Enhanced transcription by RNA polymerases II and III after inhibition of protein synthesis.

Intraperitoneal administration of cycloheximide (100 mg/kg) to rats produces a time-dependent rise in nuclear RNA polymerase II activity which is maximum at 30 min. This same concentration of cycloheximide also reduces RNA polymerase I activity to 64% of control within this time period. When 10 mg/kg of cycloheximide was administered, there was a 2-fold increase in both RNA polymerases II and III activities within 30 min as assayed in isolated nuclei. When these enzymes are solubilized from nuclei and resolved by DEAE-Sephadex, there is no significant change in the activity of RNA polymerase I or II when assayed on an exogenous template. It is suggested that the dual enhancement of nuclear RNA polymerase II and III activities is the result of a compensatory feedback relationship which exists between translation and transcription in vivo.