PURPOSE: We developed a prokaryotic expression system to express the major capsid protein of Polyomavirus, VP1. Furthermore, we investigated the transport of single stranded (ss) and double stranded (ds) DNA, mediated through VP1 as drug delivery system into mouse fibroblasts. METHODS: To study DNA delivery we used two kinds of DNA, a ssDNA fragment (19mer) and dsDNA (plasmid pEGFPN1, 4.7 kb or a FITC-labelled dsDNA fragment, 1.8 kb). RESULTS: The uptake of VP1 capsoids loaded with FITC-labelled oligodeoxynucleotides (FODNs) was observed. VP1 pentamers loaded with condensates of dendrimer/dsDNA fragments (FITC-labelled) resulted in significantly higher fluorescence signal in the cytoplasm of NIH 3T3 cells in comparison to control experiments without VP1. Additionally, VP1 capsoids loaded with plasmid pEGFPN1 without dendrimers resulted in an approximately 10 fold higher transfection rate in comparison to blank DNA controls. CONCLUSIONS: Our results demonstrated the potential of VP1 capsoids as DNA delivery system. EGFP expression was significantly enhanced when plasmid DNA was delivered via VP1 capsoids, compared to control experiments with naked DNA.

3T3 Cells↗

PubMed1999

A Dictyostelium protein binds to distinct oligo(dA) x oligo(dT) DNA sequences in the C-module of the retrotransposable element DRE.

The genome of the eukaryotic microbe Dictyostelium discoideum contains some 200 copies of the nonlong-terminal repeat retrotransposon DRE. Among several unique features of this retroelement, DRE is transcribed in both directions leading to the formation of partially overlapping plus strand and minus strand RNAs. The synthesis of minus strand RNAs is controlled by the C-module, a 134-bp DNA sequence located at the 3'-end of DRE. A nuclear protein (CMBF) binds to the C-module via interaction with two almost homopolymeric 24 bp oligo(dA) x oligo(dT) sequences. The DNA-binding drugs distamycin and netropsin, which bind to A x T-rich DNA sequences in the minor groove, competed efficiently for the binding of CMBF to the C-module. The CMBF-encoding gene, cbfA, was isolated and a DNA-binding domain was mapped to a 25-kDa C-terminal region of the protein. A peptide motif involved in the binding of A x T-rich DNA by high mobility group-I proteins ('GRP' box) was identified in the deduced CMBF protein sequence, and exchange of a consensus arginine residue for alanine within the CMBF GRP box abolished the interaction of CMBF with the C-module. The current data support the theory that CMBF binds to the C-module by detecting its long-range DNA conformation and interacting with A x T base pairs in the minor groove of oligo(dA) x oligo(dT) stretches.

Amino Acid Sequence↗

PubMed1999

Non-LTR retrotransposons with unique integration preferences downstream of Dictyostelium discoideum tRNA genes.

Retrotransposable elements are genetic enti ties which move and replicate within host cell genomes We have previously reported on the structures and ge nomic distributions of two non-long terminal repea (non-LTR) retrotransposons, DRE and Tdd-3, in the eukaryotic microorganism Dictyostelium discoideum DRE elements are found inserted upstream, and Tdd-3 elements downstream, of transfer RNA (tRNA) genes with remarkable position and orientation specificities The data set currently available from the Dictyostelium Genome Project led to the characterisation of two repetitive DNA elements which are related to the D. discoideum non-LTR retrotransposon Tdd-3 in both their structural properties and genomic distributions. It appears from our data that in the D. discoideum genome tRNA genes are major targets for the insertion of mobilised non-LTR retrotransposons. This may be interpreted as the consequence of a process of coevolution, allowing a viable population of retroelements to transpose without being deleterious to the small microbial host genome which carries only short intergenic DNA sequences. A new nomenclature is introduced to designate all tRNA gene-targeted non-LTR retrotransposons (TREs) in the D. discoideum genome. TREs inserted 5' and 3' of tRNA genes are named TRE5 and TRE3, respectively. According to this nomenclature DRE and Tdd-3 are renamed TRE5-A and TRE3-A, respectively. The new retroelements described in this study are named TRE3-B (formerly RED) and TRE3-C.

Amino Acid Sequence↗

PubMed1998

[Gene technology and drugs].

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Amino Acid Sequence↗

PubMed1998

Tdd-3, a tRNA gene-associated poly(A) retrotransposon from Dictyostelium discoideum.

The full-length 5218-bp sequence of the mobile genetic element Tdd-3 from Dictyostelium discoideum is described. Tdd-3 encodes two overlapping open reading frames (ORFs) flanked by non-redundant, untranslated regions. The deduced amino acid sequence of ORF2 is homologous to reverse transcriptases (RTs) encoded by the class of poly(A) retrotransposons. ORF2 also encodes a putative protein domain related to the family of apurinic/apyrimidinic (AP) endonucleases, whose retroelement-encoded homologs have recently been proposed to represent the integrase function of poly(A) retrotransposons. Comparison of several genomic Tdd-3 copies revealed that element insertion is orientation specific and occurs about 100 bp downstream of tRNA genes in the D. discoideum genome. These properties of Tdd-3 suggest that the element is a tRNA gene-associated poly(A) retroelement present in the D. discoideum genome. Analysis of several cloned cDNAs derived from Tdd-3-specific plus strand RNAs indicate that the element is transcribed and polyadenylated during the growth of D. discoideum cells.

Animals↗

PubMed1998

Generation and characterization of monoclonal antibodies against the pyrrolizidine alkaloid retrorsine.

Monoclonal antibodies against retrorsine were established using a retrorsine-hemisuccinate::bovine-thyroglobuline conjugate as antigen for immunization. In competitive enzyme-linked immunoassays the specificity of the obtained antibodies was tested with 20 different pyrrolizidine alkaloids. Among these the alkaloids acetylgynuramine, gynuramine, integerrimine, neoplatyphylline, platyphylline, rosmarinine, senecionine, and seneciphylline were able to bind the antibody. There was no cross-reactivity with the alkaloids senkirkine, angeloyl-heliotridine, heliotridine, axillarine, anacrotine, monocrotaline, madurensine, otosenine, retronecine, tussilagine, triangularine, and jacoline as well as with seneciphylline N-oxide. From this antigen spectrum it can be concluded that besides the necic structure itself the dominant and discriminative epitope consists of the exocyclic ethylidene group of the various diesters.

Animals↗

PubMed1998

Expression of the rat muscarinic receptor gene m3 in Dictyostelium discoideum.

We functionally expressed the rat muscarinic m3 receptor (rm3) in the cellular slime mold Dictyostelium discoideum under the control of the homologous discoidin I gamma promoter. Cells transfected with the authentic rm3 receptor gene expressed about 100 functional receptor molecules per cell, corresponding to a Bmax for [3H]-NMS of 36 +/- 9 fmol/mg of protein in isolated membranes. Genetic fusion of the Dictyostelium contact site A (csA) leader peptide to the amino terminus of rm3 increased the receptor expression by about 17-fold. Remarkable, in [3H]-NMS ligand binding experiments performed with whole cells no characteristic saturable binding was observed and there was no significant difference in [3H]-NMS binding to whole cells of rm3 and csA/rm3 transformants. The recombinant rm3 receptor showed an about 10-fold higher affinity to the M3-selective antagonist p-F-HHSiD compared to the M2-selective antagonist AQ-RA 741, suggesting that membranes derived from transgenic D. discoideum cells may be useful for the search of new subtype-specific muscarinic receptor ligands.

Animals↗

PubMed1997

A novel, negative selectable marker for gene disruption in Dictyostelium.

The expression of an ochre suppressor mutant of the GluII(UUA) tRNA appears to be lethal to Dictyostelium, and offers a novel 'positive negative' strategy to select for targeted gene disruption by homologous recombination. Inclusion of the suppressor tRNA gene decreases the overall transformation frequency by approximately 20-fold. This increases the proportion of targeted gene disruptions to over 90%.

Animals↗

PubMed1997

Molecular cloning of a cDNA encoding the nucleosome core histone H3 from Dictyostelium discoideum by genetic screening in yeast.

The one-hybrid method for genetic screening in yeast was used to search a Dictyostelium discoideum cDNA library for DNA-binding proteins that interact with the C-module of the Dictyostelium repetitive element. The C-module was formerly shown to contain two high affinity, sequence-specific binding sites for a nuclear protein factor of unknown function (CMBF). The bait DNA sequence was bound in vivo by a cDNA-encoded protein whose derived amino acid sequence showed high homology to nucleosome core histone H3, but not to partially available CMBF sequences. The D. discoideum histone H3 homolog is encoded by a single gene and shows significant sequence variation at the amino terminus of the protein, including a triple-serine insertion not found in any other histone H3.

Amino Acid Sequence↗

PubMed1997

[How dangerous is genetic technology?].

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Animals↗

PubMed1996

A nuclear protein factor binds specifically to the 3'-regulatory module of the long-interspersed-nuclear-element-like Dictyostelium repetitive element.

The Dictyostelium repetitive element DRE integrates in a position-specific manner upstream of tRNA genes in the Dictyostelium discoideum genome. DRE has structural similarities to the group of long interspersed nuclear elements, whose replication mechanism is poorly understood. The C-module at the 3' end of DRE encodes a regulatory cis-acting sequence that contains an RNA polymerase II promoter. This promoter directs the synthesis of RNAs that are thought to play a critical role in DRE transposition. In this study, we describe the identification of a nuclear protein factor that binds to the C-module in a sequence-specific manner. The C-module-binding factor (CMBF) recognizes three DNA sequence motifs that contain homopolymeric (dT) stretches of variable lengths, but does not bind to a standard RNA polymerase II promoter from D, discoideum. Analysis of highly CMBF-enriched fractions and glycerol gradient sedimentation of CMBF suggest that the factor exists as a monomeric 115-kDa protein. Possible roles of CMBF in DRE transposition are discussed.

Animals↗

PubMed1996

Molecular cloning and sequence analysis of a cDNA encoding a cysteine proteinase inhibitor from Sorghum bicolor seedlings.

A 711-bp cDNA encoding a cysteine proteinase inhibitor (cystatin) was isolated from a cDNA library prepared from 7-10 cm Sorghum bicolor seedlings. The nearly full-length cDNA clone encodes 130 amino acid residues, which include the Gin-Val-Val-Ala-Gly motif, conserved among most of the known cystatins as a probable binding site for cysteine proteinases. The amino acid sequence of sorghum cystatin deduced from the cDNA clone shows significantly homology to those of other plant cystatins. The sorghum cystatin expressed in E. coli showed a strong papain-inhibitory activity.

Amino Acid Sequence↗

PubMed1996

Autocrine growth stimulation of human meningioma cells by platelet-derived growth factor.

The authors have previously shown that meningioma-derived conditioned medium profoundly stimulates the in vitro proliferation of meningioma cells. In this paper, self mitogenic agents found in the conditioned medium-autocrine growth-stimulatory factors actually secreted by human meningioma cells-are characterized as proteins related to the B chain of platelet-derived growth factor (PDGF) and possibly to the A chain of PDGF as well. The addition to conditioned medium of a neutralizing antibody against PDGF-BB caused a significant inhibition of the conditioned medium-stimulated DNA synthesis in all three meningioma cultures studied. A similar neutralizing effect was observed with an anti-PDGF-AA antibody in one meningioma culture studied. Gel filtration chromatography of concentrated conditioned medium from two different meningiomas using a Sephadex G-100 column revealed similar profiles from both conditioned media with a major peak of mitogenic activity against meningioma cells at a molecular weight (M(r)) of approximately 32 to 36 kD, accompanied by a minor peak at approximately 22 kD. The major peak mitogenic activity was significantly reduced by addition of an anti-PDGF-BB antibody. Western blot analysis of protein extracts from five meningioma specimens was performed using a monoclonal antibody against the B chain of PGDF, and a major band of PDGF-B immunoreactivity was detected at an M(r) of approximately 19 kD in all five meningiomas under both reducing and nonreducing conditions. Exogenous human and porcine PDGFs both exhibited a significant dose-dependent stimulation of DNA synthesis in two of three and three of five meningioma cultures examined, respectively. Although not all meningiomas investigated proved to share the biological activity associated with PDGF and these results may be preliminary, it seems that the autocrine growth-stimulatory loop established by PDGF-B-related molecules plays an important functional role in meningioma cell proliferation.

Brain Neoplasms↗