PIAS2 (protein inhibitor of activated STAT 2) is an E3 SUMO ligase that functions as a transcriptional coregulator across multiple cellular pathways. It catalyzes protein sumoylation by stabilizing interactions between UBE2I and substrates, with effects varying by isoform and biological context 1. PIAS2 plays critical roles in regulating JAK-STAT signaling, p53 pathway, steroid hormone signaling, and DNA damage responses by modifying target proteins including hSSB1, MDM2, and ELK1 2. Dysregulated PIAS2 expression associates with multiple diseases. Elevated neuronal PIAS2 impairs interferon-β signaling and mitochondrial homeostasis, contributing to sporadic Parkinson disease dementia through blocked mitophagy and oxidative stress accumulation 3. PIAS2 expression correlates with multiple sclerosis severity and disability progression 4. In anaplastic thyroid carcinomas and other aggressive cancers, PIAS2β is dosage-sensitive and required for mitotic spindle assembly; selective depletion triggers mitotic catastrophe while sparing normal cells 5. PIAS2 also promotes melanoma through TRAF2-mediated EPHA5 sumoylation, enhancing receptor stability and signaling 6. Additionally, PIAS2α mediates huANP32A/B sumoylation facilitating avian influenza virus adaptation 7, and PIAS2 dysregulation involves diabetic nephropathy pathogenesis 8. These findings establish PIAS2 as a multifunctional regulator with therapeutic targeting potential in neurodegenerative, autoimmune, and malignant diseases.