Auxiliary spliceosomal protein that regulates selection of alternative splice sites in a small set of target pre-mRNA species (Probable). Selectively regulates alternative splicing of unc-52 exon 17. Thus, smu-2 mutants selectively suppress the effects of unc-52 nonsense mutations in exon 17 by promoting the accumulation of unc-52 isoforms that lack exon 17. In contrast, smu-2 mutants do not suppress the effects of an unc-52 mutation that affects the 5' splice site of exon 16. Required for normal accumulation of smu-1 (PubMed:15254247). Probable component of the spliceosome (By similarity). Heterotetramer with smu-1 (PubMed:27150041). The smu-1 homodimer interacts (via the N-terminal region including the LisH and CTLH domains) with smu-2, giving rise to a heterotetramer (PubMed:15254247, PubMed:27150041). Ubiquitous. Detected at all stages of development, during early embryogenesis and in oocytes, in larvae and adults. Intrinsically disordered protein (Probable). RNAi-mediated knockdown gives rise to no visible phenotype in wild-type, but suppresses the effects of unc-52 mutations. Belongs to the RED family.