Medicinal Chemistry & Chemical Biology, Poster
MC-116

Targeting RNA structure in SMN2 reverses Spinal Muscular Atrophy molecular phenotypes

A. Garcia-Lopez1, F. Tessaro1, H. Jonker 2, A. Wacker 2, C. Richter2, A. Comte3, B. Joseph3, H. Schwalbe2, L. Liu1*
1Pharmaceutical Biochemistry Group, School of Pharmaceutical Sciences, University of Geneva and University of Lausanne, Geneva, Switzerland, 2Institut für Organische Chemie und Chemische Biologie, Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-University Frankfurt, Frankfurt, Germany, 3Institut de Chimie et Biochimie Moléculaires et Supramoléculaires (ICBMS) UMR CNRS 5246, University of Lyon, University Claude Bernard Lyon 1, Villeurbanne, France

Modification of SMN2 exon 7 (E7) splicing to increase SMN protein production is a validated therapeutic strategy against Spinal Muscular Atrophy (SMA). Based on this, we have performed the first small molecule screening described for SMA, choosing a stem-loop RNA structure TSL2 that partially overlaps with the E7 5’ splicing site (5’ ss) of SMN2 as the biological target. TSL2-binding hit PK4C9 was found to also increase E7 splicing and rescued downstream molecular alterations in transfected HeLa cells, transgenic Drosophila, and SMA patient cells. High-resolution NMR combined with in silico modeling revealed that PK4C9 binding to TSL2 promotes a conformational shift towards a triloop conformation, which we also demonstrate that is associated with an enhanced E7 splicing efficiency. This work not only provides one of the few examples of small molecules with direct SMN2-spllicing modifier activity, but also opens new avenues for rational drug discovery in SMA and other splicing-mediated diseases where similar RNA structures are involved.