DNA three-way junctions (3WJ) represent one of the simplest supramolecular DNA structures arising as intermediates in homologous recombination in the absence of replication. They are also formed transiently during DNA replication. Here we examine the ability of Fe(II)-based metallohelices to act as DNA 3WJ binders and induce DNA damage in cells. We investigated the interaction of eight pairs of enantiomerically pure Fe(II) metallohelices with four different DNA junctions using biophysical and molecular biology methods. The results show that the metallohelices stabilize all types of tested DNA junctions, with the highest selectivity for the Y-shaped 3WJ and minimal selectivity for the 4WJ. The potential of the best stabilizer of DNA junctions and, at the same time, the most selective 3WJ binder investigated in this work to induce DNA damage was determined in human colon cancer HCT116 cells. These metallohelices proved to be efficient in killing cancer cells and triggering DNA damage that could yield therapeutic benefits.

• MeSH
• DNA * chemistry   MeSH
• Nucleic Acid Conformation MeSH
• Humans MeSH
• Neoplasms * genetics   MeSH
• DNA Damage MeSH
• Ferrous Compounds MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

RNA G-quadruplexes have been suggested to play key roles in fundamental biological processes and are linked to human diseases. Thus, they also represent good potential therapeutic targets. Here, we describe, using the methods of molecular biophysics, interactions of a series of biologically-active supramolecular cationic metallohelices with human telomeric RNA G-quadruplex. We demonstrate that the investigated metallohelices bind with a high affinity to human telomeric RNA G-quadruplex and that their binding selectivity considerably differs depending on the dimensions and overall shape of the metallohelices. Additionally, the investigated metallohelices inhibit DNA synthesis on the RNA template containing four repeats of the human telomeric sequence by stabilizing the RNA G-quadruplex structure. Collectively, the results of this study suggest that stabilization of RNA sequences capable of G-quadruplex formation by metallohelices investigated in this work might contribute to the mechanism of their biological activity.

• MeSH
• DNA chemistry   metabolism   MeSH
• G-Quadruplexes * MeSH
• Nucleic Acid Conformation MeSH
• Humans MeSH
• RNA chemistry   metabolism   MeSH
• Telomere metabolism   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Some metallo-supramolecular helical assemblies with size, shape, charge and amphipathic architectures similar to short cationic α-helical peptides have been shown to target and stabilise DNA G-quadruplexes (G4s) in vitro and downregulate the expression of G4-regulated genes in human cells. To expand the library of metallohelical structures that can act as efficient DNA G4 binders and downregulate genes containing G4-forming sequences in their promoter regions, we investigated the interaction of the two enantiomeric pairs of asymmetric Fe(II) triplex metallohelices with a series of five different DNA G4s formed by the human telomeric sequence (hTelo) and in the promoter regions of c-MYC, c-KIT, and k-RAS oncogenes. The metallohelices display preferential binding to G4s over duplex DNA in all investigated G4-forming sequences and induced arrest of DNA polymerase on template strands containing G4-forming sequences. Moreover, the investigated metallohelices suppressed the expression of c-MYC and k-RAS genes at mRNA and protein levels in HCT116 human cancer cells, as revealed by RT-qPCR analysis and western blotting.

• MeSH
• DNA chemistry   MeSH
• G-Quadruplexes * MeSH
• Humans MeSH
• Neoplasms * MeSH
• Oncogenes MeSH
• Promoter Regions, Genetic MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

Loss of a base in DNA leading to creation of an abasic (AP) site leaving a deoxyribose residue in the strand, is a frequent lesion that may occur spontaneously or under the action of various physical and chemical agents. Progress in the understanding of the chemistry and enzymology of abasic DNA largely relies upon the study of AP sites in synthetic duplexes. We report here on interactions of diastereomerically pure metallo-helical 'flexicate' complexes, bimetallic triple-stranded ferro-helicates [Fe2(NN-NN)3](4+) incorporating the common NN-NN bis(bidentate) helicand, with short DNA duplexes containing AP sites in different sequence contexts. The results show that the flexicates bind to AP sites in DNA duplexes in a shape-selective manner. They preferentially bind to AP sites flanked by purines on both sides and their binding is enhanced when a pyrimidine is placed in opposite orientation to the lesion. Notably, the Λ-enantiomer binds to all tested AP sites with higher affinity than the Δ-enantiomer. In addition, the binding of the flexicates to AP sites inhibits the activity of human AP endonuclease 1, which is as a valid anticancer drug target. Hence, this finding indicates the potential of utilizing well-defined metallo-helical complexes for cancer chemotherapy.

• MeSH
• 2-Aminopurine analysis   MeSH
• Amiloride analysis   MeSH
• Antineoplastic Agents chemistry   MeSH
• Nucleic Acid Denaturation MeSH
• DNA Footprinting MeSH
• DNA-(Apurinic or Apyrimidinic Site) Lyase antagonists & inhibitors   MeSH
• DNA chemistry   MeSH
• Enzyme Inhibitors chemistry   MeSH
• Calorimetry MeSH
• DNA Damage * MeSH
• Binding Sites MeSH
• Ferrous Compounds chemistry   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

The design of efficient and safe gene delivery vehicles remains a major challenge for the application of gene therapy. Of the many reported gene delivery systems, metal complexes with high affinity for nucleic acids are emerging as an attractive option. We have discovered that certain metallohelices-optically pure, self-assembling triple-stranded arrays of fully encapsulated Fe-act as nonviral DNA delivery vectors capable of mediating efficient gene transfection. They induce formation of globular DNA particles which protect the DNA from degradation by various restriction endonucleases, are of suitable size and electrostatic potential for efficient membrane transport and are successfully processed by cells. The activity is highly structure-dependent-compact and shorter metallohelix enantiomers are far less efficient than less compact and longer enantiomers.

• MeSH
• Cell Line MeSH
• DNA chemistry   ultrastructure   MeSH
• Gene Expression MeSH
• Fluorescent Antibody Technique MeSH
• Genetic Vectors * chemistry   ultrastructure   MeSH
• Cations chemistry   MeSH
• Metal Nanoparticles chemistry   ultrastructure   MeSH
• Humans MeSH
• Microscopy, Atomic Force methods   MeSH
• Molecular Structure MeSH
• Flow Cytometry MeSH
• Genes, Reporter MeSH
• Gene Transfer Techniques * MeSH
• Transfection MeSH
• Cell Survival MeSH
• Ferrous Compounds chemistry   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH