title: Synthesis and characterization of pseudocantharidins, novel phosphatase modulators that promote the inclusion of exon 7 into the SMN (survival of motoneuron) pre-mRNA.
abstract: Alternative pre-mRNA splicing is a central element of eukaryotic gene expression. Its deregulation can lead to disease, and methods to change splice site selection are developed as potential therapies. Spinal muscular atrophy is caused by the loss of the SMN1 (survival of motoneuron 1) gene. A therapeutic avenue for spinal muscular atrophy treatment is to promote exon 7 inclusion of the almost identical SMN2 (survival of motoneuron 2) gene. The splicing factor tra2-beta1 promotes inclusion of this exon and is antagonized by protein phosphatase (PP) 1. To identify new compounds that promote exon 7 inclusion, we synthesized analogs of cantharidin, an inhibitor of PP1, and PP2A. Three classes of compounds emerged from these studies. The first class blocks PP1 and PP2A activity, blocks constitutive splicing in vitro, and promotes exon 7 inclusion in vivo. The second class has no measurable effect on PP1 activity but activates PP2A. This class represents the first compounds described with these properties. These compounds cause a dephosphorylation of Thr-33 of tra2-beta1, which promotes exon 7 inclusion. The third class had no detectable effect on phosphatase activity and could promote exon 7 via allosteric effects. Our data show that subtle changes in similar compounds can turn a phosphatase inhibitor into an activator. These chemically related compounds influence alternative splicing by distinct mechanisms.
authors.affiliation: Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA.
authors.forename: Zhaiyi
authors.initials: Z
authors.lastname: Zhang
authors.forename: Olga
authors.initials: O
authors.lastname: Kelemen
authors.forename: Maria A
authors.initials: MA
authors.lastname: van Santen
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Yelton
authors.forename: Alison E
authors.initials: AE
authors.lastname: Wendlandt
authors.forename: Vitaliy M
authors.initials: VM
authors.lastname: Sviripa
authors.forename: Mathieu
authors.initials: M
authors.lastname: Bollen
authors.forename: Monique
authors.initials: M
authors.lastname: Beullens
authors.forename: Henning
authors.initials: H
authors.lastname: Urlaub
authors.forename: Reinhard
authors.initials: R
authors.lastname: Lührmann
authors.forename: David S
authors.initials: DS
authors.lastname: Watt
authors.forename: Stefan
authors.initials: S
authors.lastname: Stamm
mesh_terms: D002478:Cells, Cultured; D002648:Child; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005091:Exons; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D008297:Male; D009134:Muscular Atrophy, Spinal / Q000235:genetics / Q000378:metabolism; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing / Q000187:drug effects* / Q000235:genetics; D055533:Survival of Motor Neuron 1 Protein / Q000235:genetics / Q000378:metabolism*; D055540:Survival of Motor Neuron 2 Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D012322:RNA Precursors; C526471:SMN1 protein, human; C526477:SMN2 protein, human; D055533:Survival of Motor Neuron 1 Protein; D055540:Survival of Motor Neuron 2 Protein; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2