Project description:KAT2A is a histone acetyl-transferase involved in stabilization of transcriptional activity through acetylation of lysine residue 9 of Histone 3. Mouse knockout models suggest that Kat2a is dispensable for haematopoietic stem and progenitor cell activity, despite a central role in survival and maintenance of Acute Myekoid Leukaemia cells through block of differentiation. Herein, we investigate KAT2A activity in human cord blood haematopoiesis and identify a specific requirement in the establishment of the erythroid lineage. KAT2A is required for specification and survival of Erythroid-Megakaryocytic progenitors, with regulation of expression of the erythropoietin receptor (EPOR) gene, which participates in lineage commitment, as well as of later effector genes in the platelet and erythroid lineages. Early and late lineage roles can be distinctly attributed to the ATAC and SAGA complexes in which context KAT2A exerts its activity. ATAC is active earlier in erythroid lineage development and mediates MEP specification from HSC, whilst SAGA activity is required post-commitment, including in expression of haemoglobin genes. We thus position KAT2A as a novel regulator of human erythropoiesis and separate early and later effects in lineage development with complex specificity. This has implications for putative therapeutic targeting of KAT2A complexes in leukaemia.
Project description:KAT2A is a histone acetyl-transferase involved in stabilization of transcriptional activity through acetylation of lysine residue 9 of Histone 3. Mouse knockout models suggest that Kat2a is dispensable for haematopoietic stem and progenitor cell activity, despite a central role in survival and maintenance of Acute Myekoid Leukaemia cells through block of differentiation. Herein, we investigate KAT2A activity in human cord blood haematopoiesis and identify a specific requirement in the establishment of the erythroid lineage. KAT2A is required for specification and survival of Erythroid-Megakaryocytic progenitors, with regulation of expression of the erythropoietin receptor (EPOR) gene, which participates in lineage commitment, as well as of later effector genes in the platelet and erythroid lineages. Early and late lineage roles can be distinctly attributed to the ATAC and SAGA complexes in which context KAT2A exerts its activity. ATAC is active earlier in erythroid lineage development and mediates MEP specification from HSC, whilst SAGA activity is required post-commitment, including in expression of haemoglobin genes. We thus position KAT2A as a novel regulator of human erythropoiesis and separate early and later effects in lineage development with complex specificity. This has implications for putative therapeutic targeting of KAT2A complexes in leukaemia.
Project description:The SAGA transcriptional co-activator complex regulates gene expression through histone acetylation at promoters, mediated by its histone acetyl transferase, KAT2A. While its structure and function have been extensively investigated, how the stability of individual subunits of SAGA, including KAT2A, is regulated, remains unclear. Here, using a fluorescence-based KAT2A stability reporter, we systematically dissect the molecular dependencies controlling KAT2A protein abundance. We identify the non-enzymatic SAGA CORE module subunits—TADA1, TAF5L, and TAF6L— as necessary for KAT2A stability, with loss of these subunits disrupting the integrity of SAGA, leading to non-chromatin-bound KAT2A that is degraded by the proteasome, consequently leading to reduced H3K9 acetylation. Proteomic profiling reveals progressive loss of CORE and HAT components upon acute disruption of the SAGA CORE, indicating that an intact CORE is required for the stability of numerous components of SAGA. Finally, a focused CRISPR screen of ubiquitin-proteasome system genes identifies the E3 ligase UBR5, a known regulator of orphan protein degradation, and the deubiquitinase OTUD5, as regulators of KAT2A degradation when the SAGA CORE is perturbed. Together, these findings reveal a dependency of KAT2A protein stability on SAGA CORE integrity and define an orphan quality control mechanism targeting unassembled KAT2A, revealing a potential vulnerability in SAGA-driven malignancies.
Project description:Alterations in chromatin accessibility independent of DNA methylation can affect cancer-related gene expression, but are often overlooked in conventional epigenomic profiling approaches. In this study, we describe a cost-effective and computationally simple assay called AcceSssIble to simultaneously interrogate DNA methylation and chromatin accessibility alterations in primary human clear cell renal cell carcinomas (ccRCC). Our study revealed significant perturbations to the ccRCC epigenome, and identified gene expression changes that were specifically attributed to the chromatin accessibility status whether or not DNA methylation was involved. Compared to commonly mutated genes in ccRCC, such as the von Hippel-Lindau (VHL) tumor suppressor, the genes identified by AcceSssIble comprised distinct pathways and more frequently underwent epigenetic changes, suggesting that genetic and epigenetic alterations could be independent events in ccRCC. Specifically, we found unique DNA methylation-independent promoter accessibility alterations in pathways mimicking VHL deficiency. Overall, this study provides a novel approach for identifying new epigenetic-based therapeutic targets, previously undetectable by DNA methylation studies alone, that may complement current genetic-based treatment strategies. Examination of 3 different histone modifications in 2 patient tumor and adjacent normal samples.
Project description:The SAGA transcriptional co-activator complex regulates gene expression through histone acetylation at promoters, mediated by its histone acetyl transferase, KAT2A. While its structure and function have been extensively investigated, how the stability of individual subunits of SAGA, including KAT2A, is regulated, remains unclear. Here, using a fluorescence-based KAT2A stability reporter, we systematically dissect the molecular dependencies controlling KAT2A protein abundance. We identify the non-enzymatic SAGA CORE module subunits—TADA1, TAF5L, and TAF6L— as necessary for KAT2A stability, with loss of these subunits disrupting the integrity of SAGA, leading to non-chromatin-bound KAT2A that is degraded by the proteasome, consequently leading to reduced H3K9 acetylation. Proteomic profiling reveals progressive loss of CORE and HAT components upon acute disruption of the SAGA CORE, indicating that an intact CORE is required for the stability of numerous components of SAGA. Finally, a focused CRISPR screen of ubiquitin-proteasome system genes identifies the E3 ligase UBR5, a known regulator of orphan protein degradation, and the deubiquitinase OTUD5, as regulators of KAT2A degradation when the SAGA CORE is perturbed. Together, these findings reveal a dependency of KAT2A protein stability on SAGA CORE integrity and define an orphan quality control mechanism targeting unassembled KAT2A, revealing a potential vulnerability in SAGA-driven malignancies.
Project description:Single-cell RNA sequencing analysis of RUNX1-RUNX1T1(9a) transformed c-kit positive cells with (Kat2a WT) and without Kat2a (Kat2a NULL). Lineage negative bone marrow cells were collected from Kat2a fl/fl Mx1-Cre-/- and Kat2a fl/fl Mx1-Cre +/- animals after pIpC treatment and transduced with RUNX1-RUNX1T1(9a) expressing retrovirus (reported by GFP expression). Cells were injected into irradiated C57BL6 mice and GFP positive c-Kit positive bone marrow cells collected 2 and 4 months after transplantation. Cells were processed for single-cell RNA sequencing library preparation (10X chromium single cell) and next gene sequencing following 10X genomics v2 protocol.
Project description:The mammalian epidermis undergoes constant renewal replenished by a pool of stem cells and terminal differentiation of their progeny. This is accompanied by changes in gene expression and morphology orchestrated, in part, by epigenetic modifiers. Here, we defined the role of histone acetyltransferase KAT2A in epidermal homeostasis and provided a comparative analysis that revealed key functional divergence with its paralogue, KAT2B. In contrast to KAT2B's reported function in epidermal differentiation, KAT2A supports the undifferentiated state in keratinocytes. RNA-seq analysis of KAT2A- and KAT2B- depleted keratinocytes revealed dysregulated epidermal differentiation. Depletion of KAT2A led to premature expression of epidermal differentiation genes in the absence of inductive signals, whilst loss of KAT2B delayed differentiation. KAT2A acetyltransferase activity was indispensable in regulating epidermal differentiation gene expression. The metazoan-specific N-terminus of KAT2A was also required to support its function in keratinocytes. We further showed that the interplay between KAT2A- and KAT2B- mediated regulation was important for normal cutaneous wound healing in vivo. Overall, these findings reveal a distinct mechanism in which keratinocytes utilize a pair of highly homologous histone acetyltransferases to support divergent functions in self-renewal and differentiation processes.
Project description:The PDGF and mTOR pathways are clinically relevant therapeutic targets in clear cell renal cell carcinoma (ccRCC), but the molecular mechanisms that lead to their activation has remained poorly understood. By chromatin and transcriptomic profiling and functional analysis we have identified Kruppel like factor 6 (KLF6), a transcription factor of the zinc-finger family, as a critical regulator of the PDGF-mTOR axis in ccRCC. KLF6 expression is supported by one of the strongest super enhancers in ccRCC cells. Inhibition of KLF6 in several ccRCC cell lines impaired cell proliferation in vitro and in vivo and reduced metastatic lung colonization. KLF6 depletion led to downregulation of lipid homeostasis pathways downstream of SREBF1 and SREBF2, suggesting a role for KLF6 as a regulator of mTOR. We find that KLF6 modulates mTORC1 activity in ccRCC via transcriptionally regulating the expression of PDGFB, an activator of the PIK3-AKT-mTOR signalling pathway. Targeting PDGFB in ccRCC inhibited mTORC1, and supplementing KLF6-depleted cells with recombinant PDGFB rescued mTORC1 activity. Our data suggest that a robust super enhancer that integrates signals from multiple pathways, including the ccRCC-initiating VHL-HIF2A pathway, supports an autocrine PDGFB-dependent signalling loop that promotes mTOR activity in ccRCC. These results suggest the possibility that combining low dose PDGFR and mTOR inhibition could be a viable therapeutic strategy for ccRCC.