Pre-mRNA splicing function of the ubiquitin-like protein Hub1/UBL-5 in Caenorhabditis elegans

The conserved ubiquitin-like protein Hub1/UBL-5 associates with proteins non-covalently. In yeast and human cells, Hub1 promotes splicing of precursor mRNAs with weak introns and alternative splicing, however, its splicing function has remained elusive in multicellular organisms. We demonstrate the splicing function of Hub1/UBL-5 in the free-living nematode Caenorhabditis elegans. UBL-5 binds to the HIND-containing splicing factors Snu66/SART-1 and PRP-38 and associates with other spliceosomal proteins. Caenorhabditis elegans hub1/ubl-5 mutants die at the larval L3 stage, and show accumulation of intron- and outron-containing transcripts. The latter observation adds to UBL-5’s splicing function in trans-RNA splicing. UBL-5 complements splicing defects of hub1-knockout Schizosaccharomyces pombe, confirming its functional conservation. Thus, UBL-5 is important for C. elegans development and cis- and trans-RNA splicing.