THE HUMAN CAN PROTEIN, A PUTATIVE ONCOGENE PRODUCT ASSOCIATED WITH MYELOID LEUKEMOGENESIS, IS A NUCLEAR-PORE COMPLEX PROTEIN THAT FACES THECYTOPLASM

We have carried out partial amino acid sequence analysis of a putative nuclear pore complex protein (nucleoporin) of rat that reacts with wh eat germ agglutinin and with the polyspecific monoclonal antibody 414. Surprisingly, these partial amino acid sequence data revealed a high degree of similarity with the human CAN protein, the complete cDNA-der ived primary structure of which was reported by Von Lindern et al. [Vo n Lindern, M., Fornerod, M., van Baal, S., Jaegle, M., de Wit, T., Bui js, A. & Grosveld, G. (1992) Mol. Cell. Biol. 12, 1687-1697]. The CAN protein has been proposed to be a putative oncogene product associated with myeloid leukemogenesis. Its subcellular localization was not est ablished. To confirm that the putative rat nucleoporin is indeed a hom olog of the human CAN protein and to determine its subcellular localiz ation, we expressed a 39-kDa internal segment of the 213,790-Da human CAN protein in Escherichia coli and raised monospecific antibodies, wh ich reacted with the putative rat nucleoporin. Immunofluorescence micr oscopy of HeLa cells gave a punctate nuclear surface staining pattern characteristic of nucleoporins, and immunoelectron microscopy yielded specific decoration of the cytoplasmic side of the nuclear pore comple x. This suggests that the protein is part of the short fibers that ema nate from the cytoplasmic aspect of the nuclear pore complex. In agree ment with previously proposed nomenclature for nucleoporins, we propos e the alternative term nup214 (nucleoporin of 214 kDa) for the CAN pro tein.