We have previously described a novel complex of
proteins which contains the U1snRNP-A
protein (U1A) but no other
small nuclear ribonucleoprotein particle (
snRNP) components (O'Connor et al.,
RNA 1997;3:1444-55).
Antibodies to this novel complex inhibit both splicing and polyadenylation in vitro of a test
pre-mRNA (O'Connor et al.,
RNA 1997;3:1444-55; Lutz et al.,
RNA 1998;4:1493-9). This novel complex of
proteins was identified using an unusual mouse
monoclonal antibody (MoAb), called MAb 12E12. We were interested to know if autoimmune patient sera were similar to this MoAb. We have discovered a novel specificity of
systemic lupus erythematosus patient sera reminiscent of MAb 12E12 in that the patient serum, like 12E12, (1) does not recognize U1A when bound to
U1 RNA, (2) recognizes primarily the
epitopes in the amino-terminal third of the
protein, including RNA recognition motif 1 (RRM1) and (3) inhibits in vitro polyadenylation. These findings may lead to the discovery of previously undescribed
autoantigens as components of the novel
protein complex, and may provide insight into
autoimmune diseases.