Abstract 1972: Changes in the architecture, interactions and chromatin remodeling of SWI/SNF due to loss of Snf5

Abstract The mammalian SWI/SNF complex is a family of an estimated ∼100 complexes, each with different combinations of related subunits. Efforts in sequencing many cancer genomes has revealed that mammalian SWI/SNF complexes is one of the most frequently mutated epigenetic factors found in a broad range of cancers. In order to understand more about the subunit organization of SWI/SNF and because yeast and mammalian SWI/SNF complexes share many conserved subunits and domains; we have studied the role of the Snf5 subunit in the yeast SWI/SNF to better understand the role of the mammalian homolog SNF5 that is a known tumor suppressor gene. The basis for the loss of mammalian SNF5 being a driver mutation in pediatric rhabdoid tumors is currently not well understood or how the loss of SNF5 effects the composition, recruitment and nucleosome remodeling activity of the SWI/SNF complex. We have assessed the effects on deletion of Snf5 on the compositional integrity of SWI/SNF and have evidence for Snf5 forming a sub-complex with two other highly conserved subunits of SWI/SNF that are lost from the complex when Snf5 is deleted. In addition we have mapped the inter-subunit and intra-subunit interactions of the yeast SWI/SNF complex with lysine specific homo bi-functional crosslinkers and mass spectrometry. These data confirm the formation of a tri-subunit Snf5 sub-complex and show that this module uniquely interacts with the ATPase domain of the catalytic subunit of SWI/SNF (Snf2). These observations lead to a further investigation into the regulation of the remodeling activity of SWI/SNF by the Snf5 subunit. We have found that Snf5 is required for the ATPase domain to make stable interactions with nucleosomal DNA. And the loss of these interactions in turn also causes a reduction in the remodeling efficiency of the SWI/SNF complex. We have done additional mapping of the interactions of Snf5 as part of the SWI/SNF complex and find that the highly conserved region of yeast Snf5 corresponding to the human SNF5 protein associates with the surface of the nucleosome near the histone H2A-H2B dimer. We will discuss the relevance of these findings in highlighting how an aberrant form of SWI/SNF could be created by loss of Snf5 and provide an example of how it alters the normal function and structure of SWI/SNF. Citation Format: Blaine Bartholomew, Jim Persinger, Payel Sen, Mekonnen Dechassa Lemma, Jie Luo, Jeff Ranish. Changes in the architecture, interactions and chromatin remodeling of SWI/SNF due to loss of Snf5. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1972.