SP-RING finger found in protein inhibitor of activated STAT protein 2 (PIAS2) and similar proteins
PIAS2, also known as androgen receptor-interacting protein 3 (ARIP3), DAB2-interacting protein (DIP), Msx-interacting zinc finger protein (Miz1), PIAS-NY protein, protein inhibitor of activated STAT x, protein inhibitor of activated STAT2, is an E3 SUMO-protein ligase highly expressed in the testis. It functions as a transcriptional activator of BCL2 and is essential for blocking c-MYC-induced apoptosis. It also acts as a negative regulator of cell proliferation, induces expression of the cell-cycle inhibitors p15(Ink4b) and p21(Cip1), and activates transcription of the p21(Cip1) gene in response to UV irradiation. Moreover, PIAS2 associates with topoisomerase II binding protein 1 (TopBP1), an essential activator of the Atr kinase. It thus affects the activity of the Atr checkpoint. Receptor of activated C kinase 1 (RACK1), glucocorticoid receptor (GR)-interacting protein 1 (GRIP1), friend leukemia integration-I (FLI-1), and ubiquitously expressed transcript (UXT) are binding partners of PIAS2. The interaction between UXT and PIAS2 may be important for the transcriptional activation of androgen receptor (AR). PIAS2 contains an N-terminal SAP (scaffold attachment factor A/B (SAF-A/B), acinus, and PIAS) box with the LXXLL signature, a PINT motif, a specific RING finger known as Siz/PIAS (protein inhibitor of activated signal transducer and activator of transcription) RING (SP-RING) finger, and the acidic C-terminal domain.