Group 3 medulloblastoma transcriptional networks collapse under domain specific EP300/CBP inhibition.

Chemical discovery efforts commonly target individual protein domains. Many proteins, including the EP300/CBP histone acetyltransferases (HATs), contain several targetable domains. EP300/CBP are critical gene-regulatory targets in cancer, with existing high potency inhibitors of either the catalytic HAT domain or protein-binding bromodomain (BRD). A domain-specific inhibitory approach to multidomain-containing proteins may identify exceptional-responding tumor types, thereby expanding a therapeutic index. Here, we discover that targeting EP300/CBP using the domain-specific inhibitors, A485 (HAT) or CCS1477 (BRD) have different effects in select tumor types. Group 3 medulloblastoma (G3MB) cells are especially sensitive to BRD, compared with HAT inhibition. Structurally, these effects are mediated by the difluorophenyl group in the catalytic core of CCS1477. Mechanistically, bromodomain inhibition causes rapid disruption of genetic dependency networks that are required for G3MB growth. These studies provide a domain-specific structural foundation for drug discovery efforts targeting EP300/CBP and identify a selective role for the EP300/CBP bromodomain in maintaining genetic dependency networks in G3MB.

EP300/CREBBP acetyltransferase inhibition limits steroid receptor and FOXA1 signaling in prostate cancer cells.

The androgen receptor (AR) is a primary target for treating prostate cancer (PCa), forming the bedrock of its clinical management. Despite their efficacy, resistance often hampers AR-targeted therapies, necessitating new strategies against therapy-resistant PCa. These resistances involve various mechanisms, including AR splice variant overexpression and altered activities of transcription factors like the glucocorticoid receptor (GR) and FOXA1. These factors rely on common coregulators, such as EP300/CREBBP, suggesting a rationale for coregulator-targeted therapies. Our study explores EP300/CREBBP acetyltransferase inhibition's impact on steroid receptor and FOXA1 signaling in PCa cells using genome-wide techniques. Results reveal that EP300/CREBBP inhibition significantly disrupts the AR-regulated transcriptome and receptor chromatin binding by reducing the AR-gene expression. Similarly, GR's regulated transcriptome and receptor binding were hindered, not linked to reduced GR expression but to diminished FOXA1 chromatin binding, restricting GR signaling. Overall, our findings highlight how EP300/CREBBP inhibition distinctively curtails oncogenic transcription factors' signaling, suggesting the potential of coregulatory-targeted therapies in PCa.

EP300-ZNF384 transactivates IL3RA to promote the progression of B-cell acute lymphoblastic leukemia.

The EP300-ZNF384 fusion gene is an oncogenic driver in B-cell acute lymphoblastic leukemia (B-ALL). In the present study, we demonstrated that EP300-ZNF384 substantially induces the transcription of IL3RA and the expression of IL3Rα (CD123) on B-ALL cell membranes. Interleukin 3 (IL-3) supplementation promotes the proliferation of EP300-ZNF348-positive B-ALL cells by activating STAT5. Conditional knockdown of IL3RA in EP300-ZF384-positive cells inhibited the proliferation in vitro, and induced a significant increase in overall survival of mice, which is attributed to impaired propagation ability of leukemia cells. Mechanistically, the EP300-ZNF384 fusion protein transactivates the promoter activity of IL3RA by binding to an A-rich sequence localized at -222/-234 of IL3RA. Furthermore, forced EP300-ZNF384 expression induces the expression of IL3Rα on cell membranes and the secretion of IL-3 in CD19-positive B precursor cells derived from healthy individuals. Doxorubicin displayed a selective killing of EP300-ZNF384-positive B-ALL cells in vitro and in vivo. Collectively, we identify IL3RA as a direct downstream target of EP300-ZNF384, suggesting CD123 is a potent biomarker for EP300-ZNF384-driven B-ALL. Targeting CD123 may be a novel therapeutic approach to EP300-ZNF384-positive patients, alternative or, more likely, complementary to standard chemotherapy regimen in clinical setting.

EP300 improves endothelial injury and mitochondrial dysfunction in coronary artery disease by regulating histone acetylation of SOCS1 promoter via inhibiting JAK/STAT pathway.

Endothelial cell injury and mitochondrial dysfunction are crucial events during coronary artery disease (CAD). Suppressor of cytokine signaling-1 (SOCS1) is a negative mediator for inflammation, but there are few reports regarding histone acetylation of SOCS1 in CAD. The aim of the current study is to examine the impact of SOCS1 in CAD patients and human umbilical vein endothelial cells (HUVECs). We enrolled patients with CAD and healthy volunteers. HUVECs treated with ox-LDL were used as in vitro model. This study showed that SOCS1 expression was decreased in patients with CAD and ox-LDL-stimulated HUVECs. Overexpressing SOCS1 ameliorated endothelial cell injury and mitochondrial dysfunction induced by ox-LDL in vitro. Moreover, EP300 promoted SOCS1 transcription through increasing the acetylation of SOCS1 and recruiting H3K27ac to the SOCS1 gene promoter in HUVECs induced by ox-LDL. Additionally, SOCS1 repressed JAK/STAT cascade in ox-LDL-stimulated HUVECs. Silencing of EP300 reversed endothelial cell injury and mitochondrial dysfunction ameliorated by overexpression of SOCS1 in ox-LDL-induced HUVECs. In summary, SOCS1 alleviated endothelial injury and mitochondrial dysfunction via enhancing H3K27ac acetylation by recruiting EP300 to promoter region and inhibiting JAK/STAT pathway. These results contribute to discover underlying diagnostic biomarkers and therapeutic targets for CAD.

Acetyltransferase P300 Regulates Glucose Metabolic Reprogramming through Catalyzing Succinylation in Lung Cancer.

Aberrant protein post-translational modification is a hallmark of malignant tumors. Lysine succinylation (Ksucc) plays a vital role in cell energy metabolism in various cancers. However, whether succinylation can be catalyzed by acetyltransferase p300 remains unclear. In this study, we unveiled that p300 is a "writer" for succinylation, and p300-mediated Ksucc promotes cell glycometabolism in lung adenocarcinoma (LUAD). Specifically, our succinylome data revealed that EP300 deficiency leads to the systemic reduction of Ksucc, and 79.55% of the p300-succinylated proteins were found in the cytoplasm, which were primarily enriched in the carbohydrate metabolism process. Interestingly, deleting EP300 led to a notable decrease in Ksucc levels on several glycolytic enzymes, especially Phosphoglycerate Kinase 1 (PGK1). Mutation of the succinylated site of PGK1 notably hindered cell glycolysis and lactic acid excretion. Metabolomics in vivo indicated that p300-caused metabolic reprogramming was mainly attributed to the altered carbohydrate metabolism. In addition, 89.35% of LUAD patients exhibited cytoplasmic localization of p300, with higher levels in tumor tissues than adjacent normal tissues. High levels of p300 correlated with advanced tumor stages and poor prognosis of LUAD patients. Briefly, we disclose the activity of p300 to catalyze succinylation, which contributes to cell glucose metabolic reprogramming and malignant progression of lung cancer.

Global crotonylome identifies EP300-regulated ANXA2 crotonylation in cumulus cells as a regulator of oocyte maturation.

Lysine crotonylation (Kcr), a newly discovered post-translational modification, played a crucial role in physiology and disease progression. However, the roles of crotonylation in oocyte meiotic resumption remain elusive. As abnormal cumulus cell development will cause oocyte maturation arrest and female infertility, we report that cumulus cells surrounding human meiotic arrested oocytes showed significantly lower crotonylation, which was associated with decreased EP300 expression and blocked cumulus cell expansion. In cultured human cumulus cells, exogenous crotonylation or EP300 activator promoted cell proliferation and reduced cell apoptosis, whereas EP300 knockdown induced the opposite effect. Transcriptome profiling analysis in human cumulus cells indicated that functions of crotonylation were associated with activation of epidermal growth factor receptor (EGFR) pathway. Importantly, we characterized the Kcr proteomics landscape in cumulus cells by LC-MS/MS analysis, and identified that annexin A2 (ANXA2) was crotonylated in cumulus cells in an EP300-dependent manner. Crotonylation of ANXA2 enhanced the ANXA2-EGFR binding, and then activated the EGFR pathway to affect cumulus cell proliferation and apoptosis. Using mouse oocytes IVM model and EP300 knockout mice, we further confirmed that crotonylation alteration in cumulus cells affected the oocyte maturation. Together, our results indicated that EP300-mediated crotonylation is important for cumulus cells functions and oocyte maturation.

EP300 promotes lung cancer cell proliferation by regulating the oncogenic transcription of Hippo-YAP signaling pathway.

The transcriptional activation function of YAP in cancer development has been widely studied. However, the underlying regulatory mechanisms remain largely unknown. In this study, we found that EP300, one histone acetyltransferase, interacted with YAP and was recruited into the phase separated condensates of YAP. Transcriptomic analysis revealed substantial alterations in gene expression upon EP300 depletion, with downregulated genes associated with cancer progression and Hippo-YAP pathway. Notably, disruption of EP300 inhibited the transcriptional activation of YAP and reduced the binding of H3K27ac on YAP target oncogenes in Hippo pathway. Moreover, depletion of EP300 effectively inhibited YAP-driven tumor growth. Taken together, these results indicate that EP300 contributes to lung cancer progression by promoting the oncogenic transcription of YAP through H3K27ac, which suggests that YAP-EP300 axis may be potential therapeutic targets for lung cancer treatment.

Ox-LDL promotes M1-like polarization of macrophages through the miR-21-5p/SKP2/EP300 pathway.

Oxidized low-density lipoprotein (ox-LDL) mediated inflammatory damage, which possibly induces atherosclerosis (AS); however, the role of miRNA in this process has rarely been reported. In this paper, we study the ox-LDL-related endothelial cell damage and changes of macrophages. The bioinformatics method was used to analyze the expression changes of miRNA in AS patients, luciferase assay was used to study the interaction of protein and miRNA, and co-IP and ubiquitination experiments were used to analyze protein interaction. Flow cytometry was used to detect the polarization of macrophages. Database analysis showed that the expression of miR-21-5p was upregulated in AS patients. Luciferase assay showed that miR-21-5p can bind to SKP2 and subsequently influence ubiquitination of EP300. Overexpression of EP300 strengthens the HMGB1-induced acetylation and subsequently mediates the dissociation of HMGB1 from SIRT1, and thus HMGB1 could be secreted outside the cell. The HMGB1 released from endothelial cells can promote macrophage M1 polarization. This study shows that ox-LDL activates the SKP2/EP300 pathway through promoting upregulation of miR-21-5p, thereby acetylating and secreting HMGB1 outside the endothelium, subsequently enhancing macrophage polarization to further stabilize the inflammation situation.

NDUFA8 is transcriptionally regulated by EP300/H3K27ac and promotes mitochondrial respiration to support proliferation and inhibit apoptosis in cervical cancer.

Cervical cancer, a common malignancy in women, poses a significant health burden worldwide. In this study, we aimed to investigate the expression, function, and potential mechanisms of NADH: ubiquinone oxidoreductase subunit A8 (NDUFA8) in cervical cancer. The Gene Expression Profiling Interactive Analysis (GEPIA) database and immunohistochemical scoring were used to analyze NDUFA8 expression in cervical cancer tissues and normal tissues. Quantitative real-time PCR and Western blot analyses were performed to assess the expression level of NDUFA8 in cervical cancer cell lines. NDUFA8 knockdown or overexpression experiments were conducted to evaluate its impact on cell proliferation and apoptosis. The mitochondrial respiratory status was analyzed by measuring cellular oxygen consumption, adenosine triphosphate (ATP) levels, and the expression levels of Mitochondrial Complex I activity, and Mitochondrial Complex IV-associated proteins Cytochrome C Oxidase Subunit 5B (COX5B) and COX6C. NDUFA8 exhibited high expression levels in cervical cancer tissues, and these levels were correlated with reduced survival rates. A significant upregulation of NDUFA8 expression was observed in cervical cancer cell lines compared to normal cells. Silencing NDUFA8 hindered cell proliferation, promoted apoptosis, and concurrently suppressed cellular mitochondrial respiration, resulting in decreased levels of available ATP. Conversely, NDUFA8 overexpression induced the opposite effects. Herein, we also found that E1A Binding Protein P300 (EP300) overexpression facilitated Histone H3 Lysine 27 (H3K27) acetylation enrichment, enhancing the activity of the NDUFA8 promoter region. NDUFA8, which is highly expressed in cervical cancer, is regulated by transcriptional control via EP300/H3K27 acetylation. By promoting mitochondrial respiration, NDUFA8 contributes to cervical cancer cell proliferation and apoptosis. These findings provide novel insights into NDUFA8 as a therapeutic target in cervical cancer.

MiR-26a-5p exerts its influence by targeting EP300, a molecule known for its role in activating the PI3K/AKT/mTOR signaling pathway in CD8+tumor-infiltrating lymphocytes of colorectal cancer.

Surgical resection remains the primary approach for treating colorectal cancer, which is among the prevalent types of cancers affecting the digestive system. Tumor-infiltrating lymphocyte (TIL) therapy has emerged as a prominent area of study in the field of tumor immunotherapy in recent times, with the potential to serve as a supplementary treatment for colorectal cancer. For this investigation, we employed single-cell sequencing data to assess the manifestation extent of miR-26a-5p exists in healthy colon tissue, tissue affected by colorectal cancer, and tissue adjacent to the tumor. According to our findings, tumor-infiltrating T lymphocytes express comparatively less miR-26a-5p in comparison to normal T lymphocytes, the role of it in modulating the function of tumor-infiltrating T lymphocytes is suggested. Studies on miR-26a-5p's involvement in tumor-infiltrating T lymphocytes is limited, despite previous evidence indicating its ability to facilitate the development and advancement of cancerous cells. As a result of our experiments, we concluded that miR-26a-5p hindered the PI3K/AKT/mTOR(PAM) signaling pathway, reducing the ability of CD8+ tumor-infiltrating cells eradicate tumors. Using bioinformatics tools, we utilized prediction methods to identify EP300 as the specific gene targeted by miR-26a-5p. Subsequent research understood that downregulation of EP300 counteracted the suppressive impact exerted by miR-26a-5p on the stimulation of PAM signaling pathway, while it also diminishes the viability and cytotoxicity of CD8+ tumor-infiltrating lymphocytes. Therefore, miR-26a-5p emerges as a compelling option for the effective control of TIL therapy.

PPARα Senses Bisphenol S to Trigger EP300-Mediated Autophagy Blockage and Hepatic Steatosis.

The internal exposure dose of bisphenol S (BPS) is increasing since its use as a substitute for BPA. The relationship between BPS and nonalcoholic liver disease (NAFLD) and the underlying mechanism remain unclarified. In this study, we evaluated the correlation of BPS with NAFLD in populations from the Jiangsu Survey and the 2013-2016 National Health Nutrition Examination Survey and unraveled the molecular pathway by which BPS blocked hepatic autophagy, contributing to lipid accumulation. The study found that serum and urine BPS were associated with NAFLD risks in both the Chinese and US populations. For each additional unit of the BPS level, the NAFLD risk increased by 3.163-fold (serum) and 3.979-fold (urine) in the Chinese population. In addition, after BPS exposure at a dose equivalent to human exposure for 20 weeks, mice developed liver lipid accumulation. BPS could trigger PPARα-mediated transcriptional activation of EP300 expression. BPS promoted the translocation of EP300 from the nucleus to the cytoplasm to regulate the acetylation of Raptor and the activation of mTORC1, which in turn induced autophagy blockage and interfered with lipid degradation in hepatocytes. Conversely, knockdown of EP300 reduced Raptor acetylation and ameliorated autophagy blockage. This study demonstrated that EP300 was a key enzyme for the development of BPS-related NAFLD and provided novel evidence that BPS causes NAFLD.

Therapeutic targeting of EP300/CBP by bromodomain inhibition in hematologic malignancies.

CCS1477 (inobrodib) is a potent, selective EP300/CBP bromodomain inhibitor which induces cell-cycle arrest and differentiation in hematologic malignancy model systems. In myeloid leukemia cells, it promotes rapid eviction of EP300/CBP from an enhancer subset marked by strong MYB occupancy and high H3K27 acetylation, with downregulation of the subordinate oncogenic network and redistribution to sites close to differentiation genes. In myeloma cells, CCS1477 induces eviction of EP300/CBP from FGFR3, the target of the common (4; 14) translocation, with redistribution away from IRF4-occupied sites to TCF3/E2A-occupied sites. In a subset of patients with relapsed or refractory disease, CCS1477 monotherapy induces differentiation responses in AML and objective responses in heavily pre-treated multiple myeloma. In vivo preclinical combination studies reveal synergistic responses to treatment with standard-of-care agents. Thus, CCS1477 exhibits encouraging preclinical and early-phase clinical activity by disrupting recruitment of EP300/CBP to enhancer networks occupied by critical transcription factors.

HDAC8-mediated inhibition of EP300 drives a transcriptional state that increases melanoma brain metastasis.

Melanomas can adopt multiple transcriptional states. Little is known about the epigenetic drivers of these cell states, limiting our ability to regulate melanoma heterogeneity. Here, we identify stress-induced HDAC8 activity as driving melanoma brain metastasis development. Exposure of melanocytes and melanoma cells to multiple stresses increases HDAC8 activation leading to a neural crest-stem cell transcriptional state and an amoeboid, invasive phenotype that increases seeding to the brain. Using ATAC-Seq and ChIP-Seq we show that increased HDAC8 activity alters chromatin structure by increasing H3K27ac and enhancing accessibility at c-Jun binding sites. Functionally, HDAC8 deacetylates the histone acetyltransferase EP300, causing its enzymatic inactivation. This, in turn, increases binding of EP300 to Jun-transcriptional sites and decreases binding to MITF-transcriptional sites. Inhibition of EP300 increases melanoma cell invasion, resistance to stress and increases melanoma brain metastasis development. HDAC8 is identified as a mediator of transcriptional co-factor inactivation and chromatin accessibility that drives brain metastasis.

The D129L protein of African swine fever virus interferes with the binding of transcriptional coactivator p300 and IRF3 to prevent beta interferon induction.

IMPORTANCE: African swine fever (ASF) is an acute, hemorrhagic, and severe porcine infectious disease caused by African swine fever virus (ASFV). ASF outbreaks severely threaten the global pig industries and result in serious economic losses. No safe and efficacious commercial vaccine is currently available except in Vietnam. To date, large gaps in the knowledge concerning viral biological characteristics and immunoevasion strategies have hindered the ASF vaccine design. In this study, we demonstrate that pD129L negatively regulates the type I interferon (IFN) signaling pathway by interfering with the interaction of the transcriptional coactivator p300 and IRF3, thereby inhibiting the induction of type I IFNs. This study reveals a novel immunoevasion strategy employed by ASFV, shedding new light on the intricate mechanisms for ASFV to evade the host immune responses.

Comparative Analysis of Drug-like EP300/CREBBP Acetyltransferase Inhibitors.

The human acetyltransferase paralogues EP300 and CREBBP are master regulators of lysine acetylation whose activity has been implicated in various cancers. In the half-decade since the first drug-like inhibitors of these proteins were reported, three unique molecular scaffolds have taken precedent: an indane spiro-oxazolidinedione (A-485), a spiro-hydantoin (iP300w), and an aminopyridine (CPI-1612). Despite increasing use of these molecules to study lysine acetylation, the dearth of data regarding their relative biochemical and biological potencies makes their application as chemical probes a challenge. To address this gap, here we present a comparative study of drug-like EP300/CREBBP acetyltransferase inhibitors. First, we determine the biochemical and biological potencies of A-485, iP300w, and CPI-1612, highlighting the increased potencies of the latter two compounds at physiological acetyl-CoA concentrations. Cellular evaluation shows that inhibition of histone acetylation and cell growth closely aligns with the biochemical potencies of these molecules, consistent with an on-target mechanism. Finally, we demonstrate the utility of comparative pharmacology by using it to investigate the hypothesis that increased CoA synthesis caused by knockout of PANK4 can competitively antagonize the binding of EP300/CREBBP inhibitors and demonstrate proof-of-concept photorelease of a potent inhibitor molecule. Overall, our study demonstrates how knowledge of the relative inhibitor potency can guide the study of EP300/CREBBP-dependent mechanisms and suggests new approaches to target delivery, thus broadening the therapeutic window of these preclinical epigenetic drug candidates.

EP300 promotes ferroptosis via HSPA5 acetylation in pancreatic cancer.

Ferroptosis is a form of regulated cell death characterized by oxidative injury-induced lipid peroxidation. However, the detailed protein post-translational modification regulatory mechanism of ferroptosis remains largely unknown. Here, we report that E1A binding protein P300 (EP300) acetyltransferase promotes ferroptosis in human pancreatic ductal adenocarcinoma (PDAC) cells via the acetylation of heat shock protein family A (Hsp70) member 5 (HSPA5), also known as GRP78 or BIP) on the site of K353. Acetylated HSPA5 loses its ability to inhibit lipid peroxidation and subsequent ferroptotic cell death. Genetic or pharmacological inhibition of EP300-mediated HSPA5 acetylation on K353 increases PDAC cell resistance to ferroptosis. Moreover, histone deacetylase 6 (HDAC6) limits HSPA5 acetylation and subsequent ferroptosis. Collectively, these findings not only identify regulatory pathways for HSPA5 acetylation during ferroptosis, but also highlight promising strategies to increase ferroptosis sensitivity in PDAC cells.

SETD1A-mediated H3K4me3 methylation upregulates lncRNA HOXC-AS3 and the binding of HOXC-AS3 to EP300 and increases EP300 stability to suppress the ferroptosis of NSCLC cells.

BACKGROUND: Histone methyltransferases are crucial regulators in non-small cell lung cancer (NSCLC) development. This study explored the mechanism of histone methyltransferase SET domain containing 1A (SETD1A)-mediated H3K4me2 methylation in NSCLC cell ferroptosis and provides novel targets for NSCLC treatment. METHODS: Upon downregulation of SETD1A in NSCLC cell lines, cell proliferation potential, malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione (GSH) activities, iron content, and SETD1A, long noncoding RNA HOXC cluster antisense RNA 3 (lncRNA HOXC-AS3), E1A binding protein p300 (EP300), glutathione peroxidase 4 (GPX4) expressions were determined via cell counting kit-8, ELISA, iron assay kits, RT-qPCR, and western blot. Enrichment levels of SETD1A and H3K4me3 in the HOXC-AS3 promotor were measured via chromatin immunoprecipitation, and the binding of HOXC-AS3 and EP300 was analyzed via RNA immunoprecipitation. Rescue experiments were performed to confirm their roles in NSCLC cell ferroptosis. Xenograft tumor models were established to validate the role of SETD1A in vivo. RESULTS: SETD1A, H3K4me3, HOXC-AS3, and EP300 were highly-expressed in NSCLC cells. Silencing SETD1A inhibited NSCLC cell proliferation, increased MDA and iron levels, and decreased SOD, GSH, and GPX4 levels. SETD1A downregulation reduced H3K4me3 level, HOXC-AS3 expression, the binding of HOXC-AS3 to EP300, and EP300 stability. Overexpression of HOXC-AS3 or EP300 reversed the promotion of silencing SETD1A on NSCLC cell ferroptosis. Silencing SETD1A reduced tumor volume and weight and positive rate of ki67 and increased ferroptosis through the HOXC-AS3/EP300 axis. CONCLUSION: SETD1A-mediated H3K4me2 methylation promoted HOXC-AS3 expression, binding of HOXC-AS3 to EP300, and EP300 stability, thereby suppressing NSCLC cell ferroptosis.

EP300 as a Molecular Integrator of Fibrotic Transcriptional Programs.

Fibrosis is a condition characterized by the excessive accumulation of extracellular matrix proteins in tissues, leading to organ dysfunction and failure. Recent studies have identified EP300, a histone acetyltransferase, as a crucial regulator of the epigenetic changes that contribute to fibrosis. In fact, EP300-mediated acetylation of histones alters global chromatin structure and gene expression, promoting the development and progression of fibrosis. Here, we review the role of EP300-mediated epigenetic regulation in multi-organ fibrosis and its potential as a therapeutic target. We discuss the preclinical evidence that suggests that EP300 inhibition can attenuate fibrosis-related molecular processes, including extracellular matrix deposition, inflammation, and epithelial-to-mesenchymal transition. We also highlight the contributions of small molecule inhibitors and gene therapy approaches targeting EP300 as novel therapies against fibrosis.

The deubiquitinase UCHL3 mediates p300-dependent chemokine signaling in alveolar type II cells to promote pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic, fatal, fibrotic, interstitial lung disease of unknown cause. Despite extensive studies, the underlying mechanisms of IPF development remain unknown. Here, we found that p300 was upregulated in multiple epithelial cells in lung samples from patients with IPF and mouse models of lung fibrosis. Lung fibrosis was significantly diminished by the alveolar type II (ATII) cell-specific deletion of the p300 gene. Moreover, we found that ubiquitin C-terminal hydrolase L3 (UCHL3)-mediated deubiquitination of p300 led to the transcriptional activation of the chemokines Ccl2, Ccl7, and Ccl12 through the cooperative action of p300 and C/EBPß, which consequently promoted M2 macrophage polarization. Selective blockade of p300 activity in ATII cells resulted in the reprogramming of M2 macrophages into antifibrotic macrophages. These findings demonstrate a pivotal role for p300 in the development of lung fibrosis and suggest that p300 could serve as a promising target for IPF treatment.