Unconventional Prefoldin RPB5 Interactor (URI)

NNX3 lacks a signal peptide and a transmembrane domain. Western blot analysis showed expression of an approximately 65-kD protein, higher than the predicted 50 kD. Immunofluorescence microscopy demonstrated predominantly cytoplasmic expression. Northern blot analysis revealed wide expression of a 2.6-kb transcript that was most abundant in skeletal muscle. Immunohistochemical analysis indicated strong expression in mouse embryonic brain and neuronal tissue, as well as expression in numerous other tissues paralleling expression observed in human autopsy specimens. Expression was also detected in small cell lung carcinoma cells and Reed-Sternberg cells of Hodgkin disease, although expression was not found in all tumor cell lines.