The Fox-1 Family and SUP-12 Coordinately Regulate Tissue-Specific Alternative Splicing In Vivo

Abstract

Many pre-mRNAs are alternatively spliced in a tissue-specific manner in multicellular organisms. The Fox-1 family of RNA-binding proteins regulate alternative splicing by either activating or repressing exon inclusion through specific binding to UGCAUG stretches. However, the precise cellular contexts that determine the action of the Fox-1 family in vivo remain to be elucidated. We have recently demonstrated that ASD-1 and FOX-1, members of the Fox-1 family in Caenorhabditis elegans, regulate tissue-specific alternative splicing of the fibroblast growth factor receptor gene, egl-15, which eventually determines the ligand specificity of the receptor in vivo. Here we report that another RNA-binding protein, SUP-12, coregulates the egl-15 alternative splicing. By screening for mutants defective in the muscle-specific expression of our alternative splicing reporter, we identified the muscle-specific RNA-binding protein SUP-12. We identified juxtaposed conserved stretches as the cis elements responsible for the regulation. The Fox-1 family and the SUP-12 proteins form a stable complex with egl-15 RNA, depending on the cis elements. Furthermore, the asd-1; sup-12 double mutant is defective in sex myoblast migration, phenocopying the isoform-specific egl-15(5A) mutant. These results establish an in vivo model that coordination of the two families of RNA-binding proteins regulates tissue-specific alternative splicing of a specific target gene.

SUPPLEMENTAL MATERIAL

We thank T. Nojima, and A. Takeuchi at TMDU for discussion. We thank Y. Ogawa and N. Kataoka at TMDU for critically reading the paper. We thank the Caenorhabditis Genetics Center for materials. We thank M. Hagiwara and N. Sekine for technical assistance.

This work was supported by a Grant-in-Aid for Scientific Research on Priority Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan (to H.K. and M.H.).

H.K. contributed to the overall experiments. G.O. contributed to the mutant analyses. S.M. contributed to the mutant screening. H.K. and M.H. organized this work. All authors discussed the results and commented on the manuscript.