LAUSR

The ubiquitin‐like protein Hub1/UBL‐5 associates with proteins non‐covalently. Hub1 promotes alternative splicing and splicing of precursor mRNAs with weak introns in yeast and mammalian cells; however, its splicing function has remained elusive in multicellular organisms. Here, we demonstrate the splicing function of Hub1/UBL‐5 in the free‐living nematode Caenorhabditis elegans. Hub1/UBL‐5 binds to the HIND‐containing splicing factors Snu66/SART‐1 and PRP‐38 and associates with other spliceosomal proteins. C. elegans hub1/ubl‐5 mutants die at the Larval 3 stage and show splicing defects for selected targets, similar to the mutants in yeast and mammalian cells. UBL‐5 complemented growth and splicing defects in Schizosaccharomyces pombe hub1 mutants, confirming its functional conservation. Thus, UBL‐5 is important for C. elegans development and plays a conserved pre‐mRNA splicing function.