title: Activation and repression functions of an SR splicing regulator depend on exonic versus intronic-binding position.
abstract: SR proteins and related factors play widespread roles in alternative pre-mRNA splicing and are known to promote splice site recognition through their Arg-Ser-rich effector domains. However, binding of SR regulators to some targets results in repression of splice sites through a distinct mechanism. Here, we investigate how activated and repressed targets of the Drosophila SR regulator Transformer2 elicit its differing effects on splicing. We find that, like activation, repression affects early steps in the recognition of splice sites and spliceosome assembly. Repositioning of regulatory elements reveals that Tra2 complexes that normally repress splicing from intronic positions activate splicing when located in an exon. Protein tethering experiments demonstrate that this position dependence is an intrinsic property of Tra2 and further show that repression and activation are mediated by separate effector domains of this protein. When other Drosophila SR factors (SF2 and Rbp1) that activate splicing from exonic positions were tethered intronically they failed to either activate or repress splicing. Interestingly, both activities of Tra2 favor the exonic identity of the RNA sequences that encompass its binding sites. This suggests a model in which these two opposite functions act in concert to define both the position and extent of alternatively spliced exons.
authors.affiliation: Department of Genetics and Genes & Development Graduate Program, University of Texas MD Anderson Cancer Center, Houston, TX 77030-4009, USA.
authors.forename: Manli
authors.initials: M
authors.lastname: Shen
authors.forename: William
authors.initials: W
authors.lastname: Mattox
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D002478:Cells, Cultured; D029721:Drosophila Proteins / Q000378:metabolism*; D005091:Exons; D007438:Introns; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins / Q000378:metabolism; D038621:Regulatory Sequences, Ribonucleic Acid; D012261:Ribonucleoproteins / Q000378:metabolism*; D017381:Spliceosomes / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; C083909:RBP1 protein, Drosophila; D000072260:RNA Splicing Factors; D016601:RNA-Binding Proteins; D038621:Regulatory Sequences, Ribonucleic Acid; D012261:Ribonucleoproteins; C519409:SF2 protein, Drosophila; C066174:tra2 protein, Drosophila