DCUN1D4 encodes an E3 ubiquitin ligase component that functions as a NEDD8-conjugating enzyme transferring NEDD8 to cullin proteins, activating cullin-RING E3 ubiquitin ligases (CRLs) essential for targeted protein degradation. The gene is expressed across diverse tissues and cell types, with expression changes documented in platelets during storage 1 and serum exosomes in menopausal women with osteoporosis 2. Beyond its canonical role in neddylation, DCUN1D4-derived circular RNA (circDCUN1D4) exhibits tumor-suppressive functions in lung adenocarcinoma by stabilizing thioredoxin-interacting protein (TXNIP) mRNA through interaction with RNA-binding protein HuR, thereby suppressing metastasis and glycolysis 3. Clinically, circDCUN1D4 downregulation correlates with lymph node metastasis and poor overall survival in lung adenocarcinoma patients 3. The gene's dysregulation appears relevant to multiple pathologies: its expression changes associate with platelet storage lesion in transfusion medicine 1, it emerges as a hub gene in osteoporosis-associated regulatory networks 2, and its circular RNA isoform functions as an independent prognostic marker in lung cancer. These findings suggest DCUN1D4 possesses both conventional protein neddylation functions and unconventional regulatory roles through circular RNA mechanisms.