SP-RING finger found in protein inhibitor of activated STAT protein 4 (PIAS4) and similar proteins
PIAS4, also known as PIASy or protein inhibitor of activated STAT protein gamma (PIAS-gamma), is an E3 SUMO-protein ligase that interacts with the androgen receptor (AR) and is involved in ubiquitin signaling pathways. It is associated with macro/microcephaly in the novel interstitial 19p13.3 microdeletion/microduplication syndrome. It also regulates the hypoxia signalling pathway by interacting with the tumor suppressor von Hippel-Lindau (VHL), which leads to VHL sumoylation, oligomerization, and impaired function during growth of pancreatic cancer cells. Moreover, PIAS4 acts as a direct binding partner for vitamin D receptor (VDR) and facilitates its modification with SUMO2. The process of SUMOylation modulates VDR-mediated signaling. As components of the DNA-damage response (DDR), PIAS4 together with PIAS1 promote responses to DNA double-strand breaks (DSBs). They are required for effective ubiquitin-adduct formation mediated by RNF8, RNF168, and BRCA1 at sites of DNA damage. PIAS4 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 an acidic C-terminal domain. The SP-RING finger is a variant of RING finger, which lacks the second, fifth, and sixth zinc-binding residues of the consensus C3H2C3-/C3HC4-type RING fingers. It binds a single Zn ion, instead of two ions bound by typical RING fingers.
Comment:based on the structures of human Sumo ligases Pias2 and Pias3 with bound Zn2+ ion through their SP-RING fingers
Comment:The SP-RING finger is a variant of RING finger; it binds a single Zn ion and lacks the second, fifth, and sixth zinc-binding residues of the consensus C3H2C3-/C3HC4-type RING fingers.
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