Antibodies to yeast Sm motif 1 cross-react with human Sm core polypeptides

Two regions common to all UsnRNP core polypeptides have been described: Sm motif 1 and Sm motif 2. Rabbits were immunized with a 22 amino-acid peptide containing one segment of Sm motif 1 (YRGTLVSTDNYFNLQL-NEAEEF, correspondi ng to residues 11-32) from yeast F protein. After immunization, the rabbit sera contained antibodies that not only reacted specifically with the pepti de from yeast F protein but also cross-reacted with Sm polypeptides from ma mmals; that is, with purified human U1snRNPs. The results suggest that the peptide used and human Sm polypeptides contain a common feature recognized by the polyclonal antibodies. A large collection of human systemic lupus er ythematosus sera was assayed using the yeast peptide as an antigen source. Seventy per cent of systemic lupus erythematosus sera contain an antibody s pecificity that cross-reacts with the yeast peptide.