Anti-U1A monoclonal antibodies recognize unique epitope targets of U1A which are involved in the binding of U1 RNA.
The U1A (or nRNP A) protein is known to play a critical role in eukaryotic pre-mRNA splicing and polyadenylation. Previous studies revealed that several mouse monoclonal antibodies (MAbs) recognized U1A as part of the U1snRNP, while MAb 12E12 was unique in that it recognized an epitope that is masked when U1A is bound to U1 RNA. In order to further characterize and understand the antigenic targets of these MAbs, we undertook fine specificity epitope mapping studies. Anti-U1A MAbs 12E12 and 10E3 each recognize unique peptides from the U1A protein. Interestingly, these MAbs recognize epitopes which have been shown to be antigenic in human autoimmune diseases. When superimposed on structures of U1A derived from crystal and NMR data, the major epitope recognized by 12E12 (amino acids 103-108) localizes to the surface of the U1A molecule. The 12E12 epitope is immediately adjacent to a helix which probably reacts to U1 RNA binding by undergoing a conformational change. This modification of structure effectively masks the 12E12 epitope, thus preventing binding of the monoclonal to U1A/U1 RNA complexes. These findings suggest that the structure of the U1A protein may be different when not part of the U1snRNP.
Department of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical School, Newark, NJ 07103, USA. lutzcs@umdnj.edu
Carol S
CS
Lutz
Micah T
MT
McClain
John B
JB
Harley
Judith A
JA
James
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D001665:Binding Sites; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000737:chemistry / Q000276:immunology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D012342:RNA, Small Nuclear / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000276:immunology* / Q000378:metabolism*; D012680:Sensitivity and Specificity; D020349:Surface Plasmon Resonance
D000911:Antibodies, Monoclonal; D000939:Epitopes; D012342:RNA, Small Nuclear; D016601:RNA-Binding Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; C405483:U1 small nuclear RNA; C075339:U1A protein