO3), is still poorly understood. In our investigation of the role of TNPO3 in PFV infection, we found lower virus production in TNPO3 knockdown (KD) cells compared with wild-type 293T cells. PCR analysis revealed that viral DNAs were mostly altered to circular forms: both 1-long terminal repeat (1-LTR) and 2-LTR in TNPO3 KD cells. We therefore suggest that TNPO3 is required for successful PFV replication, at least at/after the nuclear entry step of viral DNA. These findings highlight the obscure mysteries of PFV-host interaction and the requirement of TNPO3 for productive infection of PFV in 293T cells.

Distribution and fate of HIV-1 unintegrated DNA species: a comprehensive update

Reverse transcription of viral RNA and the subsequent integration of reverse transcripts are the classical early events of the HIV-1 life-cycle. Simultaneously, abundant unintegrated DNAs (uDNAs), are formed in cells ubiquitously. The uDNAs either undergo recombination or degradation or persist inactively for long periods in the nucleus as future resources. Among them, 2-LTR circles are considered a dead-end for viral spread. Their contribution to the HIV-1 infection is still poorly understood. Nevertheless, the preintegration transcription of the aberrant DNAs and the consequent alterations of cellular factors have already been reported. Since the major fate of the viral genome is to persist as episomal DNA, precise characterization is required for studying the biology of HIV-1. This review compiles the biochemical and genetic updates on uDNA in the HIV-1 life cycle and could provide direction to further study of their roles in HIV-1 replication and application in HIV-1 pathogenesis.

Cellular and viral determinants of retroviral nuclear entry

Retroviruses must integrate their cDNA into the host genome to generate proviruses. Viral DNA-protein complexes interact with cellular proteins and produce pre-integration complexes, which carry the viral genome and cross the nuclear pore channel to enter the nucleus and integrate viral DNA into host chromosomal DNA. If the reverse transcripts fail to integrate, linear or circular DNA species such as 1- and 2-long terminal repeats are generated. Such complexes encounter numerous cellular proteins in the cytoplasm, which restrict viral infection and protect the nucleus. To overcome host cell defenses, the pathogens have evolved several evasion strategies. Viral proteins often contain nuclear localization signals, allowing entry into the nucleus. Among more than 1000 proteins identified as required for HIV infection by RNA interference screening, karyopherins, cleavage and polyadenylation specific factor 6, and nucleoporins have been predominantly studied. This review discusses current opinions about the synergistic relationship between the viral and cellular factors involved in nuclear import, with focus on the unveiled mysteries of the host-pathogen interaction, and highlights novel approaches to pinpoint therapeutic targets.

Knockdown of the host cellular protein transportin 3 attenuates prototype foamy virus infection

Transportin 3 (TNPO3) is a member of the importin-ß superfamily proteins. Despite numerous studies, the exact molecular mechanism of TNPO3 in retroviral infection is still controversial. Here, we provide evidence for the role and mechanism of TNPO3 in the replication of prototype foamy virus (PFV). Our findings revealed that PFV infection was reduced 2-fold by knockdown (KD) of TNPO3. However, late stage of viral replication including transcription, translation, viral assembly, and release was not influenced. The differential cellular localization of PFV integrase (IN) in KD cells pinpointed a remarkable reduction of viral replication at the nuclear import step. We also found that TNPO3 interacted with PFV IN but not with Gag, suggesting that IN-TNPO3 interaction is important for nuclear import of PFV pre-integration complex. Our report enlightens the mechanism of PFV interaction with TNPO3 and support ongoing research on PFV as a promising safe vector for gene therapy.

Nuclear localization signals in prototype foamy viral integrase for successive infection and replication in dividing cells

We identified four basic amino acid residues as nuclear localization signals (NLS) in the C-terminal domain of the prototype foamy viral (PFV) integrase (IN) protein that were essential for viral replication. We constructed seven point mutants in the C-terminal domain by changing the lysine and arginine at residues 305, 308, 313, 315, 318, 324, and 329 to threonine or proline, respectively, to identify residues conferring NLS activity. Our results showed that mutation of these residues had no effect on expression assembly, release of viral particles, or in vitro recombinant IN enzymatic activity. However, mutations at residues 305 (R → T), 313(R → T), 315(R → P), and 329(R → T) lead to the production of defective viral particles with loss of infectivity, whereas non-defective mutations at residues 308(R → T), 318(K → T), and 324(K → T) did not show any adverse effects on subsequent production or release of viral particles. Sub-cellular fractionation and immunostaining for viral protein PFV-IN and PFV-Gag localization revealed predominant cytoplasmic localization of PFV-IN in defective mutants, whereas cytoplasmic and nuclear localization of PFV-IN was observed in wild type and non-defective mutants. However sub-cellular localization of PFV-Gag resulted in predominant nuclear localization and less presence in the cytoplasm of the wild type and non-defective mutants. But defective mutants showed only nuclear localization of Gag. Therefore, we postulate that four basic arginine residues at 305, 313, 315 and 329 confer the karyoplilic properties of PFV-IN and are essential for successful viral integration and replication.

Development of puffed ginseng-rice snack from ginseng powder and map rice flour using steam and compression process

A new manufacturing method for producing a puffed ginseng-rice snack (PGRS) was developed using ginseng powder and map rice flour through a steam and compression process (SCP). The physical and sensory properties of the PGRS were characterized. The pellets for puffing were prepared from ginseng powder and map rice flour. The pellets were subjected to 16, 18, and 20% moisture contents and were puffed at 225, 235, and 245° C. The specific volumes of the PGRSs increased with heating temperature and moisture content. However, the breaking strength of the PGRSs decreased. In addition, the SCP imposed special features in the PGRSs that made them more acceptable. The Hunter L-value increased with heating temperature and moisture content. These results indicate that a PGRS with functional additives could be effectively developed into a functional food with the use of a puffing machine, and that the PGRS shows potential as a new snack product.

Biochemical characteristics of functional domains using feline foamy virus integrase mutants

We constructed deletion mutants and seven point mutants by polymerase chain reaction to investigate the specificity of feline foamy virus integrase functional domains. Complementation reactions were performed for three enzymatic activities such as 3'-end processing, strand transfer, and disintegration. The complementation reactions with deletion mutants showed several activities for 3'-end processing and strand transfer. The conserved central domain and the combination of the N-terminal or C-terminal domains increased disintegration activity significantly. In the complementation reactions between deletion and point mutants, the combination between D107V and deletion mutants revealed 3'-end processing activities, but the combination with others did not have any activity, including strand transfer activities. Disintegration activity increased evenly, except the combination with glutamic acid 200. These results suggest that an intact central domain mediates enzymatic activities but fails to show these activities in the absence of the N-terminal or C-terminal domains.

Minimal size of prototype foamy virus integrase for nuclear localization

We have reported previously that the prototype foamy virus (PFV) integrase (IN) has a strong nuclear localization signal (NLS) in its C-terminal domain, in particular in a region of aa 306-334 including highly karyophilic arginines or lysines at positions 308, 313, 318, 324, and 329. In this study, we used various mutants of the C-terminal domain to further analyze its karyophilic determinants. Plasmids expressing these mutants fused to maltose binding protein (MBP) and enhanced green fluorescent protein (EGFP) were transfected to COS-1 cells and subcellular localization of these fluorescent fusion proteins was determined by fluorescent microscopy. The results revealed that a maximum karyophilicity was exhibited by a region longer than the previously described one of 29 aa (aa 306-334), in particular by a 64 aa region (aa 289-352) with Arg341 and Lys349 as critical determinants.

Characterization of biochemical properties of feline foamy virus integrase

In order to study biochemical properties, the integrase (IN) protein of feline foamy virus (FFV) was over-expressed from Escherichia coli, purified by two-step chromatography; Talon column and heparin column, and characterized in biochemical aspects. For the three enzymatic reactions of the 3' -processing, strand transfer, and disintegration activities, Mn2+ ion was essentially required as a cofactor. Interestingly, Co2+ and Zn2+ ions were found to act as effective cofactors, while other transition elements such as Ni2+, Cu2+, La3+, Y3+, Cd2+, Li1+, Ba2+, Sr2+, V3+, and so on were not. Regarding to the substrate specificity, FFV IN has low substrate specificities as it cleaved in a significant level prototype foamy virus (PFV) U5 LTR substrate as well as FFV U5 LTR substrate, while PFV IN did not. Finally, the 3' -processing activity was observed in the high concentrations of several solvents such as CHAPS, Glycerol, Tween 20 and Triton X-100, which are generally used for dissolution of chemicals in inhibitor-screening. Therefore, as it is the first report showing biochemical properties, FFV IN is proposed to have low specificities on the use of cofactor and substrate for enzymatic reaction when it is compared with other retroviral INs.

Beauvericin and enniatins H, I and MK1688 are new potent inhibitors of human immunodeficiency virus type-1 integrase

Some enniatins (ENs) reportedly exhibit antiretroviral activities in vivo. The potential inhibitory activities of cyclic hexadepsipeptides such as beauvericin (BEA) and ENs H, I and MK1688 were investigated in vitro against human immunodeficiency virus type-1 (HIV-1) integrase and Moloney murine leukemia virus reverse transcriptase. BEA, EN I and EN MK1688 exhibited strong inhibitory activities against HIV-1 integrase, whereas EN H showed relatively weak activity. None of the examined compounds showed anti-reverse transcriptase activity. BEA was the most effective inhibitor of the tested cyclic hexadepsipeptides in inhibiting HIV-1 integrase. These results indicate the potential of cyclic hexadepsipeptides as a new class of potent inhibitors of HIV-1 integrase.

Characterization of nuclear localization signals of the prototype foamy virus integrase

To analyse the potential karyophilic activity of prototype foamy viruses (PFVs), we expressed the PFV integrase (IN) and its mutants as fusion proteins with enhanced green fluorescence protein. The subcellular localization of the fusion proteins was investigated by fluorescence microscopy. The PFV IN was found to be karyophilic and targeted the fusion protein to the nucleus. Mutational analyses demonstrated that the PFV IN contains a potent but non-transferable nuclear localization signal (NLS) in its C-terminal domain and contains five arginine and lysine residues between amino acids 308 and 329 that are critical for its NLS function.

Functional nucleotides of U5 LTR determining substrate specificity of prototype foamy virus integrase

In order to study functional nucleotides in prototype foamy virus (PFV) DNA on specific recognition by PFV integrase (IN), we designed chimeric U5 long terminal repeat (LTR) DNA substrates by exchanging comparative sequences between human immunodeficiency virus type-1 (HIV-1) and PFV U5 LTRs, and investigated the 3'-end processing reactivity using HIV-1 and PFV INs, respectively. HIV-1 IN recognized the nucleotides present in the fifth and sixth positions at the 3'-end of the substrates more specifically than any other nucleotides in the viral DNA. However, PFV IN recognized the eighth and ninth nucleotides as distinctively as the fifth and sixth nucleotides in the reactions. In addition, none of the nucleotides present in the twelfth, sixteenth, seventeenth, eighteenth, nineteenth, and twentieth positions were not differentially recognized by HIV-1 and PFV INs, respectively. Therefore, our results suggest that the functional nucleotides that are specifically recognized by its own IN in the PFV U5 LTR are different from those in the HIV-1 U5 LTR in aspects of the positions and nucleotide sequences. Furthermore, it is proposed that the functional nucleotides related to the specific recognition by retroviral INs are present inside ten nucleotides from the 3'-end of the U5 LTR.

Statistical optimization of growth medium for the production of the entomopathogenic and phytotoxic cyclic depsipeptide beauvericin from Fusarium oxysporum KFCC 11363P

The production of the entomopathogenic and phytotoxic cyclic depsipeptide beauvericin (BEA) was studied in submerged cultures of Fusarium oxysporum KFCC 11363P isolated in Korea. The influences of various factors on mycelia growth and BEA production were examined in both complete and chemically defined culture media. The mycelia growth and BEA production were highest in Fusarium defined medium. The optimal carbon and nitrogen sources for maximizing BEA production were glucose and NaNO3, respectively. The carbon/ nitrogen ratio for maximal production of BEA was investigated using response surface methodology (RSM). Equations derived by differentiation of the RSM model revealed that the production of BEA was maximal when using 108 mM glucose and 25 mM NaNO3.

Caffeoylglycolic and caffeoylamino acid derivatives, halfmers of L-chicoric acid, as new HIV-1 integrase inhibitors

Human immunodeficiency virus (HIV) integrase (IN) catalyzes the integration of HIV DNA copy into the host cell DNA. L-Chicoric acid (1) has been found to be one of the most potent HIV-1 integrase inhibitor. Caffeoylglycolic and caffeoylamino acid derivatives' halfmeric structures of L-chicoric acid 2 were synthesized for the purpose of simplifying the structure of L-chicoric acid. Among synthesized, compounds 2c and 3f showed HIV-1 IN inhibitory activities with IC(50) values of 10.5 and 12.0 microM, respectively, comparable to that of parent compound L-chicoric acid (IC(50)=15.7 microM).

Enhanced ginsenoside productivity by combination of ethephon and methyl jasmoante in ginseng (Panax ginseng C.A. Meyer) adventitious root cultures

Ethephon at 50 microM enhanced both root growth and ginsenoside accumulation in ginseng (Panax ginseng C.A. Meyer) adventitious root cultures, but at 100 microM it inhibited only ginsenoside accumulation. Ginsenoside productivity with 50 microM ethephon was the highest at 1.7 mg l(-1) d(-1) after 8 days of elicitation. However, elicitation with 50 microM ethephon and 100 microM methyl jasmonate (MJ) improved productivity (6.3 mg l(-1) d(-1)) whereas elicitation with 100 microM MJ alone gave only 2.9 mg l(-1) d(-1).

Vanillic acid glycoside and quinic acid derivatives from Gardeniae Fructus

Bioassay-directed chromatographic fractionation of an ethyl acetate extract of Gardenia jasminoides (Gardeniae Fructus) afforded a new vanillic acid 4-O-beta-d-(6'-sinapoyl)glucopyranoside (1) and five new quinic acid derivatives, methyl 5-O-caffeoyl-3-O-sinapoylquinate (2), ethyl 5-O-caffeoyl-3-O-sinapoylquinate (3), methyl 5-O-caffeoyl-4-O-sinapoylquinate (4), ethyl 5-O-caffeoyl-4-O-sinapoylquinate (5), and methyl 3,5-di-O-caffeoyl-4-O-(3-hydroxy-3-methyl)glutaroylquinate (6), together with three known quinic acid derivatives, two flavonoids, two iridoids, and two phenolic compounds. The structures of new compounds were elucidated by the aid of spectroscopic methods. These compounds were assessed for antioxidant activity using three different cell-free bioassay systems and for HIV-1 integrase inhibitory activity. Five new quinic acid derivatives showed potent DPPH radical scavenging, superoxide anion scavenging, and lipid peroxidation inhibition activities. These new quinic acid derivatives also exhibited HIV-1 integrase inhibitory activity.

Characterization of the functional domains of human foamy virus integrase using chimeric integrases

Retroviral integrases insert viral DNA into target DNA. In this process they recognize their own DNA specifically via functional domains. In order to analyze these functional domains, we constructed six chimeric integrases by swapping domains between HIV-1 and HFV integrases, and two point mutants of HFV integrase. Chimeric integrases with the central domain of HIV-1 integrase had strand transfer and disintegration activities, in agreement with the idea that the central domain determines viral DNA specificity and has catalytic activity. On the other hand, chimeric integrases with the central domain of HFV integrase did not have any enzymatic activity apart from FFH that had weak disintegration activity, suggesting that the central domain of HFV integrase was defective catalytically or structurally. However, these inactive chimeras were efficiently complemented by the point mutants (D164A and E200A) of HFV integrase, indicating that the central domain of HFV integrase possesses potential enzymatic activity but is not able to recognize viral or target DNA without the help of its homologous N-terminal and C-terminal domains.

Overexpression of squalene synthase in Eleutherococcus senticosus increases phytosterol and triterpene accumulation

Squalene synthase (SS) catalyzes the first committed step in sterol and triterpenoid biosynthesis. Transgenic Eleutherococcus senticosus Rupr. and Maxim. plants were generated by introducing an SS-encoding gene derived from Panax ginseng (PgSS1) together with genes expressing hygromycin phosphotransferase and green fluorescent protein (GFP) through Agrobacterium-mediated transformation. Early globular embryo clusters developing from the embryogenic callus were used for Agrobacterium-mediated transformation. Transformants were selected on Murashige Skoog medium containing 25 mg/L hygromycin. Hygromycin-resistant somatic embryos developed into plants after the cotyledonary embryos were treated with 14.4 microM gibberellic acid. Transformation was confirmed by polymerase chain reaction, Southern, and GFP analyses. The SS enzyme activity of the transgenic plants was up to 3-fold higher than that of wild-type plants. In addition, GC-MS and HPLC analysis revealed that phytosterols (beta-sitosterol and stigmasterol) as well as triterpene saponins (ciwujianosides B (1), C(1) (2), C(2) (3), C(3) (4), C(4) (5), D(1) (6) and D(2) (7)) levels in transgenic E. senticosus were increased by 2- to 2.5-fold. These results suggest that the metabolic engineering of E. senticosus to enhance production of phytosterols and triterpenoids by introducing the PgSS1 gene was successfully achieved by Agrobacterium-mediated genetic transformation.

Enhanced Triterpene and Phytosterol Biosynthesis in Panax ginseng Overexpressing Squalene Synthase Gene

Roots of Panax ginseng, one of the most famous medicinal plants, contain various phytosterols and bioactive triterpene saponins (ginsenosides). In P. ginseng, phytosterols and triterpenes share the common biosynthetic intermediate, squalene. Here, we investigate the regulatory role of Panax ginseng squalene synthase (PgSS1) on the biosynthesis of phytosterols and triterpene saponins. PgSS1 transcripts are expressed ubiquitously in the various plant tissues, but higher in shoot apex and root. The transcript levels of PgSS1 increased markedly in the adventitious roots during 12- to 96-h period after metyl jasmonate (MeJA) treatment; MeJA treatment induced the activation of the transcripts of squalene epoxidase (SE), beta-amyrin synthase (bAS), but not cycloartenol synthase (CAS). Unlike MeJA treatment, overexpression of PgSS1 in adventitious roots of transgenic P. ginseng was followed by the up-regulation of all the downstream genes tested, such as SE, bAS, and CAS. The enhanced activity of PgSS1 enzyme resulted in remarkable increase of phytosterols as well as ginsenoside contents. These results demonstrate that PgSS1 is a key regulatory enzyme not only for phytosterol but also for triterpene biosynthesis and overexpressing of PgSS1 confers the hyperproduction of triterpene saponins to P. ginseng.

DA-125, a new antitumor agent, inhibits topoisomerase ii as topoisomerase poison and dna intercalator simultaneously

DA-125, a novel derivative of adriamycin, is known for its anti-cancer activity. In this study, the inhibitory mechanism of DA-125 on topoisomerase was investigated in the simian virus 40 (SV40) replicating CV-1 cell by studying the SV40 DNA replication intermediates and DNA-topoisomerase complexes. DNA-protein complexes that were formed in the drug-treated cells were quantitated by using a glass filter assay. SV40 DNA replication intermediates that were accumulated in the drug-treated CV-1 cell were analyzed in a high resolution gel. DA-125 did not accumulate B-dimers of SV40 DNA replication intermediates which were found in the adriamycin-treated CV-1 cells. DA-125 induced a dose-dependent formation of the DNA-protein complexes, while adriamycin did not. When adriamycin and etoposide (VP16) were added to the SV40-infected cells at the same time, adriamycin blocked the formation of the DNA-protein complexes induced by VP16 in a dose-dependent manner. However, DA-125 blocked the formation of the DNA-protein complexes induced by VP16 up to the maximum level of the DNA-protein complexes that were induced by DA-125 alone. Adriamycin and DA-125 did not inhibit the formation of the DNA-protein complexes that were caused by camptothecin, a known topoisomerase I poison. DA-125 is bifunctional in inhibiting topoisomerase II because it simultaneously has the properties of the topoisomerase II poison and the DNA intercalator. As a topoisomerase II poison, DA-125 alone induced dose-dependent formation of the DNA-protein complexes. However, as a DNA intercalator, it quantitatively inhibited the formation of the DNA-protein complexes induced by a strong topoisomerase II poison VP16. Furthermore considering that the levels of the DNA-protein complex induced by VP16 were decreased by DA-125 in terms of the topoisomerase II poison, we suggest that DA-125 has a higher affinity to the drug-binding sites of DNA than VP16 has.

Caffeoyl naphthalenesulfonamide derivatives as HIV integrase inhibitors

HIV-1 integrase (IN) is an essential enzyme for retroviral replication and a rational target for the design of anti-AIDS drugs. In the present study, we have designed, synthesized and tested a series of caffeoyl naphthalenesulfonamide derivatives as HIV integrase inhibitors. Among these compounds, we found that HIV integrase inhibitory activities of compounds III-3 and III-4 were more potent than L-chicoric acid (IC(50)=11.8 microg/mL) and others were comparable to L-chicoric acid. Furthermore, the structure-activity relationships of these compounds were studied. The information gathered from this paper will be useful in the development and design of HIV-1 integrase inhibitors in the future.

Inhibition of HIV-1 integrase by galloyl glucoses from Terminalia chebula and flavonol glycoside gallates from Euphorbia pekinensis

The bioassay-directed isolation of Terminalia chebula fruits afforded four human immunodeficiency virus type 1 (HIV-1) integrase inhibitors, gallic acid ( 1) and three galloyl glucoses ( 2 - 4). In addition, four flavonol glycoside gallates ( 5 - 8) from Euphorbia pekinensis containing the galloyl moiety also showed the inhibitory activity at a level comparable to those of 2 - 4. By comparison with the activities of the compounds not bearing this moiety, it is proposed that the galloyl moiety plays a major role for inhibition against the 3'-processing of HIV-1 integrase of these compounds.

Role of the nonspecific DNA-binding region and alpha helices within the core domain of retroviral integrase in selecting target DNA sites for integration

Retroviral integrase plays an important role in choosing host chromosomal sites for integration of the cDNA copy of the viral genome. The domain responsible for target site selection has been previously mapped to the central core of the protein (amino acid residues 49-238). Chimeric integrases between human immunodeficiency virus type 1 (HIV-1) and feline immunodeficiency virus (FIV) were prepared to examine the involvement of a nonspecific DNA-binding region (residues 213-266) and certain alpha helices within the core domain in target site selection. Determination of the distribution and frequency of integration events of the chimeric integrases narrowed the target site-specifying motif to within residues 49-187 and showed that alpha 3 and alpha 4 helices (residues 123-166) were not involved in target site selection. Furthermore, the chimera with the alpha 2 helix (residues 118-121) of FIV identity displayed characteristic integration events from both HIV-1 and FIV integrases. The results indicate that the alpha 2 helix plays a role in target site preference as either part of a larger or multiple target site-specifying motif.

Binding aspects of baicalein to HIV-1 integrase

Human immunodeficiency virus type 1 (HIV-1) integrase is an essential enzyme in the life cycle of the virus. It is responsible for catalyzing the insertion of the viral genome into the host cell chromosome. This integrase is an attractive target for the design of a HIV antiviral drug, because integrase has no human counterpart. In order to know the interaction mode of HIV-1 integrase with its inhibitor, we investigated the effect of the inhibitor, baicalein, on the conformation of the HIV-1 integrase catalytic domain [IN-(50-212/F185K)] using fluorescence and circular dichroism (CD) spectroscopy. We found that baicalein binds to the hydrophobic region of the HIV-1 integrase catalytic core domain. This binding of baicalein induces the conformational change of the enzyme. We also found that the binding ratio of baicalein to the HIV-1 integrase catalytic domain is 2:1.

HIV-1 integrase inhibitory phenylpropanoid glycosides from Clerodendron trichotomum

Seven phenylpropanoid glycosides named acteoside (1), acteoside isomer (2), leucosceptoside A (3), plantainoside C (4), jionoside D (5), martynoside (6), and isomartynoside (7) were isolated from Clerodendron trichotomum. Compounds 1 and 2 showed potent inhibitory activities against HIV-1 integrase with IC50 values of 7.8 +/- 3.6 and 13.7 +/- 6.0 microM, respectively.

A new caffeoyl quinic acid from aster scaber and its inhibitory activity against human immunodeficiency virus-1 (HIV-1) integrase

The phytochemical study of the aerial parts of Aster scaber Thunb. (Asteraceae) yielded a new caffeoyl quinic acid, (-) 3,5-dicaffeoyl-muco-quinic acid (2) and three known compounds, (-) 3,5-dicaffeoyl quinic acid (1), (-) 4,5-dicaffeoyl quinic acid (3), (-) 5-caffeoyl quinic acid (4). The structures were established by high resolution spectroscopic methods. The antiviral effects against HIV-1 integrase of the compounds was evaluated. (-) 3,5-Dicaffeoyl-muco-quinic acid (2) exhibited potent antiviral activity with an IC50 value of 7.0 +/- 1.3 microg/ml.

Synthesis and HIV-1 integrase inhibitory activities of caffeoylglucosides

Caffeoylglucosides, which have a glucose ring as a central linker, were synthesized from methyl D-glucosides, and their anti-HIV-1 activities were tested. Among them, four dicaffeoylglucosides (IC50 = 29.1+/-35.1 microM), 6a, 6b, 9b and 10b, showed HIV-1 integrase inhibitory activity as potent as L-chicoric acid.

Minimal core domain of HIV-1 integrase for biological activity

The human immunodeficiency virus type-1 (HIV-1) integrase (IN) mediates insertion of viral DNA into human DNA, which is an essential step in the viral life cycle. In order to study minimal core domain in HIV-1 IN protein, we constructed nine deletion mutants by using PCR amplification. The constructs were expressed in Escherichia coli, and the proteins were subsequently purified and analyzed in terms of biological activity such as enzymatic and DNA-binding activities. The mutant INs with an N-terminal or C-terminal deletion showed strong disintegration activity though they failed to show endonucleolytic and strand transfer activities, indicating that the disintegration reaction does not require the fine structure of the HIV-1 IN protein. In the DNA-binding analysis using gel mobility shift assay and UV cross-linking method, it was found that both the central and C-terminal domains are essential for proper DNA-IN protein interaction although the central or C-terminal domain alone was able to be in close contact with DNA substrate. Therefore, our results suggest that the C-terminal domain act as a DNA-holding motive, which leads to proper interaction for enzymatic reaction between the IN protein and DNA.

HIV integrase inhibitory activity of Agastache rugosa

We have been screening anti-HIV integrase compounds from Korean medicinal plants by using an in vitro assay system which is mainly composed of recombinant human immunodeficiency virus type 1 integrase and radiolabeled oligonucleotides. From the above screening, the aqueous methanolic extract of the roots of Agastache rugosa exhibited a significant activity. Bioactivity-guided chromatographic fractionation of the methanolic extract resulted in the isolation of rosmarinic acid. The structure of the compound was determined by spectroscopic data and by the comparison with the reported values. The IC50 of the rosmarinic acid was approximately 10 microg/ml against HIV integrase.

Analysis of integration activity of human immunodeficiency virus type-1 integrase

The integration activity of human immunodeficiency virus type-1 (HIV-1) integrase was characterized in vitro by using pre-processed oligonucleotide substrates. The highest level of integration activity was found at pH 6.5 to 7.0, while the endonucleolytic activity was highest at pH 7.4 to 8.0. Although the endonucleolytic and integration reactions are consecutive in retroviral integration, our result indicates that the optimal conditions of the two reactions are quite different. In addition, it is suggested that the endonucleolytic and integration steps can be separated by control of the cellular physiological state in retroviral therapy. Strong integration was detected in the presence of 0.5-10 mM Mn2+ ion, but weak integration at around 10 mM Mg2+ ion. This observation explains that the Mn2+ ion is preferred to the Mg2+ ion as a cofactor in the integration reaction. Although there was no sequence-specificity in the integration site of the target DNA, integration was found to frequently occur at particular regions of the target DNA. Furthermore, the mutant integrases such as Asp116, Ser147, and Glu152, which had been reported previously, were shown to lose integration activity completely, indicating that these residues are critically involved in catalytic action.

Comparison of enzymatic activities of the HIV-1 and HFV integrases to their U5 LTR substrates

The human immunodeficiency virus type 1 (HIV-1) and human foamy virus (HFV) integrase proteins were overexpressed in Escherichia coli, and purified to a near homogeneity by one- or two-step purification scheme. The endonucleolytic, integration, and disintegration activities for the HIV-1 and HFV integrases were characterized in vitro. The endonucleolytic activities for the HIV-1 and HFV integrases were found only on their own substrates, respectively, indicating that the cognate U5 LTR sequences in the substrates is critical for specific cleavage. However, the integration and disintegration activities showed less specificity on the substrate usage. Our results suggest that the disintegration activity have more preference for substrates based on Y-shaped structure rather than on viral donor DNA sequence.

A new flavonol glycoside gallate ester from Acer okamotoanum and its inhibitory activity against human immunodeficiency virus-1 (HIV-1) integrase

Bioassay-directed chromatographic fractionation of an ethyl acetate extract of the leaves of Acer okamotoanum using HIV-1 integrase afforded a new acylated flavonol glycoside, quercetin 3-O-(2",6"-O-digalloyl)-beta-D-galactopyranoside (1), together with six known flavonol glycosides and three known phenolic compounds. The structure of the new compound was determined by spectroscopic methods. The most active compounds were quercetin 3-O-(2"-galloyl)-alpha-L-arabinopyranoside (6) and 1, which exhibited IC50 values of 18.1 +/- 1.3 and 24.2 +/- 6.6 micrograms/mL, respectively, against HIV-1 integrase.

Characterization of human immunodeficiency virus type 1 integrase mutants expressed in Escherichia coli

The eight mutant integrase (IN) proteins of human immunodeficiency virus type (HIV-1), which have a single point mutation at a highly conserved central region, were prepared, and characterized in terms of their endonucleolytic activities and disintegration activities in vitro. Mutation of two highly conserved amino acids, Asp116 or Glu152, leads to complete loss of both the activities, suggesting that these two amino acids are directly associated with enzymatic functions. In addition, the mutant of the position Ser147 was found to have highly depressed endonucleolytic activity showing that the reaction was very delayed in comparison with that of the wild type. However, significant disintegration was detected in the mutant Ser147, indicating that the enzymatic mechanisms of the endonucleolytic and disintegration activities are not exactly reverse. The integrase protein with a mutation at the conserved amino acid Asn117 or Gly118 had a slight loss of the endonucleolytic activity, while a mutation at the three positions, Tyr143, Ser153, and Lys159, had no detectable effect on their enzymatic activities. These results indicate that only a few of the conserved amino acids are critical for enzymatic activities.

Genetic analysis of the human immunodeficiency virus type 1 integrase protein

Single-amino-acid changes in a highly conserved central region of the human immunodeficiency virus type 1 (HIV-1) integrase protein were analyzed for their effects on viral protein synthesis, virion morphogenesis, and viral replication. Alteration of two amino acids that are invariant among retroviral integrases, D116 and E152 of HIV-1, as well as a mutation of the highly conserved amino acid S147 blocked viral replication in two CD4+ human T-cell lines. Mutations of four other highly conserved amino acids in the region had no detectable effect on viral replication, whereas mutations at two positions, N117 and Y143, resulted in viruses with a delayed-replication phenotype. Defects in virion precursor polypeptide processing, virion morphology, or viral DNA synthesis were observed for all of the replication-defective mutants, indicating that changes in integrase can have pleiotropic effects on viral replication.

Aphidicolin-induced topological and recombinational events in simian virus 40

Highly compacted (40S) SV40 DNA replication intermediates formed in vivo during aphidicolin exposure and immediately broke down in two stages. In the rapid initial stage, single strand DNA breaks caused loss of superhelicity in the 40S replication intermediates. This DNA breakage was accompanied by the formation of strong, permanent protein-DNA crosslinks which reached a maximum as nicking of the aberrant DNA replication intermediates was completed. These protein-associated DNA strand breaks were not repaired. In the slower second stage of breakdown, the aberrant DNA replication intermediates remained nicked and strongly associated with protein as they underwent DNA replication fork breakage and recombinational changes to produce high molecular weight forms.

Patterns of strongly protein-associated simian virus 40 DNA replication intermediates resulting from exposures to specific topoisomerase poisons

Exposure of infected CV-1 cells to specific type I and type II topoisomerase poisons caused strong protein association with distinct subsets of simian virus 40 (SV40) DNA replication intermediates. On the basis of the known specificity and mechanisms of action of these drugs, the proteins involved are assumed to be the respective topoisomerases. Camptothecin, a topoisomerase I poison, caused strong protein association with form II (relaxed circular) and form III (linear) viral genomes and replication intermediates having broken DNA replication forks but not with form I (superhelical) viral DNA or normal late replication intermediates which were present. In contrast, type II topoisomerase poisons caused completely replicated forms and late viral replication forms to be tightly bound to protein--some to a greater extent than others. Different type II topoisomerase inhibitors caused distinctive patterns of protein association with the replication intermediates present. Both intercalating and nonintercalating type II topoisomerase poisons caused a small amount of form I (superhelical) SV40 DNA to be protein-associated in vivo. The protein complex with form I viral DNA was entirely drug-dependent and strong, but apparently noncovalent. The protein associated with form I DNA may represent a drug-stabilized "topological complex" between type II topoisomerase and SV40 DNA.