Project description:Somatic progenitors suppress differentiation to maintain tissue self-renewal. While epigenetic regulators of DNA and histone modifications can support such repression, a role for nuclear actin-like proteins is unclear. In epidermis, ACTL6a/BAF53A was found enriched in progenitors and down-regulated during differentiation. Conditional ACTL6a deletion abolished epidermal self-renewal and induced terminal differentiation, whereas ectopically expressed ACTL6a suppressed differentiation. Among known activators of epidermal differentiation, KLF4 was found to control 227 genes also regulated by ACTL6a. ACTL6a loss upregulated KLF4 and its target genes, effects that were blocked by KLF4 depletion. Among multiple ACTL6a-interacting epigenetic regulators, the SWI/SNF complex was required for KLF4 activation and differentiation. In progenitors, ACTL6a loss led to enhanced SWI/SNF binding to the promoters of KLF4 and other differentiation genes. ACTL6a thus maintains the undifferentiated progenitor state, in part by suppressing SWI/SNF complex-enabled induction of KLF4. Gene expression analysis: To identify the gene set controlled by ACTL6a in human keratinocyte. Total RNA was isolated in biologic duplicate from cells with ACTL6a loss as compared to controls, and hybridized to Affymetrix HG-U133 2.0 Plus arrays.
Project description:Somatic progenitors suppress differentiation to maintain tissue self-renewal. While epigenetic regulators of DNA and histone modifications can support such repression, a role for nuclear actin-like proteins is unclear. In epidermis, ACTL6a/BAF53A was found enriched in progenitors and down-regulated during differentiation. Conditional ACTL6a deletion abolished epidermal self-renewal and induced terminal differentiation, whereas ectopically expressed ACTL6a suppressed differentiation. Among known activators of epidermal differentiation, KLF4 was found to control 227 genes also regulated by ACTL6a. ACTL6a loss upregulated KLF4 and its target genes, effects that were blocked by KLF4 depletion. Among multiple ACTL6a-interacting epigenetic regulators, the SWI/SNF complex was required for KLF4 activation and differentiation. In progenitors, ACTL6a loss led to enhanced SWI/SNF binding to the promoters of KLF4 and other differentiation genes. ACTL6a thus maintains the undifferentiated progenitor state, in part by suppressing SWI/SNF complex-enabled induction of KLF4.
Project description:Loss-of-function mutations in SWI/SNF chromatin remodeling subunit genes are observed in many cancers, but an oncogenic role for SWI/SNF is not well established. Here we reveal that ACTL6A, encoding a SWI/SNF subunit linked to stem and progenitor cell function, is frequently co-amplified and highly expressed together with the p53 family member p63 in head and neck squamous cell carcinoma (HNSCC). ACTL6A and p63 physically interact and cooperatively control a transcriptional program that promotes proliferation and suppresses differentiation, in part through activation of the Hippo-YAP pathway via regulators including WWC1. Consequently, loss of ACTL6A or p63 in tumor cells induces YAP phosphorylation and inactivation, associated with growth arrest and terminal differentiation, all phenocopied by WWC1 overexpression. In vivo, ectopic ACTLC6A/p63 expression promotes tumorigenesis, while ACTL6A expression and YAP activation are highly correlated in primary HNSCC and predict poor patient survival. Thus, ACTL6A and p63 collaborate as oncogenic drivers in HNSCC.
Project description:Loss-of-function mutations in SWI/SNF chromatin remodeling subunit genes are observed in many cancers, but an oncogenic role for SWI/SNF is not well established. Here we reveal that ACTL6A, encoding a SWI/SNF subunit linked to stem and progenitor cell function, is frequently co-amplified and highly expressed together with the p53 family member p63 in head and neck squamous cell carcinoma (HNSCC). ACTL6A and p63 physically interact and cooperatively control a transcriptional program that promotes proliferation and suppresses differentiation, in part through activation of the Hippo-YAP pathway via regulators including WWC1. Consequently, loss of ACTL6A or p63 in tumor cells induces YAP phosphorylation and inactivation, associated with growth arrest and terminal differentiation, all phenocopied by WWC1 overexpression. In vivo, ectopic ACTLC6A/p63 expression promotes tumorigenesis, while ACTL6A expression and YAP activation are highly correlated in primary HNSCC and predict poor patient survival. Thus, ACTL6A and p63 collaborate as oncogenic drivers in HNSCC. Gene expression profiling of HNSCC cells with and without ablated endogenous ACTL6A via lentiviral shRNA.
Project description:Loss-of-function mutations in SWI/SNF chromatin remodeling subunit genes are observed in many cancers, but an oncogenic role for SWI/SNF is not well established. Here we reveal that ACTL6A, encoding a SWI/SNF subunit linked to stem and progenitor cell function, is frequently co-amplified and highly expressed together with the p53 family member p63 in head and neck squamous cell carcinoma (HNSCC). ACTL6A and p63 physically interact and cooperatively control a transcriptional program that promotes proliferation and suppresses differentiation, in part through activation of the Hippo-YAP pathway via regulators including WWC1. Consequently, loss of ACTL6A or p63 in tumor cells induces YAP phosphorylation and inactivation, associated with growth arrest and terminal differentiation, all phenocopied by WWC1 overexpression. In vivo, ectopic ACTLC6A/p63 expression promotes tumorigenesis, while ACTL6A expression and YAP activation are highly correlated in primary HNSCC and predict poor patient survival. Thus, ACTL6A and p63 collaborate as oncogenic drivers in HNSCC. Gene expression profiling of untransformed keratinocytes (HaCaT) with and without ablated endogenous p63 via lentiviral shRNA.
Project description:Loss-of-function mutations in SWI/SNF chromatin remodeling subunit genes are observed in many cancers, but an oncogenic role for SWI/SNF is not well established. Here we reveal that ACTL6A, encoding a SWI/SNF subunit linked to stem and progenitor cell function, is frequently co-amplified and highly expressed together with the p53 family member p63 in head and neck squamous cell carcinoma (HNSCC). ACTL6A and p63 physically interact and cooperatively control a transcriptional program that promotes proliferation and suppresses differentiation, in part through activation of the Hippo-YAP pathway via regulators including WWC1. Consequently, loss of ACTL6A or p63 in tumor cells induces YAP phosphorylation and inactivation, associated with growth arrest and terminal differentiation, all phenocopied by WWC1 overexpression. In vivo, ectopic ACTLC6A/p63 expression promotes tumorigenesis, while ACTL6A expression and YAP activation are highly correlated in primary HNSCC and predict poor patient survival. Thus, ACTL6A and p63 collaborate as oncogenic drivers in HNSCC. Gene expression profiling of HNSCC cells with and without ablated endogenous p63 via lentiviral shRNA
Project description:ACTL6A has been identified as a transcriptional regulator and driving pathways that are of specific benefit to the malignant elements within the tumor. Here, we aimed to find genes that are regulated by ACTL6A by CUT&Tag. BRG1 is the catalytic subunit of the SWI/SNF chromatin-remodeling complex. Nuclear factor (erythroid-derived 2)-like 2 (NFE2L2, NRF2) is a transcription factor that governs the antioxidant pathway. IgG was used as a control.
Project description:Cells need to integrate chemical and physical signals into transcriptional programs. In the peripheral nerves, axonal caliber selection by specialized Schwann cells, is critical for developmental myelination. However, only mechanisms through which Schwann cells sense chemical signals are well characterized. We identify ACtin-Like protein 6a (ACTL6a), a component of the SWI/SNF chromatin remodeling complex, as critical for axonal caliber recognition and developmental myelination. ACTL6a is expressed in the developing nerve and, when activated by contact with axons or nanofibers of specific caliber, it promotes the eviction of repressive histone marks thereby enhancing the transcriptional program of myelination. Mutant mice with Schwann cells lacking ACTL6a display aberrant recognition of axonal caliber, resulting in defective radial sorting and lower levels of transcripts regulating myelination of developing nerves. We suggest that developing peripheral nerves require an ACTL6a-dependent integration of physical and chemical signals in Schwann cells to release of repressive histone modifications and promote myelination.
Project description:While oncogenes can potentially be inhibited with small molecules, the loss of tumor suppressors is more common and is problematic because the tumor suppressor proteins are no longer present to be targeted. Notable examples include SMARCB1-mutant cancers, which are highly lethal malignancies driven by the inactivation of a subunit of SWI/SNF chromatin remodeling complexes. To generate mechanistic insight into the consequences of SMARCB1 mutation and to identify vulnerabilities, we contributed 14 SMARCB1-mutant cell lines to a near genome-wide CRISPR screen as part of the Cancer Dependency Map Project1-3. Here, we report that the little-studied gene DDB1-CUL4 Associated Factor 5 (DCAF5) is required for the survival of SMARCB1-mutant cancers. We show that DCAF5 serves a quality control function for SWI/SNF complexes and promotes degradation of incompletely assembled SWI/SNF complexes in the absence of SMARCB1. Upon depletion of DCAF5, SMARCB1-deficient SWI/SNF complexes re-accumulate, bind to target loci, and restore SWI/SNF-mediated gene expression to levels sufficient to reverse the cancer state, including in vivo. Consequently, cancer results not from the loss of SMARCB1 function per se but rather from DCAF5-mediated degradation of SWI/SNF complexes. These data indicate that therapeutic targeting of ubiquitin-mediated quality control factors may effectively reverse the malignant state of some cancers driven by disruption of tumor suppressor complexes.
Project description:While oncogenes can potentially be inhibited with small molecules, the loss of tumor suppressors is more common and is problematic because the tumor suppressor proteins are no longer present to be targeted. Notable examples include SMARCB1-mutant cancers, which are highly lethal malignancies driven by the inactivation of a subunit of SWI/SNF chromatin remodeling complexes. To generate mechanistic insight into the consequences of SMARCB1 mutation and to identify vulnerabilities, we contributed 14 SMARCB1-mutant cell lines to a near genome-wide CRISPR screen as part of the Cancer Dependency Map Project1-3. Here, we report that the little-studied gene DDB1-CUL4 Associated Factor 5 (DCAF5) is required for the survival of SMARCB1-mutant cancers. We show that DCAF5 serves a quality control function for SWI/SNF complexes and promotes degradation of incompletely assembled SWI/SNF complexes in the absence of SMARCB1. Upon depletion of DCAF5, SMARCB1-deficient SWI/SNF complexes re-accumulate, bind to target loci, and restore SWI/SNF-mediated gene expression to levels sufficient to reverse the cancer state, including in vivo. Consequently, cancer results not from the loss of SMARCB1 function per se but rather from DCAF5-mediated degradation of SWI/SNF complexes. These data indicate that therapeutic targeting of ubiquitin-mediated quality control factors may effectively reverse the malignant state of some cancers driven by disruption of tumor suppressor complexes.