Isolation and analysis of cDNA clones expressing human lupus La antigen.

Abstract

Several c[complementary]DNA clones of the La antigen recognized by certain lupus autoantibodies were isolated from .lambda.gt11 expression libraries made from human liver. Recombinant clones were used to hybrid-select HeLa cell mRNA that was subsequently translated in vitro into a single protein species that comigrated with HeLa cell La protein. The in vitro translated protein was reactive with anti-La patient sera and was identical to the authentic La protein by peptide mapping. By analyzing overlapping cDNA clones, an antigenic site of La protein was mapped at the terminal 12% of the carboxyl end of the molecule. Within this region a unique decapeptide of high hydrophilicity was identified that may constitute a La antigenic determinant. The La antigen expressed from the recombinant clones can be used in a definitive enzyme-linked assay (ELISA) for the classification of sera from patients with systemic lupus erythematosus.