The DNA binding domains of UBF represent major human autoepitopes conserved in vertebrates species.

A human autoantigen (NOR-90) previously shown to be the upstream binding factor UBF, binds to the ribosomal RNA genes clustered at the nucleolus organizer regions (NORs). Truncated recombinant forms of hamster UBF were expressed in E. coli and it served to demonstrate that the DNA binding domains of UBF are major autoepitopes as shown by immunoblots analyses with a human autoimmune anti-NOR serum. Several monospecific antibodies to those recombinant truncated UBF polypeptides were generated as shown by immunofluorescence (IF) and Western blots. Immunoblots and IF studies using these anti-UBF sera in cell cultures of various vertebrates species from fish to mammals, indicate the conservation of the DNA binding domains of the ribosomal transcription factor during evolution.