61 research outputs found

    Dynamics of BAF- Polycomb Complex Opposition on Heterochromatin in Normal and Oncogenic States

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    The opposition between polycomb repressive complexes (PRC) and BAF (mSWI/SNF) complexes plays critical roles in development and disease. Mutations in the genes encoding BAF subunits contribute to over 20% of human malignancy, yet the underlying mechanisms remain unclear owing largely to a lack of assays to assess BAF function in vivo. To address this, we have developed a widely applicable recruitment assay system and find that BAF opposes PRC by rapid, ATP-dependent eviction, leading to the formation of accessible chromatin. Reversing this process results in reassembly of facultative heterochromatin. Surprisingly, BAF-mediated PRC eviction occurs in the absence of PolII occupancy, transcription, and replication. Further, we find that tumor suppressor and oncogenic BAF complex mutations result in differential effects on PRC eviction. These studies define a mechanistic sequence underlying the resolution and formation of facultative heterochromatin and demonstrate that BAF opposes polycomb complexes on a minute-by-minute basis to provide epigenetic plasticity

    A disordered region controls cBAF activity via condensation and partner recruitment

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    Intrinsically disordered regions (IDRs) represent a large percentage of overall nuclear protein content. The prevailing dogma is that IDRs engage in non-specific interactions because they are poorly constrained by evolutionary selection. Here, we demonstrate that condensate formation and heterotypic interactions are distinct and separable features of an IDR within the ARID1A/B subunits of the mSWI/SNF chromatin remodeler, cBAF, and establish distinct sequence grammars underlying each contribution. Condensation is driven by uniformly distributed tyrosine residues, and partner interactions are mediated by non-random blocks rich in alanine, glycine, and glutamine residues. These features concentrate a specific cBAF protein-protein interaction network and are essential for chromatin localization and activity. Importantly, human disease-associated perturbations in ARID1B IDR sequence grammars disrupt cBAF function in cells. Together, these data identify IDR contributions to chromatin remodeling and explain how phase separation provides a mechanism through which both genomic localization and functional partner recruitment are achieved

    A functional mammalian display screen identifies rare antibodies that stimulate NK cell-mediated cytotoxicity.

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    Therapies that boost the antitumor immune response have shown a great deal of success. Although most of these therapies have focused on enhancing T cell functions, there is a growing interest in developing therapies that can target other immune cell subsets. Like T cells, natural killer (NK) cells are cytotoxic effector cells that play a key role in the antitumor response. To advance the development of NK-based therapies, we developed a functional screen to rapidly identify antibodies that can activate NK cells. We displayed antibodies on a mammalian target cell line and probed their ability to stimulate NK cell-mediated cytotoxicity. From this screen, we identified five antibodies that bound with high affinity to NK cells and stimulated NK cell-mediated cytotoxicity and interferon-γ (IFN-γ) secretion. We demonstrate that these antibodies can be further developed into bispecific antibodies to redirect NK cell-mediated cytotoxicity toward CD20+ B cell lymphoma cells and HER2+ breast cancer cells. While antibodies to two of the receptors, CD16 and NCR1, have previously been targeted as bispecific antibodies to redirect NK cell-mediated cytotoxicity, we demonstrate that bispecific antibodies targeting NCR3 can also potently activate NK cells. These results show that this screen can be used to directly identify antibodies that can enhance antitumor immune responses
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