PROJECT SUMMARY The evolutionarily conserved SWI/SNF chromatin remodeler, exists as distinct polymorphic complexes, BAF, PBAF and ncBAF, each with differing subunit composition. Though these complexes share a common biological function of altering chromatin architecture, it is the unique subunits within each form of SWI/SNF that help define their genomic roles. With the identification of SWI/SNF as a tumor suppressor, a lot of attention has been focused on how loss of subunits leverage the remaining complexes for transcriptional output. However, focusing attention on a normal cell that needs to constantly adjust transcriptional output to respond to a variety of external stimuli, an interesting question remains: How do cells dynamically alter the usage of the various SWI/SNF complexes for gene expression and do they achieve this dynamic usage by changing the amounts of each form of the complex within cells. We have leveraged hypoxia as an environmental stimulus to address this very question. Our preliminary studies show that hypoxic cells retain BAF and ncBAF proteins at levels similar to those in normoxic cells, but decrease levels of PBAF members, while displaying a dependence on BAF for expression of hypoxic genes. The overall goal of this proposal is to gain mechanistic understanding of the dynamic regulation and usage of various forms of SWI/SNF as a response to environmental cues, specifically hypoxic exposure. In AIM 1, we will define the composition of the various forms of SWI/SNF, during hypoxic response, with emphasis on how varying levels of oxygen concentration affects SWI/SNF complex levels, using both 2D and 3D cell culture models. In AIM 2, we ask how cells use the altered stoichiometry of SWI/SNF forms for regulation of hypoxic gene expression. In AIM 3, we seek to define the molecular mechanisms of downregulation of PBAF during hypoxia. Our studies, will cumulatively provide a mechanistic understanding of how cells dynamically utilize the various forms of SWI/SNF to respond to changing environmental signals. Given that many chromatin modifiers exist in a plurality of forms, our studies will help identify mechanisms that may commonly be in play to regulate functions and usage of these important enzyme complexes.

PROJECT NARRATIVE SWI/SNF plays critical roles in many cellular processes, from response to environmental stress, to differentiation and development. However, mis-regulation of this complex causes cancers. The goal of this proposal is to understand how environmental stress, specifically hypoxia which is present in tumors, mediates changes in compositional variation of SWI/SNF and uses different forms of SWI/SNF for gene expression during hypoxia. Given loss of SWI/SNF units result in many cancers that form solid tumors with hypoxic centers, our studies will help understand the underlying mechanisms of how SWI/SNF functions as a tumor suppressor.