An iron rheostat controls hematopoietic stem cell fate.

Mechanisms governing the maintenance of blood-producing hematopoietic stem and multipotent progenitor cells (HSPCs) are incompletely understood, particularly those regulating fate, ensuring long-term maintenance, and preventing aging-associated stem cell dysfunction. We uncovered a role for transitory free cytoplasmic iron as a rheostat for adult stem cell fate control. We found that HSPCs harbor comparatively small amounts of free iron and show the activation of a conserved molecular response to limited iron-particularly during mitosis. To study the functional and molecular consequences of iron restriction, we developed models allowing for transient iron bioavailability limitation and combined single-molecule RNA quantification, metabolomics, and single-cell transcriptomic analyses with functional studies. Our data reveal that the activation of the limited iron response triggers coordinated metabolic and epigenetic events, establishing stemness-conferring gene regulation. Notably, we find that aging-associated cytoplasmic iron loading reversibly attenuates iron-dependent cell fate control, explicating intervention strategies for dysfunctional aged stem cells.

NS1-mediated enhancement of MVC transcription and replication promoted by KAT5/H4K12ac.

Histone modifications function in both cellular and viral gene expression. However, the roles of acetyltransferases and histone acetylation in parvoviral infection remain poorly understood. In the current study, we found the histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), promoted the replication and transcription of parvovirus minute virus of canines (MVC). Notably, the expression of host acetyltransferases KAT5, GTF3C4, and KAT2A was increased in MVC infection, as well as H4 acetylation (H4K12ac). KAT5 is not only responsible for H4K12ac but also crucial for viral replication and transcription. The viral nonstructural protein NS1 interacted with KAT5 and enhanced its expression. Further study showed that Y44 in KAT5, which may be tyrosine-phosphorylated, is indispensable for NS1-mediated enhancement of KAT5 and efficient MVC replication. The data demonstrated that NS1 interacted with KAT5, which resulted in an enhanced H4K12ac level to promote viral replication and transcription, implying the epigenetic addition of H4K12ac in viral chromatin-like structure by KAT5 is vital for MVC replication.IMPORTANCEParvoviral genomes are chromatinized with host histones. Therefore, histone acetylation and related acetyltransferases are required for the virus to modify histones and open densely packed chromatin structures. This study illustrated that histone acetylation status is important for MVC replication and transcription and revealed a novel mechanism that the viral nonstructural protein NS1 hijacks the host acetyltransferase KAT5 to enhance histone acetylation of H4K12ac, which relies on a potential tyrosine phosphorylation site, Y44 in KAT5. Other parvoviruses share a similar genome organization and coding potential and may adapt a similar strategy for efficient viral replication and transcription.

The Tudor-knot Domain of KAT5 Regulates Nucleosomal Substrate Acetylation.

The lysine acetyltransferase KAT5 is a pivotal enzyme responsible for catalyzing histone H4 acetylation in cells. In addition to its indispensable HAT domain, KAT5 also encompasses a conserved Tudor-knot domain at its N-terminus. However, the function of this domain remains elusive, with conflicting findings regarding its role as a histone reader. In our study, we have employed a CRISPR tiling array approach and unveiled the Tudor-knot motif as an essential domain for cell survival. The Tudor-knot domain does not bind to histone tails and is not required for KAT5's chromatin occupancy. However, its absence leads to a global reduction in histone acetylation, accompanied with genome-wide alterations in gene expression that consequently result in diminished cell viability. Mechanistically, we find that the Tudor-knot domain regulates KAT5's HAT activity on nucleosomes by fine-tuning substrate accessibility. In summary, our study uncovers the Tudor-knot motif as an essential domain for cell survival and reveals its critical role in modulating KAT5's catalytic efficiency on nucleosome and KAT5-dependent transcriptional programs critical for cell viability.

CircRHOT1 restricts gastric cancer cell ferroptosis by epigenetically regulating GPX4.

Background: Gastric cancer (GC) is a malignant form of cancer that severely threatens human health. Despite developments on treatment, the prognosis of patients with advanced GC remains poor. Hence, the identification of detailed molecular mechanisms and potential therapeutic targets is of great importance for GC study. In recent years, circular RNAs have been widely reported to be important regulators in cancer initiation and progression. This study sought to evaluate the function of circRHOT1 in GC development. Methods: Clinical specimens were collected from patients with GC to detect the level of circRHOT1. The expression of circRHOT1 in several GC cell lines was detected by quantitative real-time polymerase chain reaction. Cell Counting Kit 8 (CCK-8), colony formation, and xenograft tumor growth experiments were performed to check cell proliferation. Cell ferroptosis was determined by the levels of intracellular iron, Fe2+ (Divalent iron ion), lipid reactive oxygen species, malondialdehyde, and glutathione. The protein levels of SLC7A11 and glutathione peroxidase-4 (GPX4) were detected by western blot assays. The epigenetic regulation of the GPX4 gene was analyzed by chromatin immunoprecipitation assays. Results: CircRHOT1 was more highly expressed in the GC tumors than the adjacent non-tumor tissues. The knockdown of circRHOT1 significantly suppressed cell growth (P<0.05) and stimulated the ferroptosis of the GC cells (P<0.05). CircRHOT1 recruited KAT5 (Acetyltransferase Tip60) to promote the acetylation of lysine 27 on histone H3 protein subunit (H3k27Ac) of the GPX4 gene and stimulated gene transcription. The overexpression of KAT5 and GPX4 notably reversed the anti-proliferation effect of circRHOT1 depletion (P<0.05). Conclusions: CircRHOT1 promoted GC progression and suppressed ferroptosis by recruiting KAT5 to initiate GPX4 transcription. Our findings showed that cirRHOT1 is a promising target for GC treatment.

Epigenetic Control of Translation Checkpoint and Tumor Progression via RUVBL1-EEF1A1 Axis.

Epigenetic dysregulation is reported in multiple cancers including Ewing sarcoma (EwS). However, the epigenetic networks underlying the maintenance of oncogenic signaling and therapeutic response remain unclear. Using a series of epigenetics- and complex-focused CRISPR screens, RUVBL1, the ATPase component of NuA4 histone acetyltransferase complex, is identified to be essential for EwS tumor progression. Suppression of RUVBL1 leads to attenuated tumor growth, loss of histone H4 acetylation, and ablated MYC signaling. Mechanistically, RUVBL1 controls MYC chromatin binding and modulates the MYC-driven EEF1A1 expression and thus protein synthesis. High-density CRISPR gene body scan pinpoints the critical MYC interacting residue in RUVBL1. Finally, this study reveals the synergism between RUVBL1 suppression and pharmacological inhibition of MYC in EwS xenografts and patient-derived samples. These results indicate that the dynamic interplay between chromatin remodelers, oncogenic transcription factors, and protein translation machinery can provide novel opportunities for combination cancer therapy.

TIP60 is required for tumorigenesis in non-small cell lung cancer.

Histone modifications play crucial roles in transcriptional activation, and aberrant epigenetic changes are associated with oncogenesis. Lysine (K) acetyltransferases 5 (TIP60, also known as KAT5) is reportedly implicated in cancer development and maintenance, although its function in lung cancer remains controversial. Here we demonstrate that TIP60 knockdown in non-small cell lung cancer cell lines decreased tumor cell growth, migration, and invasion. Furthermore, analysis of a mouse lung cancer model with lung-specific conditional Tip60 knockout revealed suppressed tumor formation relative to controls, but no apparent effects on normal lung homeostasis. RNA-seq and ChIP-seq analyses of inducible TIP60 knockdown H1975 cells relative to controls revealed transglutaminase enzyme (TGM5) as downstream of TIP60. Investigation of a connectivity map database identified several candidate compounds that decrease TIP60 mRNA, one that suppressed tumor growth in cell culture and in vivo. In addition, TH1834, a TIP60 acetyltransferase inhibitor, showed comparable antitumor effects in cell culture and in vivo. Taken together, suppression of TIP60 activity shows tumor-specific efficacy against lung cancer, with no overt effect on normal tissues. Our work suggests that targeting TIP60 could be a promising approach to treating lung cancer.

VRK1 Kinase Activity Modulating Histone H4K16 Acetylation Inhibited by SIRT2 and VRK-IN-1.

The accessibility of DNA to different cellular functions requires a dynamic regulation of chromatin organization that is mediated by different epigenetic modifications, which regulate chromatin accessibility and degree of compaction. These epigenetic modifications, particularly the acetylation of histone H4 in lysine 14 (H4K16ac), determine the degree of chromatin accessibility to different nuclear functions, as well as to DNA damage drugs. H4K16ac is regulated by the balance between two alternative histone modifications, acetylation and deacetylation, which are mediated by acetylases and deacetylases. Tip60/KAT5 acetylates, and SIRT2 deacetylates histone H4K16. However, the balance between these two epigenetic enzymes is unknown. VRK1 regulates the level of H4K16 acetylation by activating Tip60. We have shown that the VRK1 and SIRT2 are able to form a stable protein complex. For this work, we used in vitro interaction, pull-down and in vitro kinase assays. In cells, their interaction and colocalization were detected by immunoprecipitation and immunofluorescence. The kinase activity of VRK1 is inhibited by a direct interaction of its N-terminal kinase domain with SIRT2 in vitro. This interaction causes a loss of H4K16ac similarly to the effect of a novel VRK1 inhibitor (VRK-IN-1) or VRK1 depletion. The use of specific SIRT2 inhibitors in lung adenocarcinoma cells induces H4K16ac, contrary to the novel VRK-IN-1 inhibitor, which prevents H4K16ac and a correct DNA damage response. Therefore, the inhibition of SIRT2 can cooperate with VRK1 in the accessibility of drugs to chromatin in response to DNA damage caused by doxorubicin.

Tip60/KAT5 Histone Acetyltransferase Is Required for Maintenance and Neurogenesis of Embryonic Neural Stem Cells.

Epigenetic regulation via epigenetic factors in collaboration with tissue-specific transcription factors is curtail for establishing functional organ systems during development. Brain development is tightly regulated by epigenetic factors, which are coordinately activated or inactivated during processes, and their dysregulation is linked to brain abnormalities and intellectual disability. However, the precise mechanism of epigenetic regulation in brain development and neurogenesis remains largely unknown. Here, we show that Tip60/KAT5 deletion in neural stem/progenitor cells (NSCs) in mice results in multiple abnormalities of brain development. Tip60-deficient embryonic brain led to microcephaly, and proliferating cells in the developing brain were reduced by Tip60 deficiency. In addition, neural differentiation and neuronal migration were severely affected in Tip60-deficient brains. Following neurogenesis in developing brains, gliogenesis started from the earlier stage of development in Tip60-deficient brains, indicating that Tip60 is involved in switching from neurogenesis to gliogenesis during brain development. It was also confirmed in vitro that poor neurosphere formation, proliferation defects, neural differentiation defects, and accelerated astrocytic differentiation in mutant NSCs are derived from Tip60-deficient embryonic brains. This study uncovers the critical role of Tip60 in brain development and NSC maintenance and function in vivo and in vitro.

Tip60-mediated H2A.Z acetylation promotes neuronal fate specification and bivalent gene activation.

Cell lineage specification is accomplished by a concerted action of chromatin remodeling and tissue-specific transcription factors. However, the mechanisms that induce and maintain appropriate lineage-specific gene expression remain elusive. Here, we used an unbiased proteomics approach to characterize chromatin regulators that mediate the induction of neuronal cell fate. We found that Tip60 acetyltransferase is essential to establish neuronal cell identity partly via acetylation of the histone variant H2A.Z. Despite its tight correlation with gene expression and active chromatin, loss of H2A.Z acetylation had little effect on chromatin accessibility or transcription. Instead, loss of Tip60 and acetyl-H2A.Z interfered with H3K4me3 deposition and activation of a unique subset of silent, lineage-restricted genes characterized by a bivalent chromatin configuration at their promoters. Altogether, our results illuminate the mechanisms underlying bivalent chromatin activation and reveal that H2A.Z acetylation regulates neuronal fate specification by establishing epigenetic competence for bivalent gene activation and cell lineage transition.

A Novel ATM Antisense Transcript ATM-AS Positively Regulates ATM Expression in Normal and Breast Cancer Cells.

OBJECTIVE: The ataxia telangiectasia mutated (ATM) gene is a master regulator in cellular DNA damage response. The dysregulation of ATM expression is frequent in breast cancer, and is known to be involved in the carcinogenesis and prognosis of cancer. However, the underlying mechanism remains unclear. The bioinformatic analysis predicted a potential antisense transcript ATM-antisense (AS) from the opposite strand of the ATM gene. The purpose of this study was to identify ATM-AS and investigate the possible effect of ATM-AS on the ATM gene regulation. METHODS: Single strand-specific RT-PCR was performed to verify the predicted antisense transcript ATM-AS within the ATM gene locus. qRT-PCR and Western blotting were used to detect the expression levels of ATM-AS and ATM in normal and breast cancer cell lines as well as in tissue samples. Luciferase reporter gene assays, biological mass spectrometry, ChIP-qPCR and RIP were used to explore the function of ATM-AS in regulating the ATM expression. Immunofluorescence and host-cell reactivation (HCR) assay were performed to evaluate the biological significance of ATM-AS in ATM-mediated DNA damage repair. Breast cancer tissue samples were used for evaluating the correlation of the ATM-AS level with the ATM expression as well as prognosis of the patients. RESULTS: The ATM-AS significantly upregulated the ATM gene activity by recruiting KAT5 histone acetyltransferase to the gene promoter. The reduced ATM-AS level led to the abnormal downregulation of ATM expression, and impaired the ATM-mediated DNA damage repair in normal breast cells in vitro. The ATM-AS level was positively correlated with the ATM expression in the examined breast cancer tissue samples, and the patient prognosis. CONCLUSION: The present study demonstrated that ATM-AS, an antisense transcript located within the ATM gene body, is an essential positive regulator of ATM expression, and functions by mediating the binding of KAT5 to the ATM promoter. These findings uncover the novel mechanism underlying the dysregulation of the ATM gene in breast cancer, and enrich our understanding of how an antisense transcript regulates its host gene.

Resveratrol Attenuate Myocardial Injury by Inhibiting Ferroptosis Via Inducing KAT5/GPX4 in Myocardial Infarction.

Myocardial infarction (MI) is a coronary artery-related disease and ranks as the leading cause of sudden death globally. Resveratrol (Res) is a bioactive component and has presented antioxidant, anti-inflammatory and anti-microbial properties. However, the effect of Res on ferroptosis during MI progression remains elusive. Here, we aimed to explore the function of Res in the regulation of ferroptosis and myocardial injury in MI. We observed that the treatment of Res attenuated the MI-related myocardium injury and fibrosis in the rats. The expression of collagen 1 and α-SMA was induced in MI rats, in which the treatment of Res could decrease the expression. Treatment of Res suppressed the levels of IL-6 and IL-1ß in MI rats. The GSH levels were inhibited and MDA, lipid ROS, and Fe2+ levels were induced in MI rats, in which the treatment of Res could reverse the phenotypes. Meanwhile, the expression of GPX4 and SLC7A11 was reduced in MI rats, while the treatment of Res could rescue the expression in the model. Meanwhile, Res relieved oxygen-glucose deprivation (OGD)-induced cardiomyocyte injury. Importantly, Res repressed OGD-induced cardiomyocyte ferroptosis in vitro. Mechanically, we identified that Res was able to enhance GPX4 expression by inducing KAT5 expression. We confirmed that KAT5 alleviated OGD-induced cardiomyocyte injury and ferroptosis. The depletion of KAT5 or GPX4 could reverse the effect of Res on OGD-induced cardiomyocyte injury. Thus, we concluded that Res attenuated myocardial injury by inhibiting ferroptosis via inducing KAT5/GPX4 in myocardial infarction. Our finding provides new evidence of the potential therapeutic effect of Res on MI by targeting ferroptosis.

Vacuolar protein sorting-associated protein 72 homolog (VPS72) binding to lysine acetyltransferase 5 (KAT5) promotes the proliferation, invasion and migration of hepatocellular carcinoma through regulating phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway.

Hepatocellular carcinoma, a fatal malignancy that occurs in the liver, poses a major public health challenge. This paper attempted to clarify the role and mechanism of vacuolar protein sorting-associated protein 72 homolog (VPS72) in the progression of hepatocellular carcinoma. Firstly, VPS72 expression in hepatocellular carcinoma tissues and the prognostic correlation were analyzed by GEPIA2 database. Western blotting and RT-qPCR assays were used to evaluate VPS72 expression in several hepatocellular carcinoma cell lines. Then, cell proliferation was assessed by cell counting kit-8 and colony formation in HuH-7 cells with VPS72 silencing. Measurement of cell invasion and migration by transwell and wound healing assays. Next, the relationship between VPS72 and lysine acetyltransferase 5 (KAT5) was predicted by bioGRID, STRING and GEIPA2 databases, which was confirmed by Co-immunoprecipitation assay. Subsequently, KAT5 was overexpressed to explore whether VPS72 could regulate the progression of hepatocellular carcinoma by binding to KAT5. And the expression of proteins related to PI3K/AKT signaling was tested with western blotting. Results indicated that VPS72 was highly expressed in hepatocellular carcinoma tissues and cell lines and was associated with poor prognosis. VPS72 knockdown inhibited the proliferation, invasion and migration of HuH-7 cells. In addition, VPS72 could bind to KAT5. KAT5 overexpression reversed the suppressive impacts of VPS72 knockdown on the proliferation, invasion and migration in HuH-7 cells. Besides, VPS72 silencing downregulated p-PI3K and p-AKT expression, which was restored by KAT5 overexpression. Collectively, VPS72 binding to KAT5 promotes the progression of hepatocellular carcinoma through the regulation of PI3K/AKT signaling pathway.

Local anesthetic levobupivacaine inhibits stemness of osteosarcoma cells by epigenetically repressing MAFB though reducing KAT5 expression.

Osteosarcoma is the most prevalent bone cancer and accounts for over half of sarcomas. In this study, we identified that the treatment of levobupivacaine suppressed proliferation of osteosarcoma cells in vitro. The tumor xenograft analysis showed that levobupivacaine significantly repressed the osteosarcoma cell growth in the nude mice. The treatment of levobupivacaine improved the apoptosis rate and attenuated invasion and migration abilities of osteosarcoma cells. The sphere formation capabilities of osteosarcoma cells were repressed by levobupivacaine. The protein levels of Sox-2, Oct3/4, and Nanog were inhibited by the treatment of levobupivacaine in osteosarcoma cells. Regarding mechanism, we identified that levobupivacaine inhibited MAFB and KAT5 expression in osteosarcoma cells. We observed that lysine acetyltransferase 5 could enriched in the promoter region of MAF BZIP transcription factor B, while levobupivacaine treatment could repressed the enrichment. The suppression of KAT5 by siRNA repressed the enrichment of histone H3 acetylation at lysine 27 and RNA polymerase II on promoter of MAFB. The expression of MAFB was decreased by KAT5 knockdown in osteosarcoma cells. The expression of MAFB was repressed by levobupivacaine, while the overexpression of KAT5 could reverse the repression of MAFB. KAT5 contributes to the cell proliferation and stemness of osteosarcoma cells. The overexpression of KAT5 or MAFB could reverse levobupivacaine-attenuated cell proliferation and stemness of osteosarcoma cells. Therefore, we concluded that local anesthetic levobupivacaine inhibited stemness of osteosarcoma cells by epigenetically repressing MAFB though reducing KAT5 expression. Levobupivacaine may act as a potential therapeutic candidate for osteosarcoma by targeting cancer stem cells.

Chromatin and transcriptomic profiling uncover dysregulation of the Tip60 HAT/HDAC2 epigenomic landscape in the neurodegenerative brain.

Disruption of histone acetylation-mediated gene control is a critical step in Alzheimer's Disease (AD), yet chromatin analysis of antagonistic histone acetyltransferases (HATs) and histone deacetylases (HDACs) causing these alterations remains uncharacterized. We report the first Tip60 HAT versus HDAC2 chromatin (ChIP-seq) and transcriptional (RNA-seq) profiling study in Drosophila melanogaster brains that model early human AD. We find Tip60 and HDAC2 predominantly recruited to identical neuronal genes. Moreover, AD brains exhibit robust genome-wide early alterations that include enhanced HDAC2 and reduced Tip60 binding and transcriptional dysregulation. Orthologous human genes to co-Tip60/HDAC2 D. melanogaster neural targets exhibit conserved disruption patterns in AD patient hippocampi. Notably, we discovered distinct transcription factor binding sites close or within Tip60/HDAC2 co-peaks in neuronal genes, implicating them in coenzyme recruitment. Increased Tip60 protects against transcriptional dysregulation and enhanced HDAC2 enrichment genome-wide. We advocate Tip60 HAT/HDAC2 mediated epigenetic neuronal gene disruption as a genome-wide initial causal event in AD.

The Acetyltransferase KAT5 Inhibitor NU 9056 Promotes Apoptosis and Inhibits JAK2/STAT3 Pathway in Extranodal NK/T Cell Lymphoma.

BACKGROUND: Extranodal natural killer/T cell lymphoma (ENKTL) is an aggressive malignant non- Hodgkin's lymphoma (NHL) with a poor prognosis. Therefore, novel therapeutic biomarkers and agents must be identified for the same. KAT5 inhibitor, NU 9056, is a small molecule that can inhibit cellular proliferation; however, its role in ENKTL has not been studied. OBJECTIVE: The present study investigated the effect of NU 9056 in ENKTL cells and explored the possible molecular mechanism for its antitumour effect. METHODS: The role of NU 9056 in ENKTL cells was investigated through the Cell Counting Kit-8 assay, flow cytometry, Western blot, and real-time quantitative polymerase chain reaction assay. RESULTS: NU 9056 inhibited ENKTL cell proliferation and induced G2/M phase arrest. NU 9056 also induced apoptosis by upregulating DR4, DR5, and caspase 8 expressions. Additionally, NU 9056 increased the expression of Bax, Bid, and cytochrome C and decreased the expression of Bcl-2, Mcl-1, and XIAP. Furthermore, NU 9056 activated endoplasmic reticulum (ER) stress and inhibited the JAK2/STAT3 signalling pathway. The p38 mitogen-activated protein kinase (MAPK) signalling pathway was also activated by NU 9056, and the ERK signalling pathway was suppressed in natural killer/T cell lymphoma cells. CONCLUSION: NU 9056 inhibited cell proliferation, arrested cell cycle in the G2/M phase, and induced apoptosis through the stimulation of ER stress, thus inhibiting the JAK2/STAT3 signalling pathway and regulating MAPK pathways in ENKTL cells.

Lysine Acetyltransferase 5 and Tumor / 中国生物化学与分子生物学报

Lysine acetyltransferase 5 (KAT5), a member of the MYST family, can participate in cellular processes such as transcription, DNA repair, differentiation and signal transduction by acetylating different substrates. The role of KAT5 cannot be replaced by other MYST family members, and the knockout of KAT5 can directly lead to apoptosis, indicating that KAT5 may be located in the upstream of physiological signaling pathways in cells and play an extremely important and unique role. Therefore, the changes in KAT5 expression are very likely to lead to the occurrence and development of tumors. Previous studies have found that KAT5 is downregulated in breast cancer, melanoma, and lung cancer, and is considered a tumor suppressor in these tumors. However, in recent years, studies have found that KAT5 can be either highly or lowly expressed in breast cancer, liver cancer, melanoma, prostate cancer, lung cancer and other tumors. On the premise of high KAT5 expression, KAT5 can play a tumor-promoting role. While on the premise of low KAT5 expression, KAT5 can also play as a tumor suppressor. With further decrease of KAT5 expression, its tumor suppressive effect is weakened, which may lead to the occurrence and development of tumors. In addition, KAT5 has also been found to be differentially expressed in osteosarcoma, thyroid cancer, glioblastoma, colorectal cancer and other tumors, and the differential expression of KAT5 is closely related to the proliferation, metastasis, apoptosis, drug and radiotherapy resistance of tumor cells. Therefore, KAT5 is one of the potential tumor therapeutic targets. Here, we summarize the expression of KAT5 in tumors and the tumor-suppressing or tumor-promoting signaling pathways involved in the corresponding expression in recent years, hoping to provide new inspiration and reference for tumor treatment and prognosis monitoring.

Ketamine suppresses proliferation and induces ferroptosis and apoptosis of breast cancer cells by targeting KAT5/GPX4 axis.

Breast cancer (BC) serves as a prevalent and mortal malignancy among female globally. Ferroptosis, as an oxidative cell death that characterized by abnormal iron accumulation, plays critical role in cancer development. Ketamine is a rapid-acting anesthetic agent and has presented potential anti-tumor properties. However, the effect of Ketamine on breast cancer is still obscure. Here, we aimed to explore the function of Ketamine in the modulation of proliferation and ferroptosis of breast cancer cells. The cell viability of breast cancer cells was repressed by the treatment of Ketamine, while ferroptosis inhibitor ferrostatin 1 and apoptosis inhibitor ZVAD-FMK could restore the cell viability. The treatment of Ketamine significantly decreased the Edu-positive breast cancer cells and the colony formation numbers, and the treatment of ferrostatin 1 reversed the effect of Ketamine. We observed that the levels of ferroptosis markers, such as MDA, lipid ROS, and Fe2+ were increased by the treatment of Ketamine in breast cancer cells. Regarding to the mechanism, we found that Ketamine inhibited the expression of GPX4, an anti-ferroptosis factor, by attenuating KAT5 on the promoter region of GPX4, repressing the enrichment of histone H3 lysine 27 acetylation (H3K27ac) and RNA polymerase II (RNA pol II). The treatment of Ketamine reduced the cell viability and proliferation of breast cancer cells, in which the overexpression of KAT5 or GPX4 was able to restore the phenotypes. The treatment of Ketamine induced the levels of MDA, lipid ROS, and Fe2+, while KAT5 or GPX4 overexpression could reverse this effect in breast cancer cells. Thus, we concluded that Ketamine suppressed proliferation and induced ferroptosis of breast cancer cells by targeting KAT5/GPX4 axis. Ketamine may serve as a potential therapeutic strategy for breast cancer.

Circular RNA circRHOT1 contributes to pathogenesis of non-small cell lung cancer by epigenetically enhancing C-MYC expression through recruiting KAT5.

Non-small cell lung cancer (NSCLC) one of the most prevalent and severe malignancies globally and the molecular mechanisms of NSCLC are poor understood, limiting the development of diagnostic biomarkers and targeted therapies. Circular RNAs (circRNAs) have been identified as a sort of critical regulator in cancer progression. In this study, we identities the epigenetic regulation function of circular RNA circRHOT1 in promoting NSCLC cell proliferation. We found that circRHOT1 were elevated in the clinical tumor tissues relative to that in the peritumor tissues from NSCLC patients. circRHOT1 was up-regulated in human lung cancer cell lines compared with normal human lung epithelial cell line. MTT assays revealed that the silencing of circRHOT1 by siRNA suppressed cell viabilities of NSCLC cells. Colony formation and Edu assays confirmed that circRHOT1 knockdown attenuated NSCLC cell proliferation in vitro. Meanwhile, the depletion of circRHOT1 induced NSCLC cell apoptosis and cell cycle arrest in vitro. Mechanically, the depletion of circRHOT1 remarkably reduced c-MYC mRNA and protein expression in NSCLC cells. Inhibition of circRHOT1 reduced the enrichment of transcription active marker histone H3 lysine 27 acetylation (H3K27ac) and RNA polymerase II on the promoter of c-MYC. RNA pull down analysis showed that circRHOT1 was able to directly interact with acetyltransferase KAT5 in NSCLC cells. In summary, we concluded that circRHOT1 contributed to pathogenesis of NSCLC by epigenetically enhancing c-MYC expression through recruiting KAT5. CircRHOT1 and KAT5 may be used as the potential targets for NSCLC therapy.

Choline kinase alpha 2 acts as a protein kinase to promote lipolysis of lipid droplets.

Lipid droplets are important for cancer cell growth and survival. However, the mechanism underlying the initiation of lipid droplet lipolysis is not well understood. We demonstrate here that glucose deprivation induces the binding of choline kinase (CHK) α2 to lipid droplets, which is sequentially mediated by AMPK-dependent CHKα2 S279 phosphorylation and KAT5-dependent CHKα2 K247 acetylation. Importantly, CHKα2 with altered catalytic domain conformation functions as a protein kinase and phosphorylates PLIN2 at Y232 and PLIN3 at Y251. The phosphorylated PLIN2/3 dissociate from lipid droplets and are degraded by Hsc70-mediated autophagy, thereby promoting lipid droplet lipolysis, fatty acid oxidation, and brain tumor growth. In addition, levels of CHKα2 S279 phosphorylation, CHKα2 K247 acetylation, and PLIN2/3 phosphorylation are positively correlated with one another in human glioblastoma specimens and are associated with poor prognosis in glioblastoma patients. These findings underscore the role of CHKα2 as a protein kinase in lipolysis and glioblastoma development.

Schizosaccharomyces pombe KAT5 contributes to resection and repair of a DNA double-strand break.

Chromatin remodeling is essential for effective repair of a DNA double-strand break (DSB). KAT5 (Schizosaccharomyces pombe Mst1, human TIP60) is a MYST family histone acetyltransferase conserved from yeast to humans that coordinates various DNA damage response activities at a DNA DSB, including histone remodeling and activation of the DNA damage checkpoint. In S. pombe, mutations in mst1+ causes sensitivity to DNA damaging drugs. Here we show that Mst1 is recruited to DSBs. Mutation of mst1+ disrupts recruitment of repair proteins and delays resection. These defects are partially rescued by deletion of pku70, which has been previously shown to antagonize repair by homologous recombination (HR). These phenotypes of mst1 are similar to pht1-4KR, a nonacetylatable form of histone variant H2A.Z, which has been proposed to affect resection. Our data suggest that Mst1 functions to direct repair of DSBs toward HR pathways by modulating resection at the DSB.