Project description:The E1A binding protein P300 (EP300, also known as p300, lysine acetyltransferase 3B or KAT3B) and its close paralogue CREB-binding protein (CREBBP, aka CBP or KAT3A) possess intrinsic histone acetyltransferase (HAT) activity that can act on both histone and non-histone proteins. P300 and CBP are composed of multiple conserved protein domains, many of which are in proximity to the HAT domain modulating its catalytic activity. Here we show that the TAZ2 domain regulates the intrinsic catalytic activity of p300 in vitro and histone acetylation and chromatin accessibility in cells. Our study extends the knowledge of p300 self-regulation and provides new therapeutic stratagies for human cancers with corresponding p300/CBP mutations.
Project description:The E1A binding protein P300 (EP300, also known as p300, lysine acetyltransferase 3B or KAT3B) and its close paralogue CREB-binding protein (CREBBP, aka CBP or KAT3A) possess intrinsic histone acetyltransferase (HAT) activity that can act on both histone and non-histone proteins. P300 and CBP are composed of multiple conserved protein domains, many of which are in proximity to the HAT domain modulating its catalytic activity. Here we show that the TAZ2 domain regulates the intrinsic catalytic activity of p300 in vitro and histone acetylation and chromatin accessibility in cells. Our study extends the knowledge of p300 self-regulation and provides new therapeutic stratagies for human cancers with corresponding p300/CBP mutations.
Project description:The E1A binding protein P300 (EP300, also known as p300, lysine acetyltransferase 3B or KAT3B) and its close paralogue CREB-binding protein (CREBBP, aka CBP or KAT3A) possess intrinsic histone acetyltransferase (HAT) activity that can act on both histone and non-histone proteins. P300 and CBP are composed of multiple conserved protein domains, many of which are in proximity to the HAT domain modulating its catalytic activity. Here we show that the TAZ2 domain regulates the intrinsic catalytic activity of p300 in vitro and histone acetylation and chromatin accessibility in cells. Our study extends the knowledge of p300 self-regulation and provides new therapeutic stratagies for human cancers with corresponding p300/CBP mutations.
Project description:p300 is a histone acetyltransferase that associates with crucial biological processes. p300 acetylates all four histones in the nucleosome, a basic unit of chromatin, and alters chromatin structure and dynamics. In this study, we performed structural and biochemical analysis to understand the nucleosome binding by p300. Crosslinking mass spectrometry suggests that the p300 catalytic core binds to nucleosomes in multiple binding forms to acetylate different histone tails.
Project description:The C-terminal activation domain (C-TAD) of the hypoxia-inducible transcription factors HIF-1? and HIF-2? binds the CH1 domains of the related transcriptional coactivators CREB-binding protein (CBP) and p300, an oxygen-regulated interaction thought to be highly essential for hypoxia-responsive transcription. The role of the CH1 domain in vivo is unknown, however. We created mutant mice bearing deletions in the CH1 domains (?CH1) of CBP and p300 that abrogate their interactions with the C-TAD, revealing that the CH1 domains of CBP and p300 are genetically non-redundant and indispensable for C-TAD transactivation function. Surprisingly, the CH1 domain was only required for an average of ~35-50% of global HIF-1?-responsive gene expression, whereas another HIF-transactivation mechanism that is sensitive to the histone deacetylase inhibitor trichostatin A (TSAS) accounts for ~70%. Both pathways are required for greater than 90% of the response for some target genes. Our findings suggest that a novel functional interaction between the protein acetylases CBP and p300, and deacetylases, is essential for nearly all HIF-responsive transcription. Experiment Overall Design: Three separate affymetrix experiments using mouse embryonic fibroblasts derived from embryos bearing the ?CH1 mutation in p300 and/or CBP and treated with hypoxia or combinations of dipyridyl (a hypoxia mimetic) and trichostatin A (a histone deacetylase inhibitor) are described (GSE3195, GSE3196 and GSE3296). Samples are not directly comparable between experiments because of differences in experiment design and Affymetrix chips used.
Project description:Human p300 is a transcriptional co-activator and a major acetyltransferase that acetylates histones and other proteins facilitating gene transcription. The activity of p300 relies on the fine-tuned interactome that involves a dozen p300 domains and hundreds of binding partners and links p300 to a wide range of vital signaling events. Here, we report on a novel function of the ZZ-type zinc finger (ZZ) of p300 as a reader of histone H3. We show that the ZZ domain and acetyllysine recognizing bromodomain (BD) of p300 play critical roles in modulating p300 enzymatic activity and its association with chromatin. Acetyllysine binding of BD is essential for acetylation of histones H3 and H4, whereas interaction of the ZZ domain with H3 promotes selective acetylation of histone H3K27 and H3K18.
Project description:Murine small intestinal organoids were cultured in the presence or absence of 3µM inhibitor I-CBP112 (PubChem CID 90488984), which targets E1A Binding Protein P300 (Ep300) and Creb-binding protein (Crebbp, Cbp). Organoids were grown in culture media containing EGF, Noggin and R-spondin (ENR), media was changed after 48h, and organoids were harvested after 96h.
Project description:Histone modifications, largely regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs) have been recognized as major regulatory mechanisms governing human diseases including cancer. Despite significant effort and recent advances, the mechanism by which the p300 transcriptional coactivator mediates tumorigenesis remains unclear. Here, we use a genetic and chemical approach to identify the Microphthalmia-associated transcription factor (MITF) as a critical downstream target of p300 driving human melanoma growth. We find that direct transcriptional control of MITF by p300-dependent histone acetylation within proximal gene regulatory regions is coupled to cellular proliferation, suggesting a significant growth regulatory axis. Further analysis revealed Forkhead Box M1 (FOXM1) as a key effector of the p300-MITF axis driving cell growth, which is selectively activated in human melanomas. Targeted chemical inhibition of p300 histone acetyltransferase activity using a potent and selective catalytic p300/CBP inhibitor confirmed the critical role of the p300-MITF-FOXM1 axis in melanoma and demonstrated significant growth inhibitory effects in melanoma cells expressing high levels of MITF. These data support p300 as a promising novel epigenetic therapeutic target in human melanoma.
Project description:The transcriptional co-activator and acetyltransferase p300 is required for fundamental cellular processes, including differentiation and growth. Here, we report that p300 forms phase separated condensates in the cell nucleus. The phase separation ability of p300 is regulated by autoacetylation and relies on its catalytic core components, including the HAT domain, the autoinhibition loop, and bromodomain. p300 condensates sequester chromatin components, such as histone H3 tail and DNA, and are amplified through binding of p300 to the nucleosome. The catalytic HAT activity of p300 is decreased due to occlusion of the active site in the phase separated droplets, a large portion of which co-localizes with chromatin regions enriched in H3K27me3. Our findings suggest a model in which p300 condensates can act as a storage pool of the protein with reduced HAT activity, allowing p300 to be compartmentalized and concentrated at poised or repressed chromatin regions.
Project description:Epigenetic events, including covalent post-translational modification of histones, have frequently been demonstrated to play critical roles in tumor development and progression. The transcriptional coactivator, p300/CBP, possesses both histone acetyltransferase (HAT) activity as well as scaffolding properties that directly influence transcriptional activation of targeted genes. We have used a recently reported small molecule inhibitor of p300 HAT activity, C646, to explore the specific contribution of p300/CBP HAT activity to tumor development and progression. We find that C646 inhibits the growth of lineage-specific tumor cell lines including human melanomas through direct transcriptional regulation of cell cycle regulatory proteins. Further evaluation of the p300 HAT transcriptome in human melanoma cells using comprehensive gene expression profiling reveals that p300 HAT activity globally promotes cell cycle progression, nucleosome assembly, and the DNA damage checkpoint through direct transcriptional regulatory mechanisms. Additionally, C646 promotes sensitivity to DNA damaging agents leading to enhanced apoptosis of melanoma cells following combination treatment with cisplatin. Together our data suggest that p300 HAT activity regulates critical growth regulatory pathways in tumors and may serve as a novel therapeutic target for melanoma and other malignancies by promoting cellular responses to DNA damaging agents. Keywords: p300, small molecule inhibitor, melanoma WM35 cells grown under normal culture conditions were treated for 6 and 24 hours with compound C646 to block p300 HAT activity. A vehicle control (DMSO) was included at each time point. RNA was extracted from all 4 samples using the Qiagen RNeasy kit. RNA quality check, labeling, hybridization, initial data processing and analysis was performed by the JHMI Microarray Core Facility. Affymetrix GeneChip Human Exon 1.0 ST Array was used for this study.