PROJECT SUMMARY
Dynamic changes to chromatin structure are essential for regulating gene expression in cells. These changes
are mediated by chromatin-associated factors such as histone modifiers, chaperones, and chromatin
remodelers. Mutations in these factors are strongly linked to many human diseases. For example, mutations
in the conserved SWI/SNF family of ATP-dependent chromatin remodelers are linked to ~20% of human
cancers. Some of these mutations are also linked to developmental and intellectual disability syndrome, such
as Coffin-Siris syndrome (CSS). However, we do not fully understand what aspects of SWI/SNF remodeling
activities are affected by the disease-causing mutations under physiological conditions. The Remodels the
Structure of Chromatin (RSC) complex is a member of the SWI/SNF family, and is the only essential
remodeler in budding yeast. RSC regulates many biological processes, including transcription by all three
RNA polymerases. It is critically involved in maintaining canonical chromatin structure near gene-promoters.
Many domains have been identified within the RSC ATPase subunit Sth1 that modulate its remodeling activity.
Additional domains are implicated in interacting with DNA and nucleosomes. However, the contributions of
these domains in dictating RSC function in living cells are poorly understood. Furthermore, the mechanisms
that regulate the association of RSC with chromatin are also not clear. RSC could bind to specific regions of
chromatin using its bromodomains that have been shown to bind acetylated histones in vitro. How RSC
exploits histone acetylation for its recruitment or to execute its function under physiological conditions remains
to be understood. Using Saccharomyces cerevisiae as a model organism, in the specific AIM 1), we will
investigate the impact of mutations in various regulatory and nucleosome-binding domains, and some of the
mutations that are linked to developmental abnormalities on chromatin structure, including accessibility and
gene expression. We will examine how mutations in these important domains affect the ability of cells to
respond to stress. In the specific AIM 2), we will identify the histone tail residues that promote RSC association
with chromatin and those that help RSC disengage from chromatin. The extent to which acetylated residues
affect RSC ability to make DNA accessible will also be determined, genome-wide. Furthermore, we will
examine the role of RSC in regulating transcription during elongation steps. These studies will be valuable in
understanding how histone modifiers and chromatin remodelers cooperate to regulate gene expression.