Synthesis and characterization of pseudocantharidins, novel phosphatase modulators that promote the inclusion of exon 7 into the survival of motoneuron (SMN) pre-mRNA
Zhang, Zhaiyi × Kelemen, Olga van Santen, Maria A Yelton, Sharon M Wendlandt, Alison E Sviripa, Vitali M Bollen, Mathieu Beullens, Monique Urlaub, Henning Lührmann, Reinhard Watt, David S Stamm, Stefan #
American Society for Biochemistry and Molecular Biology
Journal of Biological Chemistry vol:286 issue:12 pages:10126-10136
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 (SMA) is caused by the loss of the survival of motoneuron 1 gene (SMN1). A therapeutic avenue for SMA treatment is to promote exon 7 inclusion of the almost identical survival of motoneuron-2 (SMN2) gene. The splicing factor tra2-beta1 promotes inclusion of this exon and is antagonized by Protein Phosphatase 1 (PP1). To identify new compounds that promote exon 7 inclusion, we synthesized analogs of cantharidin, an inhibitor of PP1 and protein phosphatase 2A. 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 T33 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.