SP-RING finger found in zinc finger MIZ domain-containing protein Zmiz1, Zmiz2, and similar proteins
This family includes Zmiz1 (Zimp10) and its homolog Zmiz2 (Zimp7), both of which were initially identified in humans as androgen receptor (AR) interacting proteins and function as transcriptional co-activators. They interact with BRG1, the catalytic subunit of the SWI-SNF remodeling complex. They also associate with other hormone nuclear receptors and transcription factors, such as p53 and Smad3/Smad4, and regulate transcription of specific target genes by altering their chromatin structure. The family also includes tonalli (Tna), an ortholog identified in Drosophila. It genetically interacts with the ATP-dependent SWI/SNF and Mediator complexes, suggesting a potential role for the Zmiz proteins in chromatin remodeling. Zmiz proteins contain a highly conserved Siz/PIAS (protein inhibitor of activated signal transducer and activator of transcription) RING (SP-RING) finger, also known as msx-interacting zinc finger (Miz domain), and a strong transactivation domain within the C-terminus. The SP-RING/Miz domain is highly conserved in members of the PIAS family and confers SUMO-conjugating activity. It is a variant of RING finger, which lacks the second, fifth, and sixth zinc-binding residues of the consensus C3H2C3-/C3HC4-type RING fingers. The strong intrinsic transactivation domain facilitates Zmiz proteins to augment the transcriptional activity of nuclear hormone receptors and other transcriptional factors. They may act as transcriptional co-regulators.