Site-Directed Modification of mRNA with Functionalized Platinum(IV)-Ammines

Developing chemical toolkits for mRNA modification has remained an immense challenge, driven by the inherent difficulties in targeting mRNA molecules. Antisense oligonucleotides (ASOs) offer a promising framework for targeting specific mRNA sequences, yet they do not possess the capacity to alter the structure of mRNA except through enzyme-mediated hydrolysis. We developed a platinum-(IV)-ASO strategy that combines the sequence specificity of ASOs with the reactivity of platinum to functionalize nucleic acids, including short RNA and mRNA, in a selective enzyme-free manner. Access to Pt-(IV)-ASO constructs was made possible by an equatorial Pt-(IV) ammine derivatization strategy, allowing for the conjugation of carboxylic acids directly to the Pt core. Reactivity with 21-mer RNA and full-length mRNA by Pt-ASO constructs was demonstrated, and the conjugated products were characterized using a suite of orthogonal techniques, such as electrophoretic mobility shift assay, MALDI-TOF MS, temperature-dependent dissociation assay, and RT-qPCR. Constructs were optimized for their reactivity and selectivity, allowing for Pt-(IV)-PMO constructs with subnanomolar IC₅₀ values in an RNA competition assay. This Pt-(IV)-ASO platform facilitates new avenues for RNA modification by providing a strategy for functionalizing nucleic acids with potential applications in molecular biology research.