yTAFII61 has a general role in RNA polymerase II transcription and is required by Gcn4p to recruit the SAGA coactivator complex.

We obtained a recessive insertion mutation in the gene encoding yeast TBP-associated factor yTAFII61/68 that impairs Gcn4p-independent and Gcn4p-activated HIS3 transcription. This mutation also reduces transcription of seven other class II genes, thus indicating a broad role for this yTAFII in RNA polymerase II transcription. The Gcn4p activation domain interacts with multiple components of the SAGA complex in cell extracts, including the yTAFII proteins associated with SAGA, but not with two yTAFIIs restricted to TFIID. The taf61-1 mutation impairs binding of Gcn4p to SAGA/yTAFII subunits but not to components of holoenzyme mediator. Our results provide strong evidence that recruitment of SAGA, in addition to holoenzyme, is crucial for activation by Gcn4p in vivo and that yTAFII61 plays a key role in this process.