Functions as an E3-type small ubiquitin-like modifier (SUMO) ligase, stabilizing the interaction between UBE2I and the substrate, and as a SUMO-tethering factor (   ). Mediates sumoylation of CEBPA, PARK7, HERC2, MYB, TCF4 and RNF168 (  , ). Plays a crucial role as a transcriptional coregulation in various cellular pathways, including the STAT pathway, the p53/TP53 pathway, the Wnt pathway and the steroid hormone signaling pathway . Involved in gene silencing . In Wnt signaling, represses LEF1 and enhances TCF4 transcriptional activities through promoting their sumoylations (, ). Enhances the sumoylation of MTA1 and may participate in its paralog-selective sumoylation . Binds to AT-rich DNA sequences, known as matrix or scaffold attachment regions (MARs/SARs) (By similarity). Catalyzes conjugation of SUMO2 to KAT5 in response to DNA damage, facilitating repair of DNA double-strand breaks (DSBs) via homologous recombination (HR) . Mediates sumoylation of PARP1 in response to PARP1 trapping to chromatin .
Subcellular locations: Nucleus, PML body
Colocalizes with SUMO1 and TCF7L2/TCF4 and LEF1 in a subset of PML (promyelocytic leukemia) nuclear bodies.
Highly expressed in testis and, at lower levels, in spleen, prostate, ovary, colon and peripheral blood leukocytes.