The transcriptional activator Sp1, a novel autoantigen.
OBJECTIVE
To identify one nuclear autoantigenic protein within a complex of DNA binding proteins that bind to GC-rich sequences in Epstein-Barr virus and cellular DNA, and to describe the clinical characteristics of patients whose sera contained autoantibodies to this novel autoantigen.


METHODS
Antibodies to autoantigen Sp1 were initially measured by an electrophoretic mobility shift assay to detect DNA binding proteins. Nuclear extracts and purified Sp1 protein were used in these assays. Recognition of the autoantigen by autoimmune sera was confirmed by immunoprecipitation and immunoblotting.


RESULTS
The autoantigen was identified as Sp1. Anti-Sp1 was detected in sera from 8 (3%) of 230 patients. These sera contained antinuclear antibodies, but lacked antibodies to double-stranded DNA or to several extractable nuclear antigens. The patients whose sera contained antibodies to Sp1 were white women with fatigue, arthritis, Raynaud's phenomenon, malar rash, and photosensitivity.


CONCLUSIONS
Sp1 is the first described example of an RNA polymerase II transcription activator as an autoantigen. The presence of Sp1 autoantibodies is associated with undifferentiated connective tissue disease.
Spain
T A
TA
Yale University School of Medicine, New Haven, Connecticut 06520-8064, USA.
Sun
R
R
Gradzka
M
M
Lin
S F
SF
Craft
J
J
Miller
G
G
D000328:Adult; D000906:Antibodies / Q000097:blood; D000974:Antibodies, Antinuclear / Q000097:blood; D001168:Arthritis / Q000097:blood; D001323:Autoantibodies / Q000097:blood; D001324:Autoantigens / Q000276:immunology*; D004268:DNA-Binding Proteins / Q000276:immunology; D005221:Fatigue / Q000097:blood; D005260:Female; D006801:Humans; D015151:Immunoblotting; D008875:Middle Aged; D011233:Precipitin Tests; D011928:Raynaud Disease / Q000097:blood; D012091:Repetitive Sequences, Nucleic Acid / Q000276:immunology; D016329:Sp1 Transcription Factor / Q000276:immunology*
D000906:Antibodies; D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D001324:Autoantigens; D004268:DNA-Binding Proteins; D016329:Sp1 Transcription Factor