On the Biology of Werner's Complex

Werner's Complex, as a cationic coordination complex (CCC), has hitherto unappreciated biological properties derived from its binding affinity to highly anionic biomolecules such as glycosaminoglycans (GAGs) and nucleic acids. Competitive inhibitor and spectroscopic assays confirm the high affinity to GAGs heparin, heparan sulfate (HS), and its pentasaccharide mimetic Fondaparinux (FPX). Functional consequences of this affinity include inhibition of FPX cleavage by bacterial heparinase and mammalian heparanase enzymes with inhibition of cellular invasion and migration. Werner's Complex is a very efficient condensing agent for DNA and tRNA. In proof-of-principle for translational implications, it is demonstrated to display antiviral activity against human cytomegalovirus (HCMV) at micromolar concentrations with promising selectivity. Exploitation of non-covalent hydrogen-bonding and electrostatic interactions has motivated the unprecedented discovery of these properties, opening new avenues of research for this iconic compound.

Substitution-Inert Polynuclear Platinum Complexes Act as Potent Inducers of Condensation/Aggregation of Short Single- and Double-Stranded DNA and RNA Oligonucleotides

Compounds condensing DNA and RNA molecules can essentially affect important biological processes including DNA replication and transcription. Here, this work shows with the aid of total intensity light scattering, gel electrophoresis, and atomic force microscopy (AFM) that the substitution-inert polynuclear platinum complexes (SI-PPCs), particularly [{trans-Pt(NH₃ )₂ (NH₂ (CH₂ )₆ - NH₃ ⁺ )}₂ -μ-{trans-Pt(NH₃ )₂ (NH₂ (CH₂ )₆ NH₂ )₂ }]⁸⁺ (Triplatin NC), exhibit an unprecedented high potency to condense/aggregate fragments of DNA and RNA as short as 20 base pairs. SI-PPCs condensates are distinctive from those generated by the naturally occurring polyamines (commonly used DNA compacting/condensing agents). Collectively, the results further confirm that SI-PPCs are very efficient inducers of condensation of DNA and RNA, including their short fragments that might have potential in gene therapy, biotechnology, and bionanotechnology. Moreover, the data confirm the structural advantages of the phosphate clamp, with a well-defined rigid DNA recognition motif in initiating condensation and aggregation phenomena on oligonucleotides.

Substitution-Inert Polynuclear Platinum Complexes That Inhibit the Activity of DNA Polymerase in Triplex-Forming Templates

The formation of triple-helical DNA is implicated in the regulation of gene expression. The triplexes are, however, unstable under physiological conditions so that effective stabilizers for the triplex formation are needed. Herein, we describe a new strategy for the stabilization of such triplexes that is based on antitumor substitution-inert polynuclear platinum complexes (SI-PPCs). These compounds were previously shown to bind to DNA through the phosphate clamp-a discrete mode of DNA-ligand recognition distinct from the canonical intercalation and minor-groove binding. We have found that SI-PPCs efficiently inhibit DNA synthesis by DNA polymerase in sequences prone to the formation of pyrimidine- and purine-motif triplex DNAs. Moreover, the results suggest that SI-PPCs are able to induce the formation of triple-helical DNA between duplexes and strands that are not completely complementary to each other. Collectively, these data provide evidence that SI-PPCs are very efficient stabilizers of triple-stranded DNA that might exert their action by stabilizing higher-order structures such as triple-helical DNA.

Iron(II) supramolecular helicates condense plasmid DNA and inhibit vital DNA-related enzymatic activities

The dinuclear iron(II) supramolecular helicates [Fe2 L3 ]Cl4 (L=C25 H20 N4 ) bind to DNA through noncovalent (i.e., hydrogen-bonding, electrostatic) interactions and exhibit antimicrobial and anticancer effects. In this study, we show that the helicates condense plasmid DNA with a much higher potency than conventional DNA-condensing agents. Notably, molecules of DNA in the presence of the M enantiomer of [Fe2 L3 ]Cl4 do not form intermolecular aggregates typically formed by other condensing agents, such as spermidine or spermine. The helicates inhibit the activity of several DNA-processing enzymes, such as RNA polymerase, DNA topoisomerase I, deoxyribonuclease I, and site-specific restriction endonucleases. However, the results also indicate that the DNA condensation induced by the helicates does not play a crucial role in these inhibition reactions. The mechanisms for the inhibitory effects of [Fe2 L3 ]Cl4 helicates on DNA-related enzymatic activities have been proposed.