Antisense oligonucleotide modulation of non-productive alternative splicing upregulates gene expression

Restoration of normal gene expression is one way to treat monogenic disorders. Here the authors target naturally occurring non-productive alternative splicing using antisense oligonucleotides to promote the production of functional proteins

Phosphorylation of Myocardin by Extracellular Signal-regulated Kinase*

The contractile phenotype of smooth muscle (SM) cells is controlled by serum response factor (SRF), which drives the expression of SM-specific genes including SM α-actin, SM22, and others. Myocardin is a cardiac and SM-restricted coactivator of SRF that is necessary for SM gene transcription. Growth factors inducing proliferation of SM cells inhibit SM gene transcription, in a manner dependent on the activation of extracellular signal-regulated kinases ERK1/2. In this study, we found that ERK1/2 phosphorylates mouse myocardin (isoform B) at four sites (Ser812, Ser859, Ser866, and Thr893), all of which are located within the transactivation domain of myocardin. The single mutation of each site either to alanine or to aspartate has no effect on the ability of myocardin to activate SRF. However, the phosphomimetic mutation of all four sites to aspartate (4×D) significantly impairs activation of SRF by myocardin, whereas the phosphodeficient mutation of all four sites to alanine (4×A) has no effect. This translates to a reduced ability of the 4×D (but not of 4×A) mutant of myocardin to stimulate expression of SM α-actin and SM22, as assessed by corresponding promoter, mRNA, or protein assays. Furthermore, we found that phosphorylation of myocardin at these sites impairs its interaction with acetyltransferase, cAMP response element-binding protein-binding protein, which is known to promote the transcriptional activity of myocardin. In conclusion, we describe a novel mode of modulation of SM gene transcription by ERK1/2 through a direct phosphorylation of myocardin