PSMG3 (proteasome assembly chaperone 3) is a chaperone protein that promotes assembly of the 20S proteasome core complex, potentially cooperating with PSMG1-PSMG2 heterodimers to orchestrate proper proteasome assembly 1. The protein functions through molecular adaptor activity and protein-binding interactions within the cytosol [GO annotations]. In cancer biology, PSMG3 demonstrates broad oncogenic significance across multiple malignancies. High PSMG3 expression correlates with poor prognosis and is upregulated in most cancer types 1. In hepatocellular carcinoma specifically, PSMG3 overexpression promotes cell proliferation, migration, and invasion capabilities, with involvement in metabolic reprogramming, cell cycle regulation, and PPAR signaling pathways 1. PSMG3 expression associates with tumor mutation burden (TMB), microsatellite instability (MSI), and immune infiltration patterns 1. Beyond cancer, PSMG3 has been identified as a candidate gene for conotruncal heart defects in genome-wide association studies, suggesting developmental roles 2. Additionally, bacterial pathogens exploit PSMG3; the Anaplasma phagocytophilum effector AptA interacts with PSMG3 to enhance host proteasome activity and ubiquitin-proteasome system function, reducing apoptotic efficiency during infection 3. These findings establish PSMG3 as both a fundamental proteasome assembly factor and a multifaceted player in oncogenic progression and pathogenic mechanisms.