Functions as an E3-type smo-1 ligase (PubMed:15654100, PubMed:16701625, PubMed:16549501, PubMed:25475837). Mediates smo-1 conjugation to air-2 in vitro and is required for proper chromosome alignment (PubMed:25475837). In the early embryo, specifically suppresses checkpoint activation in response to DNA damage, maybe by promoting mus-101 sumoylation (PubMed:15654100). In embryos, plays a role in determining telomere localization in the nucleus (PubMed:24297748). Protein modification; protein sumoylation. May interact with gex-3. RNAi-mediated knockdown abolishes metaphase and spindle midzone-specific smo-1 conjugation during the first embryonic mitotic division. RNAi-mediated knockdown disrupts the anchoring of telomeres to the nuclear envelope in embryos, but not in muscle nuclei (PubMed:24297748). RNAi-mediated knockdown results in ectopic tbx-2 expression in seam cells, the gut and in the syncytial hypodermis (PubMed:25873636). Belongs to the PIAS family.