A Druglike Small Molecule that Targets r(CCUG) Repeats in Myotonic Dystrophy Type 2 Facilitates Degradation by RNA Quality Control Pathways

J Med Chem. 2021 Jun 24;64(12):8474-8485. doi: 10.1021/acs.jmedchem.1c00414. Epub 2021 Jun 8.

Abstract

Myotonic dystrophy type 2 (DM2) is one of >40 microsatellite disorders caused by RNA repeat expansions. The DM2 repeat expansion, r(CCUG)exp (where "exp" denotes expanded repeating nucleotides), is harbored in intron 1 of the CCHC-type zinc finger nucleic acid binding protein (CNBP). The expanded RNA repeat causes disease by a gain-of-function mechanism, sequestering various RNA-binding proteins including the pre-mRNA splicing regulator MBNL1. Sequestration of MBNL1 results in its loss-of-function and concomitant deregulation of the alternative splicing of its native substrates. Notably, this r(CCUG)exp causes retention of intron 1 in the mature CNBP mRNA. Herein, we report druglike small molecules that bind the structure adopted by r(CCUG)exp and improve DM2-associated defects. These small molecules were optimized from screening hits from an RNA-focused small-molecule library to afford a compound that binds r(CCUG)exp specifically and with nanomolar affinity, facilitates endogenous degradation of the aberrantly retained intron in which it is harbored, and rescues alternative splicing defects.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzothiazoles / chemical synthesis
  • Benzothiazoles / pharmacology*
  • Humans
  • Molecular Structure
  • Myotonic Dystrophy / genetics
  • Quinazolines / chemical synthesis
  • Quinazolines / pharmacology*
  • RNA / drug effects*
  • RNA / genetics
  • RNA / metabolism
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Repetitive Sequences, Nucleic Acid / genetics
  • Small Molecule Libraries / chemical synthesis
  • Small Molecule Libraries / pharmacology
  • Structure-Activity Relationship

Substances

  • Benzothiazoles
  • CNBP protein, human
  • MBNL1 protein, human
  • Quinazolines
  • RNA-Binding Proteins
  • Small Molecule Libraries
  • RNA