| Chromatin structure is inhibitory to the binding of DNA factors necessary for gene regulation. The basic subunit of chromatin is the nucleosome, composed of 146bp of generally inaccessible DNA wrapped around a histone octamer. ATP-dependent chromatin remodelers utilize the energy of ATP hydrolysis to alter nucleosome positions and structure. The numerous remodeler subfamilies have distinct functions associated with their activity including chromatin assembly, DNA replication, repair, and transcription. Although remodelers have been implicated in various cellular processes, the roles of specific remodeling products in gene regulation are not fully understood. This thesis discusses insights into mechanisms of gene regulation by ATP-chromatin remodeling through two approaches. The first approach examines sequence specific remodeling of in vitro polynucleosomal templates by hSWI/SNF and SNF2h remodeling complexes. We find that remodelers tend to move nucleosomes away from strong nucleosome positioning sequences. The second approach focuses on hSWI/SNF remodeling targeted by Glucocorticoid Receptor activation. Through high-resolution nucleosome position mapping on custom tiling microarrays, we observe a temporary increase of nucleosomes on induced and repressed genes that is dependent upon hSWI/SNF activity. This effect is in the context of specific positioning of nucleosomes that may expose or occlude regulatory sequences. Taken together, these studies shed new light on the determinants and functions of remodeling products in gene regulation, and establish techniques for examining specific changes in chromatin architecture in response to cellular signals. |
