Peptide Nucleic\nAcids in Saturation Transfer Difference\nNuclear Magnetic Resonance Experiments: A Simple and Valuable Tool\nfor Studying HuR–Small Molecule Complexes

Ribonucleic acid (RNA)-binding proteins (RBPs) play a\nkey role\nin regulating RNA stability, fate, function, gene expression, post-transcriptional\nmodifications, and cellular activities. Among the various RBPs identified\nto date, the Hu proteins have been the most extensively studied. Specifically,\nHuR influences several cellular processes, including cell proliferation,\ndifferentiation, and stress response, and it is frequently overexpressed\nin various solid tumors. Several HuR ligands have been identified\nso far, highlighting the druggability of such a protein. To discover\nthe novel HuR–RNA interfering agents, biophysical assays represent\na promising approach. To overcome limitations for RNA manipulation,\nin this work, we explored the use of PNA (peptide nucleic acid) as\nan RNA analogue in interaction studies. Molecular modeling simulation\nrevealed the ability of aegPNA to bind HuR and, therefore, the synthesis\nof the designed PNA was conducted. The saturation transfer difference\n(STD) nuclear magnetic resonance (NMR) technique was adopted to evaluate\nthe ability of HuR ligands to interfere with the HuR–PNA complex,\ncomparing the obtained results with RNAs. Our results evidenced that\nPNA may be considered a simple and valuable tool to analyze the interaction\nand interfering properties of HuR ligands by STD-NMR, thus improving\nthe precision and reliability of the approach.