PSME3 and systemic lupus erythematosus: RPA32 co-migrates with the U1snRNPs-A protein (U1-A, immunoprecipitated by anti-nRNP and anti-Sm antibodies), that can be found in about 40% of SLE sera [5], and Ki (SL) antigen, which is recognized by about 10% of SLE sera [24,25].