Interplay between promoter occupancy and chromatin remodeling requirements in transactivation of the S.cerevisiae PHO5 gene

In higher eukaryotes, DNA is packaged with histones and other proteins into chromatin. While this is important in the control of unwanted gene expression, chromatin also serves as a barrier to many vital functions in the cell. Therefore, cells have evolved many different types of chromatin remodeling enzymes to contend with this inhibitory structure and enable gene expression and other functions. The Saccharomyces cerevisiae PHO5 gene is triggered in response to phosphate starvation. In this study, I evaluate the chromatin remodeling requirements of this gene with respect to the multisubunit complexes SWI/SNF and SAGA. I show, for the first time, physical recruitment of SWI/SNF to the PHO5 promoter. I also demonstrate the role of promoter occupancy in influencing requirements for chromatin remodeling enzymes. Further, I describe various interactions between these two complexes at the PHO5 promoter. This study presents evidence for the first instance of excess recruitment of an ATP-dependent remodeler potentially compensating for the lack of a histone acetyltransferase.