Immunological relatedness of subunits of RNA polymerase II from insects and mammals.

A procedure is described which allows rapid purification of RNA polymerase II from either embryos of Drosophila melanogaster or larvae of Chironomus thummi. The polypeptide compositions of the enzymes were compared in denaturing gels. Antisera were raised against the native enzymes and were tested for binding activity to separated subunits of each enzyme. Sheep antibodies to Drosophila RNA polymerase were found to react with most polypeptides of the insect RNA polymerases but only with the high-molecular weight subunits of calf thymus RNA polymerase II. These were also found to cross-react with a monoclonal antibody directed against the large subunits of the Drosophila enzyme. An antiserum to Chironomus RNA polymerase II reacted with the three largest subunits of this enzyme and subunits 0, 1 and 2 of Drosophila RNA polymerase II. The purified IgG fractions of the polyspecific antisera inhibited the activity in vitro of the insect RNA polymerases to different degrees.