This gene encodes a member of the mammalian PIAS [protein inhibitor of activated STAT-1 (signal transducer and activator of transcription-1)] family. This member contains a putative zinc-binding motif and a highly acidic region. It inhibits STAT1-mediated gene activation and the DNA binding activity, binds to Gu protein/RNA helicase II/DEAD box polypeptide 21, and interacts with androgen receptor (AR). It functions in testis as a nuclear receptor transcriptional coregulator and may have a role in AR initiation and maintenance of spermatogenesis.