Target antigens of the SSA/Ro and SSB/La system.
The SSA/Ro and SSB/La antigens are polypeptides which serve as autoantigens in systemic lupus erythematosus and Sjogren's syndrome. The SSA/Ro contains two major isoforms of 60 kD and 52 kD. The former is the main native antigen while the latter is a major autoantigen in its denatured form. The SSB/La is a single phosphorylated protein of 48 kD. Recently a new protein of 46 kD, termed calregulin, was suggested as an additional component of the SSA/Ro antigens. However, extensive investigations failed to confirm its relation to the SSA/Ro system. Based on molecular techniques and cDNA cloning of these antigens, it was demonstrated that the 60 kD protein is capable of binding RNA and DNA molecules, suggesting a regulatory role in transcription for this antigen. The 52 kD polypeptide contains multiple zinc finger motifs and its sequence is homologous to the mouse rptl protein, which is a T-cell regulating peptide. The SSB/La is associated with precursors of 5S RNA and tRNA, implying that it has a role in the synthesis and maturation of RNA polymerase III transcripts. The 60 kD and 52 kD SSA/Ro components may be associated within the cell. The SSA/Ro and SSB/La may also be in complex in some points of the cell cycle.
Ben-Chetrit
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Department of Internal Medicine, Hadassah University Hospital, Jerusalem, Israel.
D000328:Adult; D000818:Animals; D000974:Antibodies, Antinuclear / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology* / Q000302:isolation & purification / Q000502:physiology; D001327:Autoimmune Diseases / Q000276:immunology*; D003429:Cross Reactions; D005260:Female; D006327:Heart Block / Q000151:congenital / Q000209:etiology / Q000276:immunology; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011248:Pregnancy Complications / Q000276:immunology; D020733:RNA, Small Cytoplasmic; D011817:Rabbits; D012261:Ribonucleoproteins / Q000276:immunology* / Q000302:isolation & purification / Q000502:physiology; D012859:Sjogren's Syndrome / Q000276:immunology*; D000097585:SS-B Antigen; D000099207:SS-A Antigen
D000974:Antibodies, Antinuclear; D001324:Autoantigens; D020733:RNA, Small Cytoplasmic; D012261:Ribonucleoproteins; D000097585:SS-B Antigen; D000099207:SS-A Antigen; C116006:RO60 protein, human; C035356:SS-A antibodies; C035357:SS-B antibodies