Ubiquitination of Ro52 autoantigen.
Anti-Ro/SSA antibodies are antinuclear antibodies most commonly found in patients with Sjögren's syndrome, a chronic autoimmune disease characterized by dryness of the eyes and mouth. The autoantibodies recognize a RING-finger protein, Ro52/SSA (52 kDa), whose function is still unknown. In this study, the ubiquitination of Ro52 was investigated. We found that Ro52 was strongly conjugated by a single molecule of ubiquitin in cells. Although the biological relevance of this mono-ubiquitination was not defined, the function of Ro52 might be modified by the mono-ubiquitination. We also found that Ro52 was conjugated with poly-ubiquitin chain in cells (poly-ubiquitination), suggesting that Ro52 may be downregulated by the ubiquitin-proteasome pathway in vivo. Interestingly, sera from patients with Sjögren's syndrome showed heterogeneity in their reactivity to poly-ubiquitinated Ro52, probably because of their differing antigenic determinants. This heterogeneity of the reactivity might be associated with the varying clinical features found in patients with Sjögren's syndrome.
Fukuda-Kamitani
Taeko
T
Department of Internal Medicine, The University of Texas-Houston Health Science Center, Houston, TX 77030, USA.
Kamitani
Tetsu
T
D000818:Animals; D001324:Autoantigens / Q000276:immunology* / Q000378:metabolism*; D015153:Blotting, Western; D019556:COS Cells; D003035:Cobalt / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D015723:Gene Library; D006801:Humans; D051379:Mice; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins / Q000276:immunology* / Q000378:metabolism*; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism*; D000099207:SS-A Antigen
D001324:Autoantigens; D003035:Cobalt; D018076:DNA, Complementary; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D025801:Ubiquitin; D000099207:SS-A Antigen; C116006:RO60 protein, human