Automatisierte Festphasensynthese platinierter Oligonucleotide via Nucleosidphosphonate

A Click Chemistry Approach to Targeted DNA Crosslinking with cis-Platinum(II)-Modified Triplex-Forming Oligonucleotides

Limitations of clinical platinum(II) therapeutics include systemic toxicity and inherent resistance. Modern approaches, therefore, seek new ways to deliver active platinum(II) to discrete nucleic acid targets. In the field of antigene therapy, triplex‐forming oligonucleotides (TFOs) have attracted interest for their ability to specifically recognise extended duplex DNA targets. Here, we report a click chemistry based approach that combines alkyne‐modified TFOs with azide‐bearing cis‐platinum(II) complexes—based on cisplatin, oxaliplatin, and carboplatin motifs—to generate a library of Pt^II‐TFO hybrids. These constructs can be assembled modularly and enable directed platinum(II) crosslinking to purine nucleobases on the target sequence under the guidance of the TFO. By covalently incorporating modifications of thiazole orange—a known DNA‐intercalating fluorophore—into Pt^II‐TFOs constructs, enhanced target binding and discrimination between target and off‐target sequences was achieved.

2,6-Dimercuriphenol as a Bifacial Dinuclear Organometallic Nucleobase

A C-nucleoside having 2,6-dimercuriphenol as the base moiety has been synthesized and incorporated into an oligonucleotide. NMR and UV melting experiments revealed the ability of this bifacial organometallic nucleobase surrogate to form stable dinuclear Hg^II -mediated base triples with adenine, cytosine, and thymine (or uracil) in solution as well as within a triple-helical oligonucleotide. A single Hg^II -mediated base triple between 2,6-dimercuriphenol and two thymines increased both Hoogsteen and Watson-Crick melting temperatures of a 15-mer pyrimidine⋅purine*pyrimidine triple helix by more than 10 °C relative to an unmodified triple helix of the same length. This novel binding mode could be exploited in targeting certain pathogenic nucleic acids as well as in DNA nanotechnology.

DNA-Metal Base Pairs

Recent developments show encouraging results for the use of DNA as a construction material for nanometer-sized objects. Today, however, DNA-based molecular nanoarchitectures are constructed with mainly unmodified or at best end-modified oligonucleotides, thus shifting the development of functionalized DNA structures into the limelight. One of most recent developments in this direction is the substitution of the canonical Watson-Crick base pairs by metal complexes. In this way "metal-base pairs" are created, which could potentially impart magnetic or conductive properties to DNA-based nanostructures. This review summarizes research which started almost 45 years ago with the investigation of how metal ions interact with unmodified DNA and which recently culminated in the development of artificial ligand-like nucleobases so far able to coordinate up to ten metal ions inside a single DNA duplex in a programmable fashion.

Monofunctionally trans-diammine platinum(II)-modified peptide nucleic acid oligomers: a new generation of potential antisense drugs

A solid-phase approach is described that provides facile access to monofunctionally trans-PtII-modified PNA oligomers of arbitrary sequence for potential use both in antigene and antisense strategies. The approach includes the synthesis of a platinated building block 1 and its subsequent incorporation into three different PNA oligomers 5-7 by solid-phase synthesis. In a model cross-linking reaction one of the latter is found to recognize sequence-specifically a target oligonucleotide 8 and to cross-link to it. The resulting structure is the trans-PtII-cross-linked PNA/DNA duplex 9 as revealed by mass spectrometry in combination with a Maxam-Gilbert sequencing experiment.

Interstrand cross-linking reaction in triplexes containing a monofunctional transplatin-adduct

Our aim was to determine whether a single transplatin monofunctional adduct, either trans-[Pt(NH3)2(dC)Cl]+ or trans-[Pt(NH3)2(dG)Cl]+ within a homopyrimidine oligonucleotide, could further react and form an interstrand cross-link once the platinated oligonucleotide was bound to the complementary duplex. The single monofunctional adduct was located at either the 5' end or in the middle of the platinated oligonucleotide. In all the triplexes, specific interstrand cross-links were formed between the platinated Hoogsteen strand and the complementary purine-rich strand. No interstrand cross-links were detected between the platinated oligonucleotides and non-complementary DNA. The yield and the rate of the cross-linking reaction depend upon the nature and location of the monofunctional adducts. Half-lives of the monofunctional adducts within the triplexes were in the range 2-6 h. The potential use of the platinated oligonucleotides to modulate gene expression is discussed.