20-HYDROXYECDYSONE STIMULATES RNA-POLYMERASE-I ACTIVITY IN SILKMOTH WING EPIDERMIS BY INCREASED SYNTHESIS AND PHOSPHORYLATION

The activities of RNA polymerases I and II in the wing epidermis of di apausing silkmoth pupae increased about tenfold during the first day a fter administration of either 20-hydroxyecdysone (20E) or 20E plus juv enile hormone (Katula et al., 1981a). The aim of these studies was to correlate these increases in RNA polymerase I and II activities to the ir amounts in hormone stimulated wing epidermis. The enzyme activities were measured by standard procedures while their amounts were determi ned by the application of a modified ELISA with subunit-specific monoc lonal antibodies. Results showed that the increase in the amount of RN A polymerase I during the first 24 h accounted for only about 60% of t he increase in activity. Alkaline phosphatase decreased the activity o f the newly synthesized enzyme by 40-50%. These results indicate that hormone-stimulation of RNA polymerase I activity is due to a combinati on of synthesis of the enzyme and phosphorylation of the enzyme and/or tightly associated factors. RNA polymerases II and III determined by differential ELISA using a monoclonal antibody specific to a common su bunit followed developmental changes similar to those of RNA polymeras e I. The amounts and activity of the enzymes during the first 48 h wer e similar in wing tissue that followed the second pupal development (2 0E + juvenile hormone) compared to tissue that developed into adult wi ngs (20E).