Component of the SUMO-targeted ubiquitin ligase (STUbL) complex SLX5/SLX8 that mediates ubiquitination and subsequent desumoylation of sumoylated proteins and proteins containing SUMO-like domains for their degradation (PubMed:11139495, PubMed:16325482, PubMed:18032921, PubMed:17669696, PubMed:17848550, PubMed:18499666, PubMed:18948542, PubMed:31015336). The STUbL complex SLX5/SLX8 stimulates ubiquitin conjugating enzymes, including UBC1, UBC4, UBC5 and UBC13-MMS2, and mediates the proteolytic down-regulation of sumoylated proteins (PubMed:18032921). The STUbL complex SLX5/SLX8 is involved in ubiquitin-mediated degradation of histone variant CSE4, preventing mislocalization to euchromatin (PubMed:26960795). The complex plays an essential role in maintenance of chromosome stability and links SUMO-dependent ubiquitination to a centromere-specific function during mitosis (PubMed:23785440). The complex is involved in proteolysis of spindle positioning protein KAR9 and ensures correct spindle function by regulating levels of microtubule-associated proteins (PubMed:26906737). During replication, the complex helps to prevent DNA lesions via recombination and has a role in localizing the DNA damage protein DCD2 (PubMed:16325482, PubMed:17591698). The complex especially ubiquitinates the nuclease YEN1 and prevents persistent accumulation of a fraction of YEN1 associated with sites of activity in late G2/M and helps maintain the balance between pro- and anti-crossover pathways during homologous recombination (PubMed:30479332). It is also involved in ubiquitin-mediated degradation of DNA repair proteins RAD52 and RAD57 (PubMed:18032921). Finally, the complex is recruited to distinct genomic hotspots of non-H2B protein ubiquitination (ub-hotspots) by the sumoylated transcription factor-like protein EUC1 where it ubiquitinates EUC1 and presumably other targets (PubMed:31015336). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Component of the heterodimeric SUMO-targeted ubiquitin ligase (STUbL) complex composed of SLX5 and SLX8. Localizes to few distinct genomic hotspots of non-H2B protein ubiquitination (ub-hotspots). Leads to the persistence of YEN1 foci.