K. Natarajan et al., YTAF(II)61 HAS A GENERAL ROLE IN RNA-POLYMERASE-II TRANSCRIPTION AND IS REQUIRED BY GCN4P TO RECRUIT THE SAGA COACTIVATOR COMPLEX, MOLECULAR CELL, 2(5), 1998, pp. 683-692
We obtained a recessive insertion mutation in the gene encoding yeast
TBP-associated factor yTAF(II)61/68 that impairs Gcn4p-independent and
Gcn4p-activated HIS3 transcription. This mutation also reduces transc
ription of seven other class II genes, thus indicating a broad role fo
r this yTAF(II) in RNA polymerase II transcription. The Gcn4p activati
on domain interacts with multiple components of the SAGA complex in ce
ll extracts, including the yTAF(II) proteins associated with SAGA, but
not with two yTAF(II)s restricted to TFIID. The taf61-1 mutation impa
irs binding of Gcn4p to SAGA/yTAF(II) subunits but not to components o
f holoenzyme mediator. Our results provide strong evidence that recrui
tment of SAGA, in addition to holoenzyme, is crucial for activation by
Gcn4p in vivo and that yTAF(II)61 plays a key role in this process.