Expression of the yeast HO gene in late G(1) of the cell cycle requires the
SWI/SNF chromatin remodeling complex, the Gcn5p histone acetyltransferase,
and two different sequence-specific transcriptional activators, Swi5p and
Swi4p/Swi6p. We have used chromatin immunoprecipitation assays to investiga
te the role of each of these trans-acting factors in establishing a cell cy
cle-regulated domain of histone acetylation surrounding the HO upstream reg
ulatory region. We detect a similar to 1-kb domain of H3 and H4 acetylation
that is established in mid-G(1), prior to and independent of HO transcript
ion, which then declines with kinetics similar to inactivation of HO. This
cell cycle burst of histone acetylation requires Gcn5p, SWI/SNF, and the Sw
i5p activator, but occurs in the absence of the Swi4p activator. We also fi
nd that inactivation of the Sin3p/Rpd3p deacetylase complex leads to a high
level of acetylation at the HO locus throughout the cell cycle. We propose
a sequential model for activation of HO in which the Swi5p-dependent recru
itment of the Gcn5p acetyltransferase requires chromatin remodeling events
by the SWI/SNF complex.