Small ubiquitin-related modifier 1 is a member of the SUMO protein family. It functions in a manner similar to ubiquitin in that it is bound to target proteins as part of a post-translational modification system. However, unlike ubiquitin which targets proteins for degradation, this protein is involved in a variety of cellular processes, such as nuclear transport, transcriptional regulation, apoptosis, and protein stability. It is not active until the last four amino acids of the carboxy-terminus have been cleaved off. Several pseudogenes have been reported for this gene. Alternate transcriptional splice variants encoding different isoforms have been characterized.Sequence analysis of the corresponding gene, termed UBL1, revealed that the gene encodes a 101-amino acid polypeptide with homology to ubiquitin and other ubiquitin-like proteins.