RNA polymerase II degradation in response to rapamycin is not mediated through ubiquitylation

► RNAPII is degraded in response to rapamycin requiring the Tor1 signaling pathway. ► The peptidyl prolyl isomerase Rrd1 is required for this process. ► Degradation of RNAPII is independent of its ubiquitylation. ► Rrd1 mediates the degradation through a novel mechanism.