Ubiquitin-like protein that can be covalently attached to proteins as a monomer or as a lysine-linked polymer. Regulates the life cycle of promyelocytic leukemia nuclear bodies (PML-NBs). PolySUMO1P1/SUMO5 conjugation on 'Lys-160' of PML facilitates recruitment of PML-NB components, which enlarges PML-NB. SUMO1P1/SUMO5 also increases polySUMO2/3 conjugation of PML, resulting in RNF4-mediated disruption of PML-NBs. Interacts with CBX4 (PubMed:27211601). Interacts with PIAS1 (PubMed:27211601). Found in a complex with SAE2 (PubMed:27211601). Interacts with UBE2I (PubMed:27211601). Interacts with SP100 (PubMed:27211601). Interacts with HIPK2 (PubMed:27211601). Interacts with DAXX (PubMed:27211601). Interacts with PML-RARA oncoprotein; PML-RARalpha outcompetes PML for SUMO1P1/SUMO5 conjugation (PubMed:27211601). Forms prominent non-membrane-bound structures in the nucleus. High expression levels in testes and peripheral blood leukocyte (PubMed:27211601). Expressed also in lung, placenta, liver, spleen and thymus (PubMed:27211601). Cleavage of precursor form is necessary for function. Autosumoylated at Lys-18. Highly conserved among primate species, however is not detected in mice. Belongs to the ubiquitin family. SUMO subfamily. Defined as a pseudogene by HGNC. However the existence of the functional protein is supported by the inhibition of its expression and its function using siRNAs specifically targeting SUMO1P1/SUMO5.