RNA-binding protein that binds to the 5'-NACUAAY-N(1,20)-UAAY-3' consensus sequence in pre-mRNA introns to promote alternative splicing (PubMed:18230701, PubMed:20573244, PubMed:23071450). Required for mutually exclusive alternative splicing where it modulates the switch between mutually exclusive exons during pre-mRNA maturation (PubMed:18230701, PubMed:23071450). Involved in muscle-specific gene expression regulating the alternative splicing of genes such as let-2 and unc-60 to ensure that their respective isoforms are expressed in muscle (PubMed:18230701, PubMed:23071450). Promotes the removal of intron 10 from let-2 pre-mRNA to allow for the exclusive expression of the muscle-specific let-2 isoform (as opposed to the non-muscle-specific isoform expressed in embryos) in body wall muscles during late larval and adult stages of development (PubMed:18230701). Binds cooperatively with RNA-binding protein sup-12 to intron 1A of the unc-60 pre-mRNA to promote alternative splicing and expression of the muscle specific isoform of unc-60 (PubMed:23071450). Interacts with sup-12; in the presence of RNA, but with weak affinity in the absence of RNA. Isoform b: Expressed in the hypodermis and pharyngeal muscles (PubMed:18230701). Isoform c: Expressed in body wall muscles and phayngeal muscles (PubMed:18230701, PubMed:23071450). Expressed during embryonic development. The KH domain and the Qua2 region are involved in RNA binding. Defective alternative splicing of the unc-60 gene which results in decreased expression of the muscle-specific isoform of unc-60 (PubMed:23071450). Double knockout with isoform c of unc-60 rescues the motility and actin filament disorganization defects in the single unc-60 isoform c mutant (PubMed:23071450). RNAi-mediated knockdown results animals that are viable throughout embryonic and larval development, and furthermore, results in defective alternative splicing of the let-2 gene, whereby transcripts containing exon 10 are not formed in larvae and so the muscle-specific isoform of let-2 is not expressed in body wall muscles (PubMed:18230701). RNAi-mediated knockdown results in abnormal ectopic expression of the non-muscle-specific isoform b of unc-60 in body wall muscles (PubMed:23071450).