Identification and purification of Namalwa nuclear RNP antigen 52/5.3.

Using affinity purified rabbit antibodies to HeLa nucleoli and the Western blotting techniques, an antigen with an approximate molecular weight of 52,000 and pI of 5.3 was found in Namalwa cells (a Burkitt lymphoma), but not in normal liver cells. This antigen was purified from Namalwa RNP by column chromatography on Sephacryl S-200, hydroxylapatite and one-dimensional SDS gel electrophoresis. A liver protein with the same molecular weight and pI value was purified from RNP fraction by one-dimensional SDS gel electrophoresis. Both proteins had similar amino-acid compositions. The tryptic map of 125I-labeled protein 52/5.3 contained approximately nine major spots; spot 9 was present in the Namalwa protein but not in the liver protein. The similarity of the structures of these proteins and their differences in antigenicity are noteworthy and require further structural and functional analysis.