Immunological studies on plant DNA-dependent RNA polymerases with antibodies raised against individual subunits

Antibodies were raised against native soybean RNA polymerase II and individual subunits of RNA polymerase II purified from soybean, cauliflower, and wheat. These antibodies were used to study the immunological relationships of plant RNA polymerases I, II, and III at the subunit level. RNA polymerases I and II from soybean, I, II, and III from cauliflower and wheat, and II from turnip were purified to homogeneity, and enzyme subunits were separated on polyacrylamide gels containing sodium dodecyl sulfate. Separated RNA polymerase subunits were electrophoretically transferred to nitrocellulose, reacted with antibodies, and the immunoglobulin complexes were revealed by reaction with 125I-labeled Protein A. Antibodies directed against native soybean RNA polymerase II bind to all or most of the subunits of soybean and wheat RNA polymerase II and to the putative common subunits in RNA polymerases I and III. Antibodies directed against individual subunits of RNA polymerase II enzymes react specifically with the subunit to which the antibody was raised and to related or identical subunits in RNA polymerases I and III. These studies confirm the presence of common subunits in the three classes of nuclear RNA polymerase and provide information on analogous or related subunits within each class of enzyme purified from different plant species.