Effective incorporation of 2'-O-methyl-oligoribonucleotides into liposomes and enhanced cell association through modification with thiocholesterol

Cholesterol was linked to 2'-O-methyl-oligoribonucleotides (2'-OMe-RNA) via a disulfide bond by reacting the 3'-(pyridyldithio)-modified 2'-OMe-RNA with thiocholesterol in dichloromethane-methanol solution. This ligation reaction was made possible by a novel strategy in which the highly charged oligonucleotide was rendered soluble in nonaqueous solvent through conversion to a lipophilic amidinium salt. The biodegradable lipophilic modification of 2'-OMe-RNA resulted in a large increase in incorporation of such oligonucleotides into liposomes prepared by reversephase evaporation. Furthermore, association of these modified oligonucleotides with cultured TIB 73 cells was 100-fold higher than that seen with unmodified 2'-OMe-RNA in serum-free medium and about 10 to 30-fold higher in the presence of 10% calf serum. During incubation with cells, release of the internalized oligonucleotide from the thiocholesteryl moiety can be demonstrated

Chemie von α-Aminonitrilen. XVII. Oligo(nukleodipeptamidinium)-Salze

Experiments directed towards a chemical etiology of nucleic acids aim at uncovering facts that may help us to rationalize Nature\u27s choice of the RNA structure in the evolution of a genetic system. A strategy towards finding such facts is to synthesize potential nucleic acid alternatives and to systematically compare their functional properties (base pairing, nonenzymic replication, sequence- specific catalysis) on the chemical level with those of RNA. Nucleic acid alternatives are chosen by the criterion of whether their potential for constitutional self-assembly without enzymes is judged by chemical reasoning to be comparable to, or greater than, that of RNA. Alternatives which turn out to be functional could have (but have not or may have only temporarily) been chosen as a genetic system. Alternatives that are found to be non-functional can be dropped from the list of hypothetical RNA-competitors. Parallel to our work on nucleic acid alternatives based on hexopyranose sugars, we have studied potential pairing systems that contain dipeptide derivatives instead of sugar phosphates as building blocks of their backbones. Oligo-nucleodipeptamidinium salts of the constitutional type shown in Figure 3 can be interpreted as representing oligomers of corresponding nucleodipeptide nitriles which, in turn, can be derived from dipeptidic serine nitriles. This paper summarizes our observations on the synthesis and properties of thyminyl- and adenyl-derivatives of (L)-oligo-nucleodipeptamidinium salts (up to decamers) belonging to the constitutional type shown in Figures 9 and 10. Such oligomers are soluble in aqueous medium but turn out to be sensitive to hydrolysis at pH-values above 4 (half life of dimers at pH = 6, 1-3 h at room temperature, ca. 30 h at 0 °C). Neither in UV-spectroscopically determined mixing curves (c » 11 pM, pH = 4, 4 °C, 1 M NaCl) of mixtures of hexamers that contain complementary bases, nor in CD- spectra of (1 : 1) mixtures of the corresponding decamers (similar conditions) could we observe signs of adenine-thymine base pairing. Although these observations must be considered as preliminary since they are rather limited with regard to structural variations, conditions and observation methods, the properties observed for these materials discourage the view that such oligo-nucleodipeptamidinium salts might have been competitors to RNA. EINLEITUNG »Sie (die Naturstoffe) sind das Ergebnis einer drei Milliarden Jahre dauernden Entwicklung der lebendigen Welt und haben wáhrend einer langen Zeit die Auslese der Evolution überstanden. Ich bin überzeugt, dass sie immer eine Botschaft enthalten, und dass es unsere Aufgabe ist, diese zu entziffern.« (V. Prelog

The 3D-structure of a natural inhibitor of cell adhesion molecule expression

AbstractThe three-dimensional structure of cyclopeptolide HUN-7293, a naturally-occurring inhibitor of cell adhesion molecule expression, has been determined from nuclear magnetic resonance data recorded in solution and from X-ray diffraction analysis of single crystals. The backbone conformation of HUN-7293 is characterized by two cis-peptide bonds in both the solution and crystalline state. Differences between the solution and crystal structure are visible for the orientation of some side chains and the strength of two transannular hydrogen bonds. Such structural information helps to provide insight into the molecular architecture of HUN-7293 on the atomic level and opens the way for structure-based modifications of this novel inhibitor of cell adhesion molecule expression

The translocation inhibitor CAM741 interferes with vascular cell adhesion molecule 1 signal peptide insertion at the translocon.

The cyclopeptolide CAM741 selectively inhibits cotranslational translocation of vascular cell adhesion molecule 1 (VCAM1), a process that is dependent on its signal peptide. In this study we identified the C-terminal (C-) region upstream of the cleavage site of the VCAM1 signal peptide as most critical for inhibition of translocation by CAM741, but full sensitivity to the compound also requires residues of the hydrophobic (h-) region and the first amino acid of the VCAM1 mature domain. The murine VCAM1 signal peptide, which is less susceptible to translocation inhibition by CAM741, can be converted into a fully sensitive signal peptide by two amino acid substitutions identified as critical for compound sensitivity of the human VCAM1 signal peptide. Using cysteine substitutions of non-critical residues in the human VCAM1 signal peptide and chemical cross-linking of targeted short nascent chains we show that, in the presence of CAM741, the N- and C-terminal segments of the VCAM1 signal peptide could be cross-linked to the cytoplasmic tail of Sec61beta, indicating altered positioning of the VCAM1 signal peptide relative to this translocon component. Moreover, translocation of a tag fused N-terminal to the VCAM1 signal peptide is selectively inhibited by CAM741. Our data indicate that the compound inhibits translocation of VCAM1 by interfering with correct insertion of its signal peptide into the translocon

Inhibition of vascular endothelial growth factor cotranslational translocation by the cyclopeptolide CAM741.

The cyclopeptolide CAM741 inhibits cotranslational translocation of vascular cell adhesion molecule 1 (VCAM1), which is dependent on its signal peptide. We now describe the identification of the signal peptide of vascular endothelial growth factor (VEGF) as the second target of CAM741. The mechanism by which the compound inhibits translocation of VEGF is very similar or identical to that of VCAM1, although the signal peptides share no obvious sequence similarities. By mutagenesis of the VEGF signal peptide, two important regions, located in the N-terminal and hydrophobic segments, were identified as critical for compound sensitivity. CAM741 alters positioning of the VEGF signal peptide at the translocon, and increasing hydrophobicity in the h-region reduces compound sensitivity and causes a different, possibly more efficient, interaction with the translocon. Although CAM741 is effective against translocation of both VEGF and VCAM1, the derivative NFI028 is able to inhibit only VCAM1, suggesting that chemical derivatization can alter not only potency, but also the specificity of the compounds

Protein kinase A activation inhibits DUX4 gene expression in facioscapulohumeral muscular dystrophy patient myotubes

Facioscapulohumeral muscular dystrophy (FSHD) is among the most prevalent of the adult onset muscular dystrophies. FSHD causes the loss of muscle mass and function resulting in severe debilitation and reduction in quality of life. Currently only the symptoms of FSHD can be treated and with minimal benefit. The available options are not curative and none of the treatments address the underlying cause of FSHD. Given that the genetic, epigenetic and molecular mechanisms underlying FSHD are now quite well understood and that DUX4 expression has been demonstrated to be necessary for disease onset and is largely thought to be the causative factor in FSHD, we sought to identify compounds modulating Dux4 activity in a phenotypic screen using FSHD patient derived muscle cells. This effort has led to the identification of molecules able to reduce DUX4 gene expression and hence Dux4 activity. Amongst those, β-2 adrenergic receptor agonists and phosphodiesterase inhibitors, both leading to increased cellular cAMP, were particularly effective in patient cells. We further determined that cAMP production reduces DUX4 expression through a PKA dependent mode of action in FSHD patient myotubes. These findings increase our understanding of DUX4 expression regulation in FSHD and point to potential areas of therapeutic intervention