Activated transcription independent of the RNA polymerase II holoenzyme in budding yeast

We investigated whether the multisubunit holoenzyme complex of RNA polymerase II (Pol IH) and mediator is universally required for transcription in budding yeast. Delta CTD Pol II lacking the carboxy-terminal domain of the large subunit cannot assemble with mediator but can still transcribe the CUP1 gene. CUP1 transcripts made by Delta CTD Pol II initiated correctly and some extended past I-he normal poly(A) site yielding a novel dicistronic mRNA. Most CUP1 transcripts made by Delta CTD Pol LH were degraded but could be stabilized by deletion of the,XRN1 gene. Unlike other genes, transcription of CUP1 and HSP82 also persisted after inactivation of the CTD kinase Kin28 or the mediator subunit Srb4. The upstream-activating sequence (UAS) of the CUP1 promoter was sufficient to drive Cu2+ inducible transcription without Srb4, and heat shock inducible transcription without the CTD. We conclude that the Pol LI holoenzyme is not essential far all UAS-dependent activated transcription in yeast.