Investigating post-translational control of SWI/SNF proteins

About This Grant

PROJECT SUMMARY Nearly 25% of cancers carry mutations in genes encoding components of SWI/SNF chromatin remodeling complexes, making SWI/SNF the most frequently mutated epigenetic regulator in cancer. SWI/SNF complexes facilitate lineage-specific gene expression by repositioning nucleosomes to enable transcription factor binding and by antagonizing the Polycomb repressive complexes (PRC2). Key to its function is heterogeneity of SWI/SNF complex composition, driven by unique subunits that define each of the three SWI/SNF sub-complex families and incorporation of mutually exclusive paralog proteins at several positions in the complex, which confers specificity of interaction with different transcription factors and histone modifications. Mutations that disrupt SWI/SNF function perturb complex integrity, disrupt PRC2 antagonism, and impair lineage- specific gene expression, which in susceptible progenitor cell contexts promotes oncogenic transformation. Despite key roles of SWI/SNF in controlling cell fate and frequent mutations of genes encoding SWI/SNF subunits in cancer, the mechanisms that control SWI/SNF function are poorly understood. The Roberts Lab recently published that the little-studied E3-ubiquitin ligase adaptor protein, DCAF5, is a specific dependency in Rhabdoid Tumors (RT) cells, which are driven by lack of SWI/SNF subunit SMARCB1. This work showed that DCAF5 promotes the highly proliferative, cancerous cell state by degrading residual SWI/SNF complexes, thereby preventing activation of lineage-specifying genes. This study established DCAF5 as a compelling therapeutic target and drug discovery efforts are now underway. Despite being ubiquitously expressed and evolutionarily conserved, the role of DCAF5 in regulating SWI/SNF function in normal cells is unknown. This proposal aims to define how DCAF5 controls SWI/SNF complex composition and function in non- malignant cells, using biochemical and computational approaches in cell models derived from a conditional Dcaf5 mouse model. This proposal directly supports the applicant’s training goals by providing training and mentorship to perform rigorous experiments to systematically dissect complex biological problems, acquire computational skills for integrative analyses of genomic data, and provides ample opportunities to enhance mentorship skills and build a strong scientific network. This applicant is supported by a world-class research institute with state- of-the-art resources, a collaborative laboratory, a dedicated sponsor with an impressive record of training early- career scientists, and collaborators with additional expertise required to achieve the applicant’s training goals. Together, this proposal supports the applicant’s long-term goal to learn to rigorously interrogate impactful scientific questions as an independent investigator and will reveal novel mechanisms that control SWI/SNF complex activity, which is critical for understanding both the mechanisms by which SWI/SNF dysregulation drives cancer and the consequences of therapeutic targeting of DCAF5.