Characterization and immunolocalization of RNA polymerase I transcription factor UBF with anti-NOR serum in protozoa, higher plant and vertebrate cells.

We have used anti-NOR serum from a patient with rheumatoid arthritis, to study its reactivity on different phylogenetically separated species such as protozoa, higher plants, birds and mammals. The biochemical characteristics of the antigens detected after applying mono- and two-dimensional electrophoresis and electrophoretic transfers confirm that they correspond to the rRNA polymerase I transcription factor UBF. We have demonstrated the different molecular sizes, depending on the cell complexity, but the same neutral isoelectric points in whole cell extracts of the different species. We have also demonstrated an immunolocalization of this transcription factor to the fibrillar component in all the species studied. These results suggest a high conservation of UBF throughout evolution and the possibility of using this anti-NOR serum as a tool for the study of the structure, nucleolar organization and functional roles of the different nucleolar components.