L. Kuras et K. Struhl, Binding of TBP to promoters in vivo is stimulated by activators and requires Pol II holoenzyme, NATURE, 399(6736), 1999, pp. 609-613
In eukaryotes, transcriptional activators have been proposed to function by
recruiting the RNA polymerase II (Pol II) machinery(1-3), by altering the
conformation of this machinery(4,5), or by affecting steps after initiation
(6-8), but the evidence is not definitive. Genomic footprinting of yeast TA
TA-box elements reveals activator-dependent alterations of chromatin struct
ure(9) and activator-independent protection(10), but little is known about
the association of specific components of the Pol II machinery with promote
rs in vivo. Here we analyse TATA-box-binding-protein (TBP) occupancy of 30
yeast promoters in vivo. We find that TBP association with promoters is sti
mulated by activators and inhibited by the Cyc8-Tup1 repressor, and that tr
anscriptional activity correlates strongly with the degree of TBP occupancy
. In a small subset of promoters, TBP occupancy is higher than expected whe
n gene activity is low, and the activator-dependent increase is modest. TBP
association depends on the Pol II holoenzyme component Srb4, but not on th
e Kin28 subunit of the transcription factor TFIIH, even though both protein
s are generally required for transcription. Thus in yeast cells, TBP associ
ation with promoters occurs in concert with the Pol II holoenzyme, activato
r-dependent recruitment of the Pol II machinery occurs at the vast majority
of promoters, and Kin28 acts after the initial recruitment.