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. Plays a crucial role as a transcriptional coregulation in various cellular pathways, including the STAT pathway and the steroid hormone signaling pathway. Involved in regulating STAT3 signaling via inhibiting STAT3 DNA-binding and suppressing cell growth. Monomer. Binds SUMO1 and UBE2I. Interacts with BCL11A, HMGA2, IRF1, MITF and NCOA2. Interacts with STAT5; the interaction occurs on stimulation by PRL. Interacts with GFI1; the interaction relieves the inhibitory effect of PIAS3 on STAT3- mediated transcriptional activity. Interacts with AR, PLAG1 and ZFHX3. Interacts with STAT3; the interaction occurs on stimulation by IL6, CNTF or OSM and inhibits the DNA binding activity of STAT3. By dihydrotestosterone (DHT) in prostate cancer cells. Isoform 1 is expressed in most tissues except thymus and small intestine. Isoform 3 is expressed only in brain, heart, thymus, muscle, lung, testis, lactating breast and embryonic stem cells. Belongs to the PIAS family. Note: This description may include information from UniProtKB.
Protein type: EC 6.3.2.-; Nuclear receptor co-regulator; SUMO conjugating system