THE PUTATIVE ONCOPROTEIN DEK, PART OF A CHIMERA PROTEIN ASSOCIATED WITH ACUTE MYELOID-LEUKEMIA, IS AN AUTOANTIGEN IN JUVENILE RHEUMATOID-ARTHRITIS

The 45-kD autoantigen associated with juvenile rheumatoid arthritis (J RA) has been isolated from HeLa cell nuclei and purified about 2500-fo ld to near homogeneity in a five-step chromatographic procedure. Purif ication of the antigen was monitored by immunoblot assays using a near ly monospecific anti-45-kD serum from a child with JRA. Tryptic peptid e mapping and partial amino acid sequencing of the purified 45-kD anti gen demonstrated its identity with the DEK protein. DEK is a 43-kD pro tein of unknown function expressed by the putative oncogene dek locate d on chromosome 6. As a result of a (6;9) translocation associated wit h a rare subtype of acute myeloid leukaemia a chimeric protein contain ing most of DEK amino acids at the N-terminus is found in leukaemic ce lls (von Linden et al., Mol Cell Biol. 1992; 12: 1687-97). The 43-kD D EK was detected by immunoblotting with serum from a patient with JRA i n a variety of rat tissues, and was most abundant in the spleen and in bone marrow.