PA2G4 (proliferation-associated 2G4), also known as ErbB3-binding protein 1, is a multifunctional regulator involved in transcription, translation, and ribosome biogenesis. It acts as a corepressor of the androgen receptor and inhibits E2F1-regulated transcription, while also binding RNA and associating with ribosomal components to regulate intermediate and late steps of rRNA processing. The protein exists as two isoforms with opposing functions: PA2G4-p42 suppresses apoptosis, whereas PA2G4-p48 promotes cell differentiation 1. PA2G4 additionally mediates cap-independent translation of picornaviral IRESs 2, positioning it as a host factor for viral replication. PA2G4 plays a dual, context-dependent role in cancer. Expression levels correlate with prognosis across neuroblastoma, cervical, brain, breast, prostate, pancreatic, and hepatocellular tumors 3. In nasopharyngeal carcinoma, elevated PA2G4 expression associates with tumor size, lymph node metastasis, and poor overall survival 4. PA2G4 functions as an oncogenic cofactor by stabilizing MYCN protein in neuroblastoma through direct binding, enabling a novel therapeutic strategy: small-molecule inhibitors of the PA2G4-MYCN interface (WS6 analogues) show anti-tumor activity with reduced toxicity to normal cells 5 6. In 3q26 AML, PA2G4 overexpression rescues cells from histone deacetylase inhibitors, and genetic or pharmacologic PA2G4 inhibition abrogates EVI1-driven leukemogenesis 7. Recent evidence suggests PA2G4 potentiates amyloid-β pathology in Alzheimer's disease by inhibiting γ-secretase; forebrain-specific deletion produces AD-like phenotypes, and AAV-delivered PA2G4 reduces amyloid burden in disease models 8.