Mechanistic studies of a small-molecule modulator of SMN2 splicing

Proc Natl Acad Sci U S A. 2018 May 15;115(20):E4604-E4612. doi: 10.1073/pnas.1800260115. Epub 2018 Apr 30.


RG-7916 is a first-in-class drug candidate for the treatment of spinal muscular atrophy (SMA) that functions by modulating pre-mRNA splicing of the SMN2 gene, resulting in a 2.5-fold increase in survival of motor neuron (SMN) protein level, a key protein lacking in SMA patients. RG-7916 is currently in three interventional phase 2 clinical trials for various types of SMA. In this report, we show that SMN-C2 and -C3, close analogs of RG-7916, act as selective RNA-binding ligands that modulate pre-mRNA splicing. Chemical proteomic and genomic techniques reveal that SMN-C2 directly binds to the AGGAAG motif on exon 7 of the SMN2 pre-mRNA, and promotes a conformational change in two to three unpaired nucleotides at the junction of intron 6 and exon 7 in both in vitro and in-cell models. This change creates a new functional binding surface that increases binding of the splicing modulators, far upstream element binding protein 1 (FUBP1) and its homolog, KH-type splicing regulatory protein (KHSRP), to the SMN-C2/C3-SMN2 pre-mRNA complex and enhances SMN2 splicing. These findings underscore the potential of small-molecule drugs to selectively bind RNA and modulate pre-mRNA splicing as an approach to the treatment of human disease.

Keywords: RG-7916; RNA binding; RNA splicing; chemical proteomics; spinal muscular atrophy.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Alternative Splicing*
  • DNA Helicases / chemistry
  • DNA Helicases / genetics*
  • DNA Helicases / metabolism
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics*
  • DNA-Binding Proteins / metabolism
  • Exons
  • Humans
  • Muscular Atrophy, Spinal / genetics*
  • Muscular Atrophy, Spinal / metabolism
  • Muscular Atrophy, Spinal / pathology
  • Nucleic Acid Conformation
  • Proteomics
  • RNA Precursors / genetics*
  • RNA-Binding Proteins / chemistry
  • RNA-Binding Proteins / genetics*
  • RNA-Binding Proteins / metabolism
  • Small Molecule Libraries / pharmacology*
  • Survival of Motor Neuron 2 Protein / chemistry
  • Survival of Motor Neuron 2 Protein / genetics
  • Survival of Motor Neuron 2 Protein / metabolism
  • Trans-Activators / chemistry
  • Trans-Activators / genetics*
  • Trans-Activators / metabolism


  • DNA-Binding Proteins
  • FUBP1 protein, human
  • KHSRP protein, human
  • RNA Precursors
  • RNA-Binding Proteins
  • SMN2 protein, human
  • Small Molecule Libraries
  • Survival of Motor Neuron 2 Protein
  • Trans-Activators
  • DNA Helicases