DDX3X and rheumatoid arthritis: RNF39 was located in the MHC-I region.[26] Studies have suggested that a large number of immune-related genes were in MHC-I region, such as rheumatoid arthritis and systemic lupus erythematosus.[27,28]RNF39 mediated polyubiquitination of k48 junctions and promoted the proteasome degradation of DEAD-box RNA helicase DDX3, an important scaffold of mitochondrial antiviral signaling protein/tumor necrosis factor receptor-associated factor 3 complex formation.[29] New evidence suggested that RNF39 was a potential immunomodulator.