Broad Institute Screen for Small Molecule Inhibitors of ATP Dependent Chromatin Remodeling Inhibitor Probe Project
Identify small-molecule inhibitors of the BAF complex, which modulates chromatin structure in embryonic stem cells and is essential for the maintenance of self-renewal and pluripotency . The identified inhibitor will be a powerful research tool to understand the poorly defined mechanisms used by this complex to promote pluripotency and suppress tumors. ..more
Gerald Crabtree,Stanford University,firstname.lastname@example.org,(650) 723-3685
Emily Dykhuize,Stanford University,email@example.com,(650) 725-5820
Identify small-molecule inhibitors of the BAF complex, which modulates chromatin structure in embryonic stem cells and is essential for the maintenance of self-renewal and pluripotency . The identified inhibitor will be a powerful research tool to understand the poorly defined mechanisms used by this complex to promote pluripotency and suppress tumors.
Mouse embryonic stem cells, ATP-dependent chromatin-remodeling complex, esBAF, Bmi1, cell-based reporter assay, inhibitor screen
An essential component of the embryonic stem cell (ESC) core pluripotency transcriptional network is the SWI/SNF-like ATP-dependent chromatin-remodeling complex. Mammalian SWI/SNF complexes are composed of a central ATPase (BRG1 or BRM) and 10-12 subunits (referred to as BAFs for BRG1 or BRM-associated factors). Embryonic stem cells (ESCs) express a unique assembly of subunits, called esBAF, which cannot be functionally rescued by the expression of alternate, homologous subunits. The combination of BAF subunits is cell type specific, and subunit switching is an important determinant of differentiation.
In addition to the essential role of BAF in pluripotency and development, several BAF subunits have been confirmed as tumor suppressors in humans. Bi-allelic loss of the BAF47 (hSNF5, ini) gene has been found in nearly 100% of human malignant rhabdoid tumors, which are highly aggressive early childhood tumors found in the kidney, lung, soft-tissue or brain. The ATPase subunits, Brm and Brg also have tumor suppressor qualities. Brm loss has been correlated with human lung, prostate, and gastric cancer, while bi-allelic mutations in Brg have been reported in human prostate, lung, breast, and pancreatic cancer cell lines. Considering the evidence linking misregulation of the BAF complex to cancer initiation, progression, and therapeutic resistance, further understanding of the mechanism of the BAF complex is crucial for understanding the link between chromatin remodeling and tumor biology.
Although SWI/SNF complexes in Saccharomyces cerevisiae exclusively activate genes, microarray studies in mouse ESCs reveal a predominantly repressive role for esBAF (approximately 70% of direct esBAF regulated genes are repressed). To further complicate matters, esBAF predominantly represses targets at sites distal to the promoters; only 12% of esBAF binding occurs at promoters. It is unclear how the esBAF complex can be acting in such a manner, and previous mechanistic studies have only revealed small glimpses of the whole picture. To facilitate deciphering the elusive mechanism of the BAF complex, we plan to use small molecule inhibitors to identify and order the series of reactions catalyzed by the esBAF complex.