The alternative splicing program of differentiated smooth muscle cells involves concerted non-productive splicing of post-transcriptional regulators

CLARE GOODING; ADRIAN BUCKROYD; MELIS KAYIKCI; EDUARDO EYRAS; MIRIAM LLORIAN; MARTINA HALLEGGER; DIPEN RAJGOR; JERNEJ ULE; NICOLAS BELLORA; XIAO WANG; JACK FELTHAM; CHRISTOPHER SMITH

NUCLEIC ACIDS RESEARCH

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2016

0305-1048

Alternative splicing (AS) is a key component of geneexpression programs that drive cellular differentia-tion. Smooth muscle cells (SMCs) are important inthe function of a number of physiological systems;however, investigation of SMC AS has been restrictedto a handful of events. We profiled transcriptomechanges in mouse de-differentiating SMCs and ob-served changes in hundreds of AS events. Exonsincluded in differentiated cells were characterizedby particularly weak splice sites and by upstreambinding sites for Polypyrimidine Tract Binding pro-tein (PTBP1). Consistent with this, knockdown ex-periments showed that that PTBP1 represses manysmooth muscle specific exons. We also observedcoordinated splicing changes predicted to down-regulate the expression of core components of U1and U2 snRNPs, splicing regulators and other post-transcriptional factors in differentiated cells. The lev-els of cognate proteins were lower or similar in dif-ferentiated compared to undifferentiated cells. How-ever, levels of snRNAs did not follow the expressionof splicing proteins, and in the case of U1 snRNP wesaw reciprocal changes in the levels of U1 snRNAand U1 snRNP proteins. Our results suggest that theAS program in differentiated SMCs is orchestratedby the combined influence of auxiliary RNA bindingproteins, such as PTBP1, along with altered activityand stoichiometry of the core splicing machinery.