The PIAS family of proteins was named based on the identification of the founding member, PIAS3, as a repressor of the activity of the STAT3 transcription factor (Protein Inhibitor of Activated STAT) (Chung et al. 1997). Since then, three additional family members— PIAS1, PIASy, and PIASx—have been identified and are characterized by a high degree of sequence conservation throughout the protein...