Frequent occurrence of anti-tRNA(His) autoantibodies that recognize a conformational epitope in sera of patients with myositis.
OBJECTIVE
To investigate the incidence of autoantibodies directed to deproteinized transfer RNA(His) (tRNA(His)) in anti-Jo-1 positive myositis patients and to determine the major B cell epitope.


METHODS
One hundred sixty-seven myositis sera were screened by immunoblotting and enzyme-linked immunosorbent assay for the presence of anti-Jo-1 antibody. Autoantibodies directed to deproteinized RNA were detected by immunoprecipitation. Ribonuclease cleavage experiments were performed to determine the tRNA(His)-specific features important for recognition.


RESULTS
Approximately one-third of the anti-Jo-1 positive sera also contained autoantibodies recognizing tRNA(His). This recognition was independent of modified bases, but the presence of stabilizing Mg2+ ions appeared to be essential for efficient immunoprecipitation. Transfer RNA(His)-specific features in the anticodon loop were not protected from ribonuclease cleavage by bound antibodies, while protection of bases located in the D and T loops was observed.


CONCLUSIONS
A significant number of anti-Jo-1 positive myositis sera contain anti-tRNA(His) activity. Formation of the major autoepitope on tRNA(His) is strongly dependent on proper folding of this molecule mediated by an interaction between D and T loops which is stabilized by either modified residues or Mg2+ ions.
University of Nijmegen, The Netherlands.
R
R
Brouwer
W
W
Vree Egberts
P H
PH
Jongen
B G
BG
van Engelen
W J
WJ
van Venrooij
D001323:Autoantibodies / Q000276:immunology*; D003429:Cross Reactions; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D006643:Histidine-tRNA Ligase / Q000032:analysis*; D006801:Humans; D008968:Molecular Conformation; D009220:Myositis / Q000235:genetics / Q000276:immunology*; D010446:Peptide Fragments / Q000276:immunology; D011233:Precipitin Tests; D012313:RNA / Q000276:immunology; D012354:RNA, Transfer, His / Q000235:genetics* / Q000276:immunology*
D001323:Autoantibodies; D000939:Epitopes; D010446:Peptide Fragments; D012354:RNA, Transfer, His; D012313:RNA; D006643:Histidine-tRNA Ligase