Sera from human patients with
systemic lupus erythematosus (SLE) have been shown to react with
snRNP particles of both mammals and Drosophila (Mount, S. M. and J. A. Steitz. 1981.
Nucleic Acids Res. 9:6351-6368). We have utilized fully characterized monospecific sera and specifically purified
antibodies to carry out indirect immunofluorescence experiments with frozen sections of Drosophila embryos. Embryos subjected to severe heat shock before sectioning showed reduced binding of anti-Sm sera. Anti-nRNP sera reacted identically with
antigens of heat shocked and non-heat-shocked sections. The reduction in anti-Sm fluorescence was restored by a brief
salt wash. These results imply a noncovalent alteration in the conformation of Sm
antigens with the administration of heat shock that can revert with exposure to
salt. Drosophila
antigens have been compared to mammalian standards, showing partial identity with bovine spleen extract (BSE)
antigens when reacted with anti-Sm sera. The antigenic relatedness between affinity-purified heat-shocked and non-heat-shocked Drosophila
antigens and their mammalian homologues was examined by quantitative ELISA methodology. In all cases, the Drosophila
antigens from heat-shocked and non-heat-shocked embryos were identical. We theorize that the heat shock-induced alteration of Sm
antigen reverst during extraction. Because the
snRNP antigens have been shown to be involved in splicing, and because splicing is inhibited during heat shock (Yost, H. J., and S. Lindquist. 1986. Cell. 45:185-193), our results provide information on the nature and stability of a change in these
antigens which may be a central
element in control of the heat shock response.