title: Anti-RNA polymerase I antibodies in the sera of MRL lupus mice at the initial stages of disease are directed primarily against phosphorylation-dependent epitopes.
abstract: Anti-RNA polymerase I (RPI) antibodies in the sera of MRL/Mp-lpr/lpr and MRL/Mp(-)+/+ mice, which develop an autoimmune disease similar to human systemic lupus erythematosus, were screened for reactivity with purified RPI or RPI which had been dephosphorylated. In every case (n = 10), dephosphorylation of RPI resulted in a significant decrease (33-95%) in antibody binding. The anti-RPI antibodies in the sera of the same mice approximately 6 weeks later also reacted better with untreated as compared to dephosphorylated RPI but, in every case, the decrease in antibody (0-30%) caused by dephosphorylation was substantially diminished. That the proportion of anti-RPI antibodies in the sera of MRL mice decreased with progression of lupus-like disease was confirmed by closely monitoring the antibodies over the course of disease. Anti-RPI antibodies produced at the earliest stages appeared to be directed almost exclusively against phosphorylation-dependent determinants since dephosphorylation of RPI essentially abolished antibody binding. Subsequently, the percentage of the total anti-RPI antibodies in the sera of these mice directed towards phosphorylation-independent epitopes increased linearly with time. The importance of phosphorylation-dependent epitopes on RPI for the development of the anti-RPI autoimmune response was supported by the observation that treatment of mice with alkaline phosphatase partially attenuated anti-RPI antibody production.
authors.affiliation: Department of Biochemistry, University of Kansas, Lawrence 66045.
authors.forename: D A
authors.initials: DA
authors.lastname: Stetler
authors.forename: D
authors.initials: D
authors.lastname: Signorelli
authors.forename: J
authors.initials: J
authors.lastname: Neil
authors.forename: S
authors.initials: S
authors.lastname: Brady
authors.forename: R
authors.initials: R
authors.lastname: Engler
authors.forename: J C
authors.initials: JC
authors.lastname: Brown
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000032:analysis*; D015551:Autoimmunity; D000939:Epitopes; D007668:Kidney / Q000276:immunology; D008180:Lupus Erythematosus, Systemic / Q000276:immunology*; D051379:Mice; D010766:Phosphorylation; D012318:RNA Polymerase I / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D012318:RNA Polymerase I