Recruitment Of Histone Acetyltransferases Research Articles

Small molecules that targeting p53 Y220C protein: mechanisms, structures, and clinical advances in anti-tumor therapy.

The p53 protein is regarded as the "Guardian of the Genome," but its mutation is tumor progression and present in more than half of malignant tumors. The pro-metastatic property of mutant p53 makes a strong argument for targeting mutant p53 with new therapeutic strategies. However, mutant p53 was considered as a challenging target for drug discovery due to the lack of small molecular binding pockets. Among them, mutant p53 Y220C creates a narrow crevice since the side chains dynamics on protein surface, which is suitable for designing small molecules to occupy the cavity and recovery the tumor suppressing function. Here, we describe the mechanism of p53 related signal pathway and how p53 Y220C regulate the tumorigenesis. We review the two types of p53 Y220C modulators including restoring the conformation of mutant p53 Y220C protein to wild-type p53 protein and recruiting histone acetyltransferase p300/CBP to acetylate p53 Y220C thus enables p53 Y220C dependent upregulation of apoptotic genes and downregulation of DNA damage response pathways. We also report clinical advances and challenges of these molecules in p53 Y220C medicated tumor therapy.

Increased COX6A2 promotes pancreatic β-cell apoptosis and is suppressed in diabetic GK rats after Roux-en-Y gastric bypass.

Roux-en-Y gastric bypass (RYGB) has been shown to inhibit β-cell apoptosis, but the underlying mechanisms are not yet fully understood. Cytochrome c oxidase subunit 6A2 (COX6A2) is expressed in β-cells. Here, we sought to investigate the role of COX6A2 in β-cell apoptosis, especially following RYGB. We found that RYGB significantly reduced β-cell apoptosis, accompanied by decreased COX6A2 expression in islets from diabetic Goto-Kakizaki (GK) rats. It is noteworthy that overexpression of COX6A2 promoted β-cell apoptosis, whereas COX6A2 deficiency suppressed it, suggesting the pro-apoptotic role of COX6A2 in β-cells. Mechanistically, increased COX6A2 interacted with and upregulated the expression of cyclophilin D (CypD), facilitating the release of cytochrome c from mitochondria to the cytoplasm, thereby promoting β-cell apoptosis. Furthermore, high-glucose-activated ChREBP epigenetically regulated COX6A2 expression by recruiting histone acetyltransferase p300 to augment histone H3 acetylation at the Cox6a2 promoter, a process inhibited by GLP-1 signaling. Given that RYGB enhances GLP-1 signaling, RYGB is likely to deactivate ChREBP by boosting GLP-1/PKA signaling, thereby reducing COX6A2 expression in islets from GK rats. These findings highlight the crucial role of the GLP-1/PKA/ChREBP axis-controlled COX6A2 in β-cell apoptosis, revealing a previously unrecognized mechanism underlying the reduction in β-cell apoptosis induced by RYGB.

Functional Classification of Fusion Proteins in Sarcoma.

Sarcomas comprise a heterogeneous group of malignant tumors of mesenchymal origin. More than 80 entities are associated with different mesenchymal lineages. Sarcomas with fibroblastic, muscle, bone, vascular, adipocytic, and other characteristics are distinguished. Nearly half of all entities contain specific chromosomal translocations that give rise to fusion proteins. These are mostly pathognomonic, and their detection by various molecular techniques supports histopathologic classification. Moreover, the fusion proteins act as oncogenic drivers, and their blockade represents a promising therapeutic approach. This review summarizes the current knowledge on fusion proteins in sarcoma. We categorize the different fusion proteins into functional classes, including kinases, epigenetic regulators, and transcription factors, and describe their mechanisms of action. Interestingly, while fusion proteins acting as transcription factors are found in all mesenchymal lineages, the others have a more restricted pattern. Most kinase-driven sarcomas belong to the fibroblastic/myofibroblastic lineage. Fusion proteins with an epigenetic function are mainly associated with sarcomas of unclear differentiation, suggesting that epigenetic dysregulation leads to a major change in cell identity. Comparison of mechanisms of action reveals recurrent functional modes, including antagonism of Polycomb activity by fusion proteins with epigenetic activity and recruitment of histone acetyltransferases by fusion transcription factors of the myogenic lineage. Finally, based on their biology, we describe potential approaches to block the activity of fusion proteins for therapeutic intervention. Overall, our work highlights differences as well as similarities in the biology of fusion proteins from different sarcomas and provides the basis for a functional classification.

Acetylation Targeting Chimera Enables Acetylation of the Tumor Suppressor p53.

With advances in chemically induced proximity technologies, heterobifunctional modalities such as proteolysis targeting chimeras (PROTACs) have been successfully advanced to clinics for treating cancer. However, pharmacologic activation of tumor-suppressor proteins for cancer treatment remains a major challenge. Here, we present a novel Acetylation Targeting Chimera (AceTAC) strategy to acetylate the p53 tumor suppressor protein. We discovered and characterized the first p53Y220C AceTAC, MS78, which recruits histone acetyltransferase p300/CBP to acetylate the p53Y220C mutant. MS78 effectively acetylated p53Y220C lysine 382 (K382) in a concentration-, time-, and p300-dependent manner and suppressed proliferation and clonogenicity of cancer cells harboring the p53Y220C mutation with little toxicity in cancer cells with wild-type p53. RNA-seq studies revealed novel p53Y220C-dependent upregulation of TRAIL apoptotic genes and downregulation of DNA damage response pathways upon acetylation induced by MS78. Altogether, the AceTAC strategy could provide a generalizable platform for targeting proteins, such as tumor suppressors, via acetylation.

#6741 TRANSCRIPTION FACTOR ATF3 EXACERBATES RENAL FIBROSIS THROUGH RECRUITING HISTONE ACETYLASES

Abstract Background and Aims Chronic kidney disease (CKD) threatens public health around the world. Renal fibrosis is a final common pathology in renal diseases of different etiologies. However, no efficient, broadly applicable anti-fibrotic therapies exist. Histone acetylation is an epigenetic modification involved in the regulation of multiple disease-specific gene expressions, balanced by histone acetyltransferases and histone deacetylase (HDAC) enzymes. Transcription factors (TF) could recruit histone-modifying enzymes and alter gene expression. But now, much remains unknown about the role of histone acetylation and whether there exits the regulator of it in fibrosis of CKD. Here, we for the first time explored a novel aspect of ATF3 promoting kidney fibrosis via recruiting the histone acetylases to fibrosis-related genes in CKD. Method We constructed a CKD mouse model by using adenine and oxonate. Serum were taken for the measurement of BUN and creatinine. Kidneys were harvested and processed for histological, sequencing, qRT-PCR, and western blotting analysis. RNA-seq and ChIP-seq (antibody: H3K27ac) of mouse kidneys were conducted for profiling the differential gene expression and H3K27ac. GO and KEGG analysis was performed for annotation of the function. Motif analysis was applied for searching the regulator of H3K27ac. Biopsy samples of patients with common CKD were used for immunohistochemical analysis. ATF3-KO mice were also conducted for defining the function of ATF3 in CKD. To profile the ATF3 binding site on chromatin, ChIP-seq of ATF3 in mice kidneys of normal control and CKD were also performed. Besides, the data contained ATF3 interact protein in databases (ChIP-atlas and BioGrid) and the results of protein interaction prediction were integrated for finding the protein-protein interaction of ATF3. TGF-β- stimulated TCMK-1 cell served as the cell model for further mechanism validation. CO-IP in cells clarifies that ATF3 could recruit the histone acetyltransferases. ChIP-qPCR of the fibrosis gene was performed to further verify the mechanism of ATF3-regulated gene expression. Results Firstly, compared with the normal control, histone modification H3K27ac repertoire was changed in chronic kidney disease. 11859 H3K27ac peaks specific to CKD, and 14996 H3K27ac peaks specific to healthy mice kidneys were found. The binding intensity of these regions has altered dramatically in the kidney of CKD. Pearson correlation analysis and function annotation showed that CKD-specific changes of H3K27ac were associated with fibrosis gene expression. Motif analysis showed that ATF3 in the top 10 TFs that may interact with H3K27ac. Among those TFs, ATF3 elicited the highest expression. Besides, ATF3 could co-localize with H3K27ac along the mice genome globally. By immunohistochemical staining analysis, we observed the upregulation of ATF3 in the kidneys of patients with biopsy-proven CKD. We found that knocking out the ATF3 could significantly reduce kidney damage in CKD mice. In parallel with improved morphological injuries, the level of kidney fibrosis gene expression was also significantly reduced in ATF3–/– mice. Furthermore, the H3K27ac on the mice chromatin altered along with the knockout of ATF3, and several fibrosis-related gene expressions which elevated in CKD were decreased by deficiency of ATF3. On the region of gene cd2, H3K27ac disappeared with the knockout of ATF3 in CKD. We found that ATF3 could interact with histone acetyltransferases (CBP, KAT7, P300) to promote the H3K27ac. Further evidenced by ChIP-qPCR of fibrosis gene cd2, we found that ATF3 could recruit the histone acetyltransferases on the fibrosis gene to promote the H3K27ac to provoke the gene expression in the cell model. Conclusion We profiled the landscape of H3K27ac in CKD, explored the epigenetic regulator of H3K27ac, and revealed that ATF3 promotes renal fibrosis in CKD. Notably, we for the first time explored a novel mechanism of ATF3 about recruiting histone acetyltransferases to regulate the H3K27ac on fibrosis gene. Our data highlighted that ATF3 might represent a potential therapeutic target against fibrotic kidney diseases.

Circ‐myh8 Promotes Pulmonary Hypertension by Recruiting KAT7 to Govern Hypoxia‐Inducible Factor‐1α Expression

Background Aberrant expression of circular RNAs (circRNAs) contributes to the initiation and progression of pulmonary hypertension (PH). Hypoxia-inducible factor (HIF) is a well-known modulator of hypoxia-induced PH. The role and underlying mechanism of circRNAs in the regulation of HIF expression remains elusive. Methods and Results We profiled pulmonary artery transcriptomes using RNA sequencing and screened circRNAs associated with hypoxia treatment. The expression of a novel circRNA, circ_chr11_67292179-67294612 (circ-myh8), was increased by hypoxia in a time-dependent manner. We evaluated the effects of circ-myh8 overexpression by adeno-associated virusor inhibition by short hairpin RNA on proliferation and cell cycling in mice and pulmonary artery smooth muscle cells. Overexpression of circ-myh8 promotes PH under normoxia, and disruption of circ-myh8 by short hairpin RNA mitigates PH in chronic hypoxic mice. Biologically, circ-myh8 induces the proliferation and cell-cycle progression of pulmonary artery smooth muscle cells in vivo and in vitro. Mechanistically, RNA pull-down and RNA immunoprecipitation assays were used to examine the interaction of circRNAs with the binding protein KAT7 (lysine acetyltransferase 7). The acetylation level of lysine 5 of histone H4 in the transcriptional initiation region of HIF1α was determined by chromatin immunoprecipitation assay followed by reverse transcription-quantitativepolymerase chain reaction. Circ-myh8 acts as a modular scaffold to recruit histone acetyltransferase KAT7 to the promoters of HIF1α, which elicits acetylation of lysine 5 of histone H4 in their promoters. Conclusions Our findings not only reveal the pivotal roles of circ-myh8 in governing histone modification in anti-PH treatment but also advocate triggering the circ-myh8/KAT7/HIF1α pathway to combat PH.

Structural mechanism of BRD4-NUT and p300 bipartite interaction in propagating aberrant gene transcription in chromatin in NUT carcinoma

BRD4-NUT, a driver fusion mutant in rare and highly aggressive NUT carcinoma, acts in aberrant transcription of anti-differentiation genes by recruiting histone acetyltransferase (HAT) p300 and promoting p300-driven histone hyperacetylation and nuclear condensation in chromatin. However, the molecular basis of how BRD4-NUT recruits and activates p300 remains elusive. Here, we report that BRD4-NUT contains two transactivation domains (TADs) in NUT that bind to the TAZ2 domain in p300. Our NMR structures reveal that NUT TADs adopt amphipathic helices when bound to the four-helical bundle TAZ2 domain. The NUT protein forms liquid-like droplets in-vitro that are enhanced by TAZ2 binding in 1:2 stoichiometry. The TAD/TAZ2 bipartite binding in BRD4-NUT/p300 triggers allosteric activation of p300 and acetylation-driven liquid-like condensation on chromatin that comprise histone H3 lysine 27 and 18 acetylation and transcription proteins BRD4L/S, CDK9, MED1, and RNA polymerase II. The BRD4-NUT/p300 chromatin condensation is key for activating transcription of pro-proliferation genes such as ALX1, resulting ALX1/Snail signaling and epithelial-to-mesenchymal transition. Our study provides a previously underappreciated structural mechanism illuminating BRD4-NUT’s bipartite p300 recruitment and activation in NUT carcinoma that nucleates a feed-forward loop for propagating histone hyperacetylation and chromatin condensation to sustain aberrant anti-differentiation gene transcription and perpetual tumor cell growth.

Transcription factor Nrf2 binds to circRNAPIBF1 to regulate SOD2 in lung adenocarcinoma progression.

Emerging evidence indicates that circular RNAs (circRNAs) play important roles in disease development, especially in cancers. Analysis of circRNA expression microarrays from the Gene Expression Omnibus database revealed that circPIBF1 was highly upregulated in lung adenocarcinoma (LUAD). The main aim of this study was to probe the function of circPIBF1 in pyroptosis of LUAD cells and the signal transduction pathways involved. CircPIBF1 was significantly overexpressed in LUAD and was related to the dismal prognosis of patients with LUAD. CircPIBF1 could bind to nuclear factor erythroid 2-related factor 2 (Nrf2), which further promoted the expression of superoxide dismutase 2 (SOD2). In addition, Nrf2 was also observed to recruit histone acetyltransferase E1A binding protein p300 (EP300) to enhance H3K27ac modification of SOD2, thus modulating the Nrf2-Keap1 signaling pathway. Moreover, we found that knockdown of circPIBF1 significantly suppressed the expression of SOD2 in cells and LUAD cell growth, while enhanced the expression of pyroptosis-related factors, which were further reversed by overexpression of SOD2 or EP300. Collectively, our findings suggest a direct involvement of circPIBF1 in pyroptosis-related LUAD carcinogenesis and implicate a role of Nrf2/EP300/SOD2 signaling in this process.

Rice EIL1 interacts with OsIAAs to regulate auxin biosynthesis mediated by the tryptophan aminotransferase MHZ10/OsTAR2 during root ethylene responses.

Ethylene plays essential roles in adaptive growth of rice (Oryza sativa). Understanding of the crosstalk between ethylene and auxin (Aux) is limited in rice. Here, from an analysis of the root-specific ethylene-insensitive rice mutant mao hu zi 10 (mhz10), we identified the tryptophan aminotransferase (TAR) MHZ10/OsTAR2, which catalyzes the key step in indole-3-pyruvic acid-dependent Aux biosynthesis. Genetically, OsTAR2 acts downstream of ethylene signaling in root ethylene responses. ETHYLENE INSENSITIVE3 like1 (OsEIL1) directly activated OsTAR2 expression. Surprisingly, ethylene induction of OsTAR2 expression still required the Aux pathway. We also show that Os indole-3-acetic acid (IAA)1/9 and OsIAA21/31 physically interact with OsEIL1 and show promotive and repressive effects on OsEIL1-activated OsTAR2 promoter activity, respectively. These effects likely depend on their EAR motif-mediated histone acetylation/deacetylation modification. The special promoting activity of OsIAA1/9 on OsEIL1 may require both the EAR motifs and the flanking sequences for recruitment of histone acetyltransferase. The repressors OsIAA21/31 exhibit earlier degradation upon ethylene treatment than the activators OsIAA1/9 in a TIR1/AFB-dependent manner, allowing OsEIL1 activation by activators OsIAA1/9 for OsTAR2 expression and signal amplification. This study reveals a positive feedback regulation of ethylene signaling by Aux biosynthesis and highlights the crosstalk between ethylene and Aux pathways at a previously underappreciated level for root growth regulation in rice.

Transcriptomic and Epigenomic Assessment Reveals Epigenetic Regulation of WRKY Genes in Response to Magnaporthe oryzae Infection in Rice.

Background: Histone acetylations acting as active hallmarks for gene transcription is involved in regulating numerous developmental and stress-responsive gene expression. Methods: The data from chromatin immunoprecipitation sequencing (ChIP-seq) was performed by using histone H3 lysine 9 acetylation (H3K9ac) antibody, and RNA sequencing (RNA-seq) utilizing rice seedlings inoculated by Magnaporthe oryzae (M. oryzae) were integrated. Results: RNA-seq data revealed that 422, 460 and 466 genes were up-regulated at 12h, 24h and 48h after inoculation. ChIP-seq data showed that 60%-80% of blast up-regulated genes at different time points were marked with H3K9ac, which was prone to be enriched in both TSS and gene body region. However, the H3K9ac level at a rather small proportion of the up-regulated genes was elevated after M. oryzae inoculation. We found that seven WRKY genes induced by rice blast fungus harbor H3K9ac. For different WRKY genes, blast fungus induction led to the increase of H3K9ac in distinct regions, including promoter, TSS or gene body, indicating that histone acetylation may play diverse roles in the activation of defense-related genes. By searching DNA-binding motifs of transcription factors in the promoter of genes with increased H3K9ac after M. oryzae infection, we found that ERF family protein-binding motifs were enriched with high -log P-value (>20), including ERF1, DEAR3, DREB2C, RAP2.6, RRTF1_3ARY, all of which contain GCC-box (GCCGCC). Conclusion: In this study, we revealed that the vast majority of genes induced by fungus M. oryzae were marked with H3K9ac preferring both TSS and gene body regions. However, H3K9ac enrichment was increased, responding to M. oryzae inoculation only at a low proportion of these genes, including several WRKY genes. Besides, for different genes, the increment of H3K9ac occurred in different regions. Finally, ERF proteins that have been proved to bind GCC-box might be one of the potential transcription factors for recruiting histone acetyltransferases to deposit histone acetylation at defense-related genes in rice.

The landscape of pioneer factor activity reveals the mechanisms of chromatin reprogramming and genome activation

Upon fertilization, embryos undergo chromatin reprogramming and genome activation; however, the mechanisms that regulate these processes are poorly understood. Here, we generated a triple mutant for Nanog, Pou5f3, and Sox19b (NPS) in zebrafish and found that NPS pioneer chromatin opening at >50% of active enhancers. NPS regulate acetylation across core histones at enhancers and promoters, and their function in gene activation can be bypassed by recruiting histone acetyltransferase to individual genes. NPS pioneer chromatin opening individually, redundantly, or additively depending on sequence context, and we show that high nucleosome occupancy facilitates NPS pioneering activity. Nucleosome position varies based on the input of different transcription factors (TFs), providing a flexible platform to modulate pioneering activity. Altogether, our results illuminate the sequence of events during genome activation and offer a conceptual framework to understand how pioneer factors interpret the genome and integrate different TF inputs across cell types and developmental transitions.

The CTCF/LncRNA-PACERR complex recruits E1A binding protein p300 to induce pro-tumour macrophages in pancreatic ductal adenocarcinoma via directly regulating PTGS2 expression.

BackgroundTumour‐associated macrophages (TAMs) play an important role in promoting the progression of pancreatic ductal adenocarcinoma (PDAC). Here, we aimed to study the epigenetic mechanisms in regulating pro‐tumour M2‐polarised TAMs in the PDAC tumour microenvironment.MethodsThis study was conducted based on ex vivo TAMs isolated from PDAC tissues and in vitro THP1‐derived TAM model. RNA‐sequencing (RNA‐seq), assay for transposase‐accessible chromatin with sequencing and chromatin immunoprecipitation sequencing were performed to investigate gene expression, chromatin accessibility, transcription factor binding sites and histone modifications. Gene knockdown in THP1‐derived TAMs was performed with lentivirus, and the impact of THP1‐derived TAMs on invasion and metastasis ability of PDAC cells were investigated with in vitro and in vivo functional assays. RNA‐chromatin interaction was analysed by chromatin isolation through RNA purification with sequencing. RNA‐protein interaction was studied by RNA immunoprecipitation and RNA pull‐down.ResultsOur data showed that the transcription factor CTCF (CCCTC‐binding factor) was highly expressed in TAMs and predicted to be significantly enriched in hyper‐accessible chromatin regions when compared to monocytes. High infiltration of CTCF+ TAMs was significantly associated with poor prognosis in PDAC patients. Knockdown of CTCF in THP1‐derived TAMs led to the down‐regulation of specific markers for M2‐polarised TAMs, including CD206 and CD163. When THP1‐derived TAMs with CTCF knockdown, they showed a decreased ability of invasion and metastasis. Further integrative analysis of multi‐omics data revealed that prostaglandin‐endoperoxide synthase 2 (PTGS2) and PTGS2 antisense NF‐κB1 complex‐mediated expression regulator RNA (PACERR) were critical downstream targets of CTCF and positively correlated with each other, which are closely situated on a chromosome. Knockdown of PACERR exhibited a similar phenotype as observed in CTCF knockdown THP1‐derived TAMs. Moreover, PACERR could directly bind to CTCF and recruit histone acetyltransferase E1A binding protein p300 to the promoter regions of PACERR and PTGS2, thereby enhancing histone acetylation and gene transcription, promoting the M2 polarization of TAMs in PDAC.ConclusionsOur study demonstrated a novel epigenetic regulation mechanism of promoting pro‐tumour M2‐polarised TAMs in the PDAC tumour microenvironment.

Brd4 is required for chondrocyte differentiation and endochondral ossification.

Differentiation of multi-potent mesenchymal stromal cells (MSCs) is directed by the activities of lineage-specific transcription factors and co-factors. A subset of these proteins controls the accessibility of chromatin by recruiting histone acetyl transferases or deacetylases that regulate acetylation of the N-termini of H3 and H4 histone proteins. Bromodomain (BRD) proteins recognize these acetylation marks and recruit the RNA pol II containing transcriptional machinery. Our previous studies have shown that Brd4 is required for osteoblast differentiation in vitro. Here, we investigated the role of Brd4 on endochondral ossification in C57BL/6 mice and chondrogenic differentiation in cell culture models. Conditional loss of Brd4 in the mesenchyme (Brd4 cKO, Brd4fl/fl: Prrx1-Cre) yields smaller mice that exhibit alteration in endochondral ossification. Importantly, abnormal growth plate morphology and delayed long bone formation is observed in juvenile Brd4 cKO mice. One week old Brd4 cKO mice have reduced proliferative and hypertrophic zones within the physis and exhibit a delay in the formation of the secondary ossification center. At the cellular level, Brd4 function is required for chondrogenic differentiation and maturation of both ATDC5 cells and immature mouse articular chondrocytes. Mechanistically, Brd4 loss suppresses Sox9 levels and reduces expression of Sox9 and Runx2 responsive endochondral genes (e.g., Col2a1, Acan, Mmp13 and Sp7/Osx). Collectively, our results indicate that Brd4 is a key epigenetic regulator required for normal chondrogenesis and endochondral ossification.

SETD2-mediated epigenetic regulation of noncanonical Wnt5A during osteoclastogenesis

To define the role of SETD2 in the WNT5a signaling in the context of osteoclastogenesis, we exploited two different models: in vitro osteoclast differentiation, and K/BxN serum-induced arthritis model. We found that SETD2 and WNT5a were upregulated during osteoclast differentiation and after induction of arthritis. Using gain- and loss-of-function approaches in the myeloid cell, we confirmed that SETD2 regulated the osteoclast markers, and WNT5a via modulating active histone marks by enriching H3K36me3, and by reducing repressive H3K27me3 mark. Additionally, during osteoclastic differentiation, the transcription of Wnt5a was also associated with the active histone H3K9 and H4K8 acetylations. Mechanistically, SETD2 directed induction of NF-κβ expression facilitated the recruitment of H3K9Ac and H4K8Ac around the TSS region of the Wnt5a gene, thereby, assisting osteoclast differentiation. Together these findings for the first time revealed that SETD2 mediated epigenetic regulation of Wnt5a plays a critical role in osteoclastogenesis and induced arthritis.Graphic abstractModel for the Role of SETD2 dependent regulation of osteoclastic differentiation. A In monocyte cells SETD2-dependent H3K36 trimethylation help to create open chromatin region along with active enhancer mark, H3K27Ac. This chromatin state facilitated the loss of a suppressive H3K27me3 mark. B Additionally, SETD2 mediated induction of NF-κβ expression leads to the recruitment of histone acetyl transferases, P300/PCAF, to the Wnt5a gene and establish H3K9Ac and H4K8Ac marks. Along with other activation marks, these acetylation marks help in Wnt5a transcription which leads to osteoclastogenesis.

ING Tumour Suppressors and ING Splice Variants as Coregulators of the Androgen Receptor Signalling in Prostate Cancer.

Prevention and overcoming castration resistance of prostate cancer (PC) remains one of the main unsolved problems in modern oncology. Hence, many studies are focused on the investigation of novel androgen receptor (AR) regulators that could serve as potential drug targets in disease therapy. Among such factors, inhibitor of growth (ING) proteins were identified. Some ING proteins act as AR transcriptional coregulators, indicating their relevance for PC research. The ING family consists of five protein-coding genes from ING1 to ING5 and pseudogene INGX. The ING genes were revealed through their sequence homology to the first identified ING1 from an in vivo screen. ING factors are a part of histone modification complexes. With the help of the conserved plant homeodomain (PHD) motif, ING factors bind to Histone 3 Lysine 4 (H3K4) methylation mark with a stronger affinity to the highest methylation grade H3K4me3 and recruit histone acetyltransferases (HAT) and histone deacetylases (HDAC) to chromatin. ING1 and ING2 are core subunits of mSIN3a-HDAC corepressor complexes, whereas ING3–5 interact with different HAT complexes that serve as coactivators. ING members belong to type II tumour suppressors and are frequently downregulated in many types of malignancies, including PC. As the family name indicates, ING proteins are able to inhibit cell growth and tumour development via regulation of cell cycle and cancer-relevant pathways such as apoptosis, cellular senescence, DNA repair, cell migration, invasion, and angiogenesis. Many ING splice variants that enhance the diversity of ING activity were discovered. However, it seems that the existence of multiple ING splice variants is underestimated, since alternative splice variants, such as the AR coregulators ING1 and ING3, counteract full-length ING and thus play an opposite functional role. These results open a novel prospective investigation direction in understanding ING factors biology in PC and other malignancies.

MAFG-AS1/MAFG positive feedback loop contributes to cisplatin resistance in bladder urothelial carcinoma through antagonistic ferroptosis

Though promoting ferroptosis can reduce cisplatin resistance in tumor cells, ferroptosis and cisplatin resistance in bladder urothelial carcinoma (BUC) following long non-coding RNAs (lncRNAs) is largely unknown. Here, we found the highly expressed lncRNA MAF transcription factor G antisense RNA 1 (MAFG-AS1) in BUC, and its inhibition increased the sensitivity of BUC cells to cisplatin by promoting ferroptosis. Mechanically, binding to iron chaperone poly(rC)-binding protein 2 (PCBP2) facilitated the recruitments of MAFG-AS1 to deubiquitinase ubiquitin carboxyl-terminal hydrolase isozyme L5 (UCHL5), thus stabilizing PCBP2 protein itself. Then PCBP2 was confirmed to interact with ferroportin 1 (FPN1), an iron export protein, leading to inhibition of ferroptosis. Moreover, the expression of MAFG-AS1 was regulated by the transcriptional factor MAFG. Interestingly, MAFG-AS1 stimulated MAFG transcription by recruiting histone acetyltransferase p300 (EP300) to promote the histone 3 at lysine 27 (H3K27ac) at genomic locus of MAFG, forming a MAFG-AS1/MAFG positive feedback loop. In patient samples, higher expression of MAFG-AS1 and MAFG in BUC tissues was significantly correlated with T status and N status, such that MAFG-AS1, MAFG, and the combination of the two were independent prognostic indicators and chemotherapy sensitivity predictive biomarkers for BUC patients. These findings suggest that inhibition of MAFG-AS1 and MAFG can increase the sensitivity of BUC cells to cisplatin through promoting ferroptosis, indicating the novel chemotherapy sensitivity biomarkers and therapeutic target for BUC.

SATB2 drives glioblastoma growth by recruiting CBP to promote FOXM1 expression in glioma stem cells

Nuclear matrix‐associated proteins (NMPs) play critical roles in regulating chromatin organization and gene transcription by binding to the matrix attachment regions (MARs) of DNA. However, the functional significance of NMPs in glioblastoma (GBM) progression remains unclear. Here, we show that the Special AT‐rich Binding Protein‐2 (SATB2), one of crucial NMPs, recruits histone acetyltransferase CBP to promote the FOXM1‐mediated cell proliferation and tumor growth of GBM. SATB2 is preferentially expressed by glioma stem cells (GSCs) in GBM. Disrupting SATB2 markedly inhibited GSC proliferation and GBM malignant growth by down‐regulating expression of key genes involved in cell proliferation program. SATB2 activates FOXM1 expression to promote GSC proliferation through binding to the MAR sequence of FOXM1 gene locus and recruiting CBP to the MAR. Importantly, pharmacological inhibition of SATB2/CBP transcriptional activity by the CBP inhibitor C646 suppressed GSC proliferation in vitro and GBM growth in vivo. Our study uncovers a crucial role of the SATB2/CBP‐mediated transcriptional regulation in GBM growth, indicating that targeting SATB2/CBP may effectively improve GBM treatment.

FosB recruits KAT5 to potentiate the growth and metastasis of papillary thyroid cancer in a DPP4-dependent manner

ObjectiveDipeptidyl peptidase IV (DPP4) has been indicated as a possible prognostic biomarker in papillary thyroid cancer (PTC). However, the mechanism of DPP4 during metastasis of PTC remains unclear. In this study, we investigated whether lysine acetyltransferase 5 (KAT5) and FBJ murine osteosarcoma viral oncogene homolog B (FosB) synergistically regulate high DPP4 expression in PTC. MethodsPTC tissues and matched paracancerous tissues were harvested, followed by the establishment of IHH-4 and TPC-1 cells with downregulation of DPP4. The relevance of DPP4 on the metastasis of PTC cells was assessed. Subsequently, the effect of KAT5 on the transcription of DPP4 was verified. The binding relationship between FosB and DPP4 was predicted by a bioinformatics website. Functional rescue experiments were performed to evaluate cell activities after overexpression of KAT5 or FosB in cells with DPP4 knockdown. ResultsDPP4 was overexpressed in PTC tissues and cell lines, which was correlated with higher risks for metastases and poorer survival. DPP4 downregulation curtailed cell growth and metastasis. Moreover, KAT5 acetylated DPP4 promoter histone, which promoted transcription activation of DPP4. Subsequently, FosB recruited KAT5 at the DPP4 promoter, thereby enhancing DPP4 transcriptional activation. Further overexpression of KAT5 or FosB in cells with low expression of DPP4 promoted cell activity. Finally, DPP4 expedited p62 nuclear translocation to elevate Keap1/Nrf2 expression, thus facilitating the growth and metastasis of PTC cells. ConclusionFosB enhanced the growth and metastasis of PTC cells by recruiting histone acetyltransferases KAT5 to increase DPP4 transcription and activate the p62/Keap1/Nrf2 signaling.

BRG1 Stimulates Endothelial Derived Alarmin MRP8 to Promote Macrophage Infiltration in an Animal Model of Cardiac Hypertrophy.

Endothelial cell derived angiocrine factors contribute to the disruption of homeostasis and the pathogenesis of cardiovascular diseases in response to stress stimuli. In the present study we investigated the role of BRG1, a key component of the chromatin remodeling complex, in the regulation of angiocrine signaling. We report that angiotensin II (Ang II) induced pathological cardiac hypertrophy was attenuated in mice with endothelial-specific ablation of BRG1 (ecKO) compared to the control mice (WT). Mitigation of cardiac hypertrophy as a result of BRG1 deficiency was accompanied by decreased macrophage homing to the hearts. This could be explained by the observation that the ecKO mice exhibited down-regulation of myeloid-related protein 8 (MRP8), a well-established chemokine for macrophages, in vascular endothelial cells compared to the WT mice. Further analysis revealed that BRG1 mediated the activation of MRP8 expression by Ang II treatment in endothelial cells to promote macrophage migration. BRG1 was recruited to the MRP8 promoter by interacting with hypoxia-inducible factor 1 (HIF-1α). Reciprocally, BRG1 facilitated the binding of HIF-1α to the MRP8 promoter by sequentially recruiting histone acetyltransferase p300 and histone demethylase KDM3A. Depletion of either p300 or KDM3A repressed the induction of MRP8 expression by Ang II and ameliorated macrophage migration. In conclusion, our data delineate a novel epigenetic pathway whereby Ang II stimulates MRP8 production and macrophage homing to promote cardiac hypertrophy.

The transcriptional corepressor CBFA2T3 inhibits all-trans-retinoic acid–induced myeloid gene expression and differentiation in acute myeloid leukemia

CBFA2/RUNX1 partner transcriptional co-repressor 3 (CBFA2T3, also known as MTG16 or ETO2) is a myeloid translocation gene family protein that functions as a master transcriptional corepressor in hematopoiesis. Recently, it has been shown that CBFA2T3 maintains leukemia stem cell gene expression and promotes relapse in acute myeloid leukemia (AML). However, a role for CBFA2T3 in myeloid differentiation of AML has not been reported. Here, we show that CBFA2T3 represses retinoic acid receptor (RAR) target gene expression and inhibits all-trans-retinoic acid (ATRA)-induced myeloid differentiation of AML cells. ChIP-Seq revealed that CBFA2T3 targets the RARα/RXRα cistrome in U937 AML cells, predominantly at myeloid-specific enhancers associated with terminal differentiation. CRISPR/Cas9-mediated abrogation of CBFA2T3 resulted in spontaneous and ATRA-induced activation of myeloid-specific genes in a manner correlated with myeloid differentiation. Importantly, these effects were reversed by CBFA2T3 re-expression. Mechanistic studies showed that CBFA2T3 inhibits RAR target gene transcription by acting at an early step to regulate histone acetyltransferase recruitment, histone acetylation, and chromatin accessibility at RARα target sites, independently of the downstream, RAR-mediated steps of transcription. Finally, we validated the inhibitory effect of CBFA2T3 on RAR in multiple AML subtypes and patient samples. To our knowledge, this is the first study to show that CBFA2T3 down-regulation is both necessary and sufficient for enhancing ATRA-induced myeloid gene expression and differentiation of AML cells. Our findings suggest that CBFA2T3 can serve as a potential target for enhancing AML responsiveness to ATRA differentiation therapies.