title: Lomofungin and dilomofungin: inhibitors of MBNL1-CUG RNA binding with distinct cellular effects.
abstract: Myotonic dystrophy type 1 (DM1) is a dominantly inherited neuromuscular disorder resulting from expression of RNA containing an expanded CUG repeat (CUG(exp)). The pathogenic RNA is retained in nuclear foci. Poly-(CUG) binding proteins in the Muscleblind-like (MBNL) family are sequestered in foci, causing misregulated alternative splicing of specific pre-mRNAs. Inhibitors of MBNL1-CUG(exp) binding have been shown to restore splicing regulation and correct phenotypes in DM1 models. We therefore conducted a high-throughput screen to identify novel inhibitors of MBNL1-(CUG)12 binding. The most active compound was lomofungin, a natural antimicrobial agent. We found that lomofungin undergoes spontaneous dimerization in DMSO, producing dilomofungin, whose inhibition of MBNL1-(CUG)12 binding was 17-fold more potent than lomofungin itself. However, while dilomofungin displayed the desired binding characteristics in vitro, when applied to cells it produced a large increase of CUG(exp) RNA in nuclear foci, owing to reduced turnover of the CUG(exp) transcript. By comparison, the monomer did not induce CUG(exp) accumulation in cells and was more effective at rescuing a CUG(exp)-induced splicing defect. These results support the feasibility of high-throughput screens to identify compounds targeting toxic RNA, but also demonstrate that ligands for repetitive sequences may have unexpected effects on RNA decay.
authors.affiliation: Department of Neurology, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Jason W
authors.initials: JW
authors.lastname: Hoskins
authors.affiliation: Department of Chemistry, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Leslie O
authors.initials: LO
authors.lastname: Ofori
authors.affiliation: Department of Chemistry, Scripps Florida, Jupiter, FL 33458, USA.
authors.forename: Catherine Z
authors.initials: CZ
authors.lastname: Chen
authors.affiliation: Department of Dermatology, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Department of Neurology, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Sobczak
authors.affiliation: Department of Neurology, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nakamori
authors.affiliation: Department of Chemistry, Scripps Florida, Jupiter, FL 33458, USA.
authors.forename: Noel
authors.initials: N
authors.lastname: Southall
authors.affiliation: Department of Chemistry, Scripps Florida, Jupiter, FL 33458, USA.
authors.forename: Samarjit
authors.initials: S
authors.lastname: Patnaik
authors.affiliation: Department of Chemistry, Scripps Florida, Jupiter, FL 33458, USA.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Marugan
authors.affiliation: Department of Chemistry, Scripps Florida, Jupiter, FL 33458, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, Scripps Florida, Jupiter, FL 33458, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Austin
authors.affiliation: Department of Dermatology, University of Rochester, Rochester, NY 14642, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Disney
authors.affiliation: Division of Pre-clinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Miller
authors.affiliation: Department of Neurology, University of Rochester, Rochester, NY 14642, USA Charles_thornton@urmc.rochester.edu.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Thornton
mesh_terms: D020413:3' Untranslated Regions; D017398:Alternative Splicing / Q000187:drug effects; D019281:Dimerization; D006801:Humans; D010619:Phenazines / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D012313:RNA / Q000737:chemistry* / Q000378:metabolism*; D020871:RNA Stability / Q000187:drug effects; D016601:RNA-Binding Proteins / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D020413:3' Untranslated Regions; C493663:MBNL1 protein, human; D010619:Phenazines; D016601:RNA-Binding Proteins; C000590228:dilomofungin; C100203:lomofungin; D012313:RNA