HBO1 is required for H3K14 acetylation and normal transcriptional activity during embryonic development

KAT7 serves as an oncogenic gene and regulates CCL3 expression via STAT1 signaling in osteosarcoma

Osteosarcoma, considered as the primary cause of malignant bone tumors in children, necessitates novel therapeutic strategies to enhance overall survival rates. KAT7, a histone acetyltransferase, exerts pivotal functions in gene transcription and immune modulation. In light of this, our study identified a significant upregulation of KAT7 in the mRNA and protein levels in human osteosarcoma, boosting cell proliferation in vivo and in vitro. In addition, KAT7-mediated H3K14ac activation induced MMP14 transcription, leading to increased expression and facilitation of osteosarcoma cell metastasis. Subsequent bioinformatics analyses highlighted a correlation between KAT7 and adaptive immune responses, indicating CCL3 as a downstream target of KAT7. Mechanistically, STAT1 was found to transcriptionally upregulate CCL3 expression. Furthermore, overexpression of KAT7 suppressed CCL3 secretions, whereas knockdown of KAT7 enhanced its release. Overall, these findings underscore the oncogenic role of KAT7 in regulating immune responses for osteosarcoma treatment.

KAT7 suppresses tumorigenesis in clear cell renal cell carcinoma (ccRCC) by regulating cell cycle and ferroptosis sensitivity

Clear cell renal cell carcinoma (ccRCC) is one of the most aggressive malignancies in the urological system, known for its high immunogenicity. However, its pathogenesis remains unclear. This study utilized bioinformatics algorithms and in vitro experiments to investigate the role of KAT7 in ccRCC. The results indicate that KAT7 is significantly downregulated in ccRCC tissues and cell lines, which is linked to distant metastasis and unfavorable outcomes in ccRCC patients. Overexpression of KAT7 in vitro notably decreased the proliferation, migration, and invasion of renal cancer cells and inhibited Epithelial-Mesenchymal Transition (EMT). Additionally, Gene Set Enrichment Analysis (GSEA) demonstrated that KAT7-related gene functions are associated with cell cycle and ferroptosis transcription factors. Treatment with a KAT7 acetylation inhibitor in ccRCC cell lines reversed the S phase arrest caused by KAT7 overexpression. Similarly, ferroptosis inhibitors alleviated ferroptosis induced by overexpressed KAT7. In conclusion, the findings suggest that KAT7 acts as a tumor suppressor in ccRCC by modulating the cell cycle and ferroptosis sensitivity, underscoring its potential as a therapeutic target and prognostic biomarker for renal cell carcinoma patients.

Guiding the HBO1 complex function through the JADE subunit

JADE is a core subunit of the HBO1 acetyltransferase complex that regulates developmental and epigenetic programs and promotes gene transcription. Here we describe the mechanism by which JADE facilitates recruitment of the HBO1 complex to chromatin and mediates its enzymatic activity. Structural, genomic and complex assembly in vivo studies show that the PZP (PHD1-zinc-knuckle-PHD2) domain of JADE engages the nucleosome through binding to histone H3 and DNA and is necessary for the association with chromatin targets. Recognition of unmethylated H3K4 by PZP directs enzymatic activity of the complex toward histone H4 acetylation, whereas H3K4 hypermethylation alters histone substrate selectivity. We demonstrate that PZP contributes to leukemogenesis, augmenting transforming activity of the NUP98-JADE2 fusion. Our findings highlight biological consequences and the impact of the intact JADE subunit on genomic recruitment, enzymatic function and pathological activity of the HBO1 complex.

Epigenetic signatures of trophoblast lineage and their biological functions

Trophoblasts play a crucial role in embryo implantation and in interacting with the maternal uterus. The trophoblast lineage develops into a substantial part of the placenta, a temporary extra-embryonic organ, capable of undergoing distinctive epigenetic events during development. The critical role of trophoblast-specific epigenetic signatures in regulating placental development has become known, significantly advancing our understanding of trophoblast identity and lineage development. Scientific efforts are revealing how trophoblast-specific epigenetic signatures mediate stage-specific gene regulatory programming during the development of the trophoblast lineage. These epigenetic signatures have a significant impact on blastocyst formation, placental development, as well as the growth and survival of embryos and fetuses. In evolution, DNA hypomethylation in the trophoblast lineage is conserved, and there is a significant disparity in the control of epigenetic dynamics and the landscape of genomic imprinting. Scientists have used murine and human multipotent trophoblast cells as in vitro models to recapitulate the essential epigenetic processes of placental development. Here, we review the epigenetic signatures of the trophoblast lineage and their biological functions to enhance our understanding of placental evolution, development, and function.

HBO1, a MYSTerious KAT and its links to cancer

The histone acetyltransferase HBO1, also known as KAT7, is a major chromatin modifying enzyme responsible for H3 and H4 acetylation. It is found within two distinct tetrameric complexes, the JADE subunit-containing complex and BRPF subunit-containing complex. The HBO1-JADE complex acetylates lysine 5, 8 and 12 of histone H4, and the HBO1-BRPF complex acetylates lysine 14 of histone H3. HBO1 regulates gene transcription, DNA replication, DNA damage repair, and centromere function. It is involved in diverse signaling pathways and plays crucial roles in development and stem cell biology. Recent work has established a strong relationship of HBO1 with the histone methyltransferase MLL/KMT2A in acute myeloid leukemia. Here, we discuss functional and pathological links of HBO1 to cancer, highlighting the underlying mechanisms that may pave the way to the development of novel anti-cancer therapies.

KAT7 enhances the proliferation and metastasis of head and neck squamous carcinoma by promoting the acetylation level of LDHA

Lysine acetyltransferase 7 (KAT7), a histone acetyltransferase, has recently been identified as an oncoprotein and has been implicated in the development of various malignancies. However, its specific role in head and neck squamous carcinoma (HNSCC) has not been fully elucidated. Our study revealed that high expression of KAT7 in HNSCC patients is associated with poor survival prognosis and silencing KAT7 inhibits the Warburg effect, leading to reduced proliferation, invasion, and metastatic potential of HNSCC. Further investigation uncovered a link between the high expression of KAT7 in HNSCC and tumor-specific glycolytic metabolism. Notably, KAT7 positively regulates Lactate dehydrogenase A (LDHA), a key enzyme in metabolism, to promote lactate production and create a conducive environment for tumor proliferation and metastasis. Additionally, KAT7 enhances LDHA activity and upregulates LDHA protein expression by acetylating the lysine 118 site of LDHA. Treatment with WM3835, a KAT7 inhibitor, effectively suppressed the growth of subcutaneously implanted HNSCC cells in mice. In conclusion, our findings suggest that KAT7 exerts pro-cancer effects in HNSCC by acetylating LDHA and may serve as a potential therapeutic target. Inhibiting KAT7 or LDHA expression holds promise as a therapeutic strategy to suppress the growth and progression of HNSCC.

HBO1 determines SMAD action in pluripotency and mesendoderm specification

TGF-β signaling family plays an essential role to regulate fate decisions in pluripotency and lineage specification. How the action of TGF-β family signaling is intrinsically executed remains not fully elucidated. Here, we show that HBO1, a MYST histone acetyltransferase (HAT) is an essential cell intrinsic determinant for TGF-β signaling in human embryonic stem cells (hESCs). HBO1-/- hESCs fail to response to TGF-β signaling to maintain pluripotency and spontaneously differentiate into neuroectoderm. Moreover, HBO1 deficient hESCs show complete defect in mesendoderm specification in BMP4-triggered gastruloids or teratomas. Molecularly, HBO1 interacts with SMAD4 and co-binds the open chromatin labeled by H3K14ac and H3K4me3 in undifferentiated hESCs. Upon differentiation, HBO1/SMAD4 co-bind and maintain the mesoderm genes in BMP4-triggered mesoderm cells while lose chromatin occupancy in neural cells induced by dual-SMAD inhibition. Our data reveal an essential role of HBO1, a chromatin factor to determine the action of SMAD in both human pluripotency and mesendoderm specification.

HBO1/KAT7/MYST2 HAT complex regulates human adenovirus replicative cycle

Human adenoviruses (HAdV) belong to a small DNA tumor virus family that continues as valuable models in understanding the viral strategies of usurping cell growth regulation. A number of HAdV type 2/5 early viral gene products interact with a variety of cellular proteins to build a conducive environment that promotes viral replication. Here we show that HBO1 (Histone Acetyltransferase Binding to ORC1), a member of the MYST histone acetyltransferase (HAT) complex (also known as KAT7 and MYST2) that acetylates most of the histone H3 lysine 14, is essential for HAdV5 growth. HBO1/MYST2/KAT7 HAT complexes are critical for a variety of cellular processes including control of cell proliferation. In HBO1 downregulated human cells, HAdV5 infection results in reduced expression of E1A and other viral early genes, virus growth is also reduced significantly. Importantly, HBO1 downregulation reduced H3 lysine 14 acetylation at viral promoters during productive infection, likely driving reduced viral gene expression. HBO1 was also associated with viral promoters during infection and co-localized with viral replication centers in the nuclei of infected cells. In transiently transfected cells, overexpression of E1A along with HBO1 stimulated histone acetyltransferase activity of HBO1. E1A also co-immunoprecipitated with HBO1 in transiently transfected cells. In summary, our results demonstrate that HAdV recruits the HBO1 HAT complex to aid in viral replication.

The histone acetyltransferase KAT6B is required for hematopoietic stem cell development and function

The histone lysine acetyltransferase KAT6B (MYST4, MORF, QKF) is the target of recurrent chromosomal translocations causing hematological malignancies with poor prognosis. Using Kat6b germline deletion and overexpression in mice, we determined the role of KAT6B in the hematopoietic system. We found that KAT6B sustained the fetal hematopoietic stem cell pool but did not affect viability or differentiation. KAT6B was essential for normal levels of histone H3 lysine 9 (H3K9) acetylation but not for a previously proposed target, H3K23. Compound heterozygosity of Kat6b and the closely related gene, Kat6a, abolished hematopoietic reconstitution after transplantation. KAT6B and KAT6A cooperatively promoted transcription of genes regulating hematopoiesis, including the Hoxa cluster, Pbx1, Meis1, Gata family, Erg, and Flt3. In conclusion, we identified the hematopoietic processes requiring Kat6b and showed that KAT6B and KAT6A synergistically promoted HSC development, function, and transcription. Our findings are pertinent to current clinical trials testing KAT6A/B inhibitors as cancer therapeutics.

Increasing histone acetylation improves sociability and restores learning and memory in KAT6B-haploinsufficient mice

Mutations in genes encoding chromatin modifiers are enriched among mutations causing intellectual disability. The continuing development of the brain postnatally, coupled with the inherent reversibility of chromatin modifications, may afford an opportunity for therapeutic intervention following a genetic diagnosis. Development of treatments requires an understanding of protein function and models of the disease. Here, we provide a mouse model of Say-Barber-Biesecker-Young-Simpson syndrome (SBBYSS) (OMIM 603736) and demonstrate proof-of-principle efficacy of postnatal treatment. SBBYSS results from heterozygous mutations in the KAT6B (MYST4/MORF/QFK) gene and is characterized by intellectual disability and autism-like behaviors. Using human cells carrying SBBYSS-specific KAT6B mutations and Kat6b heterozygous mice (Kat6b+/-), we showed that KAT6B deficiency caused a reduction in histone H3 lysine 9 acetylation. Kat6b+/- mice displayed learning, memory, and social deficits, mirroring SBBYSS individuals. Treatment with a histone deacetylase inhibitor, valproic acid, or an acetyl donor, acetyl-carnitine (ALCAR), elevated histone acetylation levels in the human cells with SBBYSS mutations and in brain and blood cells of Kat6b+/- mice and partially reversed gene expression changes in Kat6b+/- cortical neurons. Both compounds improved sociability in Kat6b+/- mice, and ALCAR treatment restored learning and memory. These data suggest that a subset of SBBYSS individuals may benefit from postnatal therapeutic interventions.

Genome-wide CRISPR activation screen identifies JADE3 as an antiviral activator of NF-kB-dependent IFITM3 expression

The innate immune system features a web of interacting pathways that require exquisite regulation. To identify novel nodes in this immune landscape, we conducted a gain-of-function, genome-wide CRISPR activation screen with influenza A virus. We identified both appreciated and novel antiviral genes, including Jade family PHD zinc finger 3 (JADE3) a protein involved in directing the histone acetyltransferase histone acetyltransferase binding to ORC1 complex to modify chromatin and regulate transcription. JADE3 is both necessary and sufficient to restrict influenza A virus infection. Our results suggest a distinct function for JADE3 as expression of the closely related paralogs JADE1 and JADE2 does not confer resistance to influenza A virus infection. JADE3 is required for both constitutive and inducible expression of the well-characterized antiviral gene interferon-induced transmembrane protein 3 (IFITM3). Furthermore, we find JADE3 activates the NF-kB signaling pathway, which is required for the promotion of IFITM3 expression by JADE3. Therefore, we propose JADE3 activates an antiviral genetic program involving NF-kB-dependent IFITM3 expression to restrict influenza A virus infection.

Discovery of a highly potent, selective, orally bioavailable inhibitor of KAT6A/B histone acetyltransferases with efficacy against KAT6A-high ER+ breast cancer

KAT6A, and its paralog KAT6B, are histone lysine acetyltransferases (HAT) that acetylate histone H3K23 and exert an oncogenic role in several tumor types including breast cancer where KAT6A is frequently amplified/overexpressed. However, pharmacologic targeting of KAT6A to achieve therapeutic benefit has been a challenge. Here we describe identification of a highly potent, selective, and orally bioavailable KAT6A/KAT6B inhibitor CTx-648 (PF-9363), derived from a benzisoxazole series, which demonstrates anti-tumor activity in correlation with H3K23Ac inhibition in KAT6A over-expressing breast cancer. Transcriptional and epigenetic profiling studies show reduced RNA Pol II binding and downregulation of genes involved in estrogen signaling, cell cycle, Myc and stem cell pathways associated with CTx-648 anti-tumor activity in ER-positive (ER+) breast cancer. CTx-648 treatment leads to potent tumor growth inhibition in ER+ breast cancer in vivo models, including models refractory to endocrine therapy, highlighting the potential for targeting KAT6A in ER+ breast cancer.

Genome-wide CRISPR activation screen identifies JADE3 as an antiviral activator of NF-kB

The innate immune system features a web of interacting pathways that require exquisite regulation. To identify novel nodes in this immune landscape we conducted a gain of function, genome-wide CRISPR activation screen with influenza A virus. We identified both appreciated and novel antiviral genes, including JADE3 a protein involved in directing the histone acetyltransferase HBO1 complex to modify chromatin and regulate transcription. JADE3 is both necessary and sufficient to restrict influenza A virus infection. Interestingly, expression of the closely related paralogues JADE1 and JADE2 are unable to restrict influenza A virus infection, suggesting a distinct function of JADE3. We identify both shared and unique transcriptional signatures between uninfected cells expressing JADE3 and JADE2. These data provide a framework for understanding the overlapping and distinct functions of the JADE family of paralogues. Specifically, we find that JADE3 expression activates the NF-kB signaling pathway, consistent with an antiviral function. Therefore, we propose JADE3, but not JADE1 or JADE2, activates an antiviral genetic program involving the NF-kB pathway to restrict influenza A virus infection.

Histone acetylation by HBO1 (KAT7) activates Wnt/β-catenin signaling to promote leukemogenesis in B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia (B-ALL) is an aggressive hematological disorder with a dismal prognosis. The dysregulation of histone acetylation is of great significance in the pathogenesis and progression of B-ALL. Regarded as a fundamental acetyltransferase gene, the role of HBO1 (lysine acetyltransferase 7/KAT7) in B-ALL has not been investigated. Herein, we found that HBO1 expression was elevated in human B-ALL cells and associated with poor disease-free survival. Strikingly, HBO1 knockdown inhibited viability, proliferation, and G1-S cycle progression in B-ALL cells, while provoking apoptosis. In contrast, ectopic overexpression of HBO1 enhanced cell viability and proliferation but inhibited apoptotic activation. The results of in vivo experiments also certificated the inhibitory effect of HBO1 knockdown on tumor growth. Mechanistically, HBO1 acetylated histone H3K14, H4K8, and H4K12, followed by upregulating CTNNB1 expression, resulting in activation of the Wnt/β-catenin signaling pathway. Moreover, a novel small molecule inhibitor of HBO1, WM-3835, potently inhibited the progression of B-ALL. Our data identified HBO1 as an efficacious regulator of CTNNB1 with therapeutic potential in B-ALL.

Stability selection enhances feature selection and enables accurate prediction of gestational age using only five DNA methylation sites

BACKGROUND

DNA methylation (DNAm) is robustly associated with chronological age in children and adults, and gestational age (GA) in newborns. This property has enabled the development of several epigenetic clocks that can accurately predict chronological age and GA. However, the lack of overlap in predictive CpGs across different epigenetic clocks remains elusive. Our main aim was therefore to identify and characterize CpGs that are stably predictive of GA.

RESULTS

We applied a statistical approach called 'stability selection' to DNAm data from 2138 newborns in the Norwegian Mother, Father, and Child Cohort study. Stability selection combines subsampling with variable selection to restrict the number of false discoveries in the set of selected variables. Twenty-four CpGs were identified as being stably predictive of GA. Intriguingly, only up to 10% of the CpGs in previous GA clocks were found to be stably selected. Based on these results, we used generalized additive model regression to develop a new GA clock consisting of only five CpGs, which showed a similar predictive performance as previous GA clocks (R2 = 0.674, median absolute deviation = 4.4 days). These CpGs were in or near genes and regulatory regions involved in immune responses, metabolism, and developmental processes. Furthermore, accounting for nonlinear associations improved prediction performance in preterm newborns.

CONCLUSION

We present a methodological framework for feature selection that is broadly applicable to any trait that can be predicted from DNAm data. We demonstrate its utility by identifying CpGs that are highly predictive of GA and present a new and highly performant GA clock based on only five CpGs that is more amenable to a clinical setting.

The chromatin reader protein ING5 is required for normal hematopoietic cell numbers in the fetal liver

ING5 is a component of KAT6A and KAT7 histone lysine acetylation protein complexes. ING5 contains a PHD domain that binds to histone H3 lysine 4 when it is trimethylated, and so functions as a 'reader' and adaptor protein. KAT6A and KAT7 function are critical for normal hematopoiesis. To examine the function of ING5 in hematopoiesis, we generated a null allele of Ing5. Mice lacking ING5 during development had decreased foetal liver cellularity, decreased numbers of hematopoietic stem cells and perturbed erythropoiesis compared to wild-type control mice. Ing5^-/- pups had hypoplastic spleens. Competitive transplantation experiments using foetal liver hematopoietic cells showed that there was no defect in long-term repopulating capacity of stem cells lacking ING5, suggesting that the defects during the foetal stage were not cell intrinsic. Together, these results suggest that ING5 function is dispensable for normal hematopoiesis but may be required for timely foetal hematopoiesis in a cell-extrinsic manner.

KAT7 promotes radioresistance through upregulating PI3K/AKT signaling in breast cancer

Chromatin-modifying enzymes are commonly altered in cancers, but the molecular mechanism by which they regulate cancers remains poorly understood. Herein, we demonstrated that Lysine acetyltransferase 7 (KAT7) was upregulated in breast cancer. KAT7 expression negatively correlated with the survival of breast cancer patients, and KAT7 silencing suppressed breast cancer radioresistance in vitro. Mechanistically, KAT7 activated Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) transcription, leading to enhanced PI3K/AKT signaling and radioresistance. Overexpression of AKT or PIK3CA restored radioresistance suppression induced by KAT7 inhibition. Moreover, overexpression of KAT7, but not KAT7 acetyltransferase activity-deficient mutants promoted AKT phosphorylation at the Ser473 site, PIK3CA expression and radioresistance suppression due to KAT7 inhibition. In conclusion, KAT7 has huge prospects for clinical application as a new target for predicting radioresistance in breast cancer patients.

Stem cell plasticity, acetylation of H3K14, and de novo gene activation rely on KAT7

In the conventional model of transcriptional activation, transcription factors bind to response elements and recruit co-factors, including histone acetyltransferases. Contrary to this model, we show that the histone acetyltransferase KAT7 (HBO1/MYST2) is required genome wide for histone H3 lysine 14 acetylation (H3K14ac). Examining neural stem cells, we find that KAT7 and H3K14ac are present not only at transcribed genes but also at inactive genes, intergenic regions, and in heterochromatin. KAT7 and H3K14ac were not required for the continued transcription of genes that were actively transcribed at the time of loss of KAT7 but indispensable for the activation of repressed genes. The absence of KAT7 abrogates neural stem cell plasticity, diverse differentiation pathways, and cerebral cortex development. Re-expression of KAT7 restored stem cell developmental potential. Overexpression of KAT7 enhanced neuron and oligodendrocyte differentiation. Our data suggest that KAT7 prepares chromatin for transcriptional activation and is a prerequisite for gene activation.

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.

The MOZ-BRPF1 acetyltransferase complex in epigenetic crosstalk linked to gene regulation, development, and human diseases

Acetylation of lysine residues on histone tails is an important post-translational modification (PTM) that regulates chromatin dynamics to allow gene transcription as well as DNA replication and repair. Histone acetyltransferases (HATs) are often found in large multi-subunit complexes and can also modify specific lysine residues in non-histone substrates. Interestingly, the presence of various histone PTM recognizing domains (reader domains) in these complexes ensures their specific localization, enabling the epigenetic crosstalk and context-specific activity. In this review, we will cover the biochemical and functional properties of the MOZ-BRPF1 acetyltransferase complex, underlining its role in normal biological processes as well as in disease progression. We will discuss how epigenetic reader domains within the MOZ-BRPF1 complex affect its chromatin localization and the histone acetyltransferase specificity of the complex. We will also summarize how MOZ-BRPF1 is linked to development via controlling cell stemness and how mutations or changes in expression levels of MOZ/BRPF1 can lead to developmental disorders or cancer. As a last touch, we will review the latest drug candidates for these two proteins and discuss the therapeutic possibilities.

The role of altered protein acetylation in neurodegenerative disease

Acetylation is a key post-translational modification (PTM) involved in the regulation of both histone and non-histone proteins. It controls cellular processes such as DNA transcription, RNA modifications, proteostasis, aging, autophagy, regulation of cytoskeletal structures, and metabolism. Acetylation is essential to maintain neuronal plasticity and therefore essential for memory and learning. Homeostasis of acetylation is maintained through the activities of histone acetyltransferases (HAT) and histone deacetylase (HDAC) enzymes, with alterations to these tightly regulated processes reported in several neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). Both hyperacetylation and hypoacetylation can impair neuronal physiological homeostasis and increase the accumulation of pathophysiological proteins such as tau, α-synuclein, and Huntingtin protein implicated in AD, PD, and HD, respectively. Additionally, dysregulation of acetylation is linked to impaired axonal transport, a key pathological mechanism in ALS. This review article will discuss the physiological roles of protein acetylation and examine the current literature that describes altered protein acetylation in neurodegenerative disorders.

The multiple facets of acetyl-CoA metabolism: Energetics, biosynthesis, regulation, acylation and inborn errors

Acetyl-coenzyme A (Ac-CoA) is a core metabolite with essential roles throughout cell physiology. These functions can be classified into energetics, biosynthesis, regulation and acetylation of large and small molecules. Ac-CoA is essential for oxidative metabolism of glucose, fatty acids, most amino acids, ethanol, and of free acetate generated by endogenous metabolism or by gut bacteria. Ac-CoA cannot cross lipid bilayers, but acetyl groups from Ac-CoA can shuttle across membranes as part of carrier molecules like citrate or acetylcarnitine, or as free acetate or ketone bodies. Ac-CoA is the basic unit of lipid biosynthesis, providing essentially all of the carbon for the synthesis of fatty acids and of isoprenoid-derived compounds including cholesterol, coenzyme Q and dolichols. High levels of Ac-CoA in hepatocytes stimulate lipid biosynthesis, ketone body production and the diversion of pyruvate metabolism towards gluconeogenesis and away from oxidation; low levels exert opposite effects. Acetylation changes the properties of molecules. Acetylation is necessary for the synthesis of acetylcholine, acetylglutamate, acetylaspartate and N-acetyl amino sugars, and to metabolize/eliminate some xenobiotics. Acetylation is a major post-translational modification of proteins. Different types of protein acetylation occur. The most-studied form occurs at the epsilon nitrogen of lysine residues. In histones, lysine acetylation can alter gene transcription. Acetylation of other proteins has diverse, often incompletely-documented effects. Inborn errors related to Ac-CoA feature a broad spectrum of metabolic, neurological and other features. To date, a small number of studies of animals with inborn errors of CoA thioesters has included direct measurement of acyl-CoAs. These studies have shown that low levels of tissue Ac-CoA correlate with the development of clinical signs, hinting that shortage of Ac-CoA may be a recurrent theme in these conditions. Low levels of Ac-CoA could potentially disrupt any of its roles.

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.

Role of the MOZ/MLL-mediated transcriptional activation system for self-renewal in normal hematopoiesis and leukemogenesis

Homeostasis in the blood system is maintained by the balance between self-renewing stem cells and nonstem cells. To promote self-renewal, transcriptional regulators maintain epigenetic information during multiple rounds of cell division. Mutations in such transcriptional regulators cause aberrant self-renewal, leading to leukemia. MOZ, a histone acetyltransferase, and MLL, a histone methyltransferase, are transcriptional regulators that promote the self-renewal of hematopoietic stem cells. Gene rearrangements of MOZ and MLL generate chimeric genes encoding fusion proteins that function as constitutively active forms. These MOZ and MLL fusion proteins constitutively activate transcription of their target genes and cause aberrant self-renewal in committed hematopoietic progenitors, which normally do not self-renew. Recent progress in the field suggests that MOZ and MLL are part of a transcriptional activation system that activates the transcription of genes with nonmethylated CpG-rich promoters. The nonmethylated state of CpGs is normally maintained during cell divisions from the mother cell to the daughter cells. Thus, the MOZ/MLL-mediated transcriptional activation system replicates the expression profile of mother cells in daughter cells by activating the transcription of genes previously transcribed in the mother cell. This review summarizes the functions of the components of the MOZ/MLL-mediated transcriptional activation system and their roles in the promotion of self-renewal.

BRPF1-KAT6A/KAT6B Complex: Molecular Structure, Biological Function and Human Disease

The bromodomain and PHD finger–containing protein1 (BRPF1) is a member of family IV of the bromodomain-containing proteins that participate in the post-translational modification of histones. It functions in the form of a tetrameric complex with a monocytic leukemia zinc finger protein (MOZ or KAT6A), MOZ-related factor (MORF or KAT6B) or HAT bound to ORC1 (HBO1 or KAT7) and two small non-catalytic proteins, the inhibitor of growth 5 (ING5) or the paralog ING4 and MYST/Esa1-associated factor 6 (MEAF6). Mounting studies have demonstrated that all the four core subunits play crucial roles in different biological processes across diverse species, such as embryonic development, forebrain development, skeletal patterning and hematopoiesis. BRPF1, KAT6A and KAT6B mutations were identified as the cause of neurodevelopmental disorders, leukemia, medulloblastoma and other types of cancer, with germline mutations associated with neurodevelopmental disorders displaying intellectual disability, and somatic variants associated with leukemia, medulloblastoma and other cancers. In this paper, we depict the molecular structures and biological functions of the BRPF1-KAT6A/KAT6B complex, summarize the variants of the complex related to neurodevelopmental disorders and cancers and discuss future research directions and therapeutic potentials.

Molecular Insights into the Recognition of Acetylated Histone Modifications by the BRPF2 Bromodomain

HBO1 [HAT bound to the origin recognition complex (ORC)], a member of the MYST family of histone acetyltransferases (HATs), was initially identified as a binding partner of ORC that acetylates free histone H3, H4, and nucleosomal H3. It functions as a quaternary complex with the BRPF (BRPF1/2/3) scaffolding protein and two accessory proteins, ING4/5 and Eaf6. Interaction of BRPF2 with HBO1 has been shown to be important for regulating H3K14 acetylation during embryonic development. However, how BRPF2 directs the HBO1 HAT complex to chromatin to regulate its HAT activity toward nucleosomal substrates remains unclear. Our findings reveal novel interacting partners of the BRPF2 bromodomain that recognizes different acetyllysine residues on the N-terminus of histone H4, H3, and H2A and preferentially binds to H4K5ac, H4K8ac, and H4K5acK12ac modifications. In addition, mutational analysis of the BRPF2 bromodomain coupled with isothermal titration calorimetry binding and pull-down assays on the histone substrates identified critical residues responsible for acetyllysine binding. Moreover, the BRPF2 bromodomain could enrich H4K5ac mark-bearing mononucleosomes compared to other acetylated H4 marks. Consistent with this, ChIP-seq analysis revealed that BRPF2 strongly co-localizes with HBO1 at histone H4K5ac and H4K8ac marks near the transcription start sites in the genome. Our study provides novel insights into how the histone binding function of the BRPF2 bromodomain directs the recruitment of the HBO1 HAT complex to chromatin to regulate gene expression.

Loss of TIP60 (KAT5) abolishes H2AZ lysine 7 acetylation and causes p53, INK4A, and ARF-independent cell cycle arrest

Histone acetylation is essential for initiating and maintaining a permissive chromatin conformation and gene transcription. Dysregulation of histone acetylation can contribute to tumorigenesis and metastasis. Using inducible cre-recombinase and CRISPR/Cas9-mediated deletion, we investigated the roles of the histone lysine acetyltransferase TIP60 (KAT5/HTATIP) in human cells, mouse cells, and mouse embryos. We found that loss of TIP60 caused complete cell growth arrest. In the absence of TIP60, chromosomes failed to align in a metaphase plate during mitosis. In some TIP60 deleted cells, endoreplication occurred instead. In contrast, cell survival was not affected. Remarkably, the cell growth arrest caused by loss of TIP60 was independent of the tumor suppressors p53, INK4A and ARF. TIP60 was found to be essential for the acetylation of H2AZ, specifically at lysine 7. The mRNA levels of 6236 human and 8238 mouse genes, including many metabolism genes, were dependent on TIP60. Among the top 50 differentially expressed genes, over 90% were downregulated in cells lacking TIP60, supporting a role for TIP60 as a key co-activator of transcription. We propose a primary role of TIP60 in H2AZ lysine 7 acetylation and transcriptional activation, and that this fundamental role is essential for cell proliferation. Growth arrest independent of major tumor suppressors suggests TIP60 as a potential anti-cancer drug target.

A synthetic lethality screen reveals ING5 as a genetic dependency of catalytically dead Set1A/COMPASS in mouse embryonic stem cells

Embryonic stem cells (ESCs) are defined by their ability to self-renew and the potential to differentiate into all tissues of the developing organism. We previously demonstrated that deleting the catalytic SET domain of the Set1A/complex of proteins associated with SET1 histone methyltransferase (Set1A/COMPASS) in mouse ESCs does not impair their viability or ability to self-renew; however, it leads to defects in differentiation. The precise mechanisms by which Set1A executes these functions remain to be elucidated. In this study, we demonstrate that mice lacking the SET domain of Set1A are embryonic lethal at a stage that is unique from null alleles. To gain insight into Set1A function in regulating pluripotency, we conducted a CRISPR/Cas9-mediated dropout screen and identified the MOZ/MORF (monocytic leukaemia zinc finger protein/monocytic leukaemia zinc finger protein-related factor) and HBO1 (HAT bound to ORC1) acetyltransferase complex member ING5 as a synthetic perturbation to Set1A. The loss of Ing5 in Set1AΔSET mouse ESCs decreases the fitness of these cells, and the simultaneous loss of ING5 and in Set1AΔSET leads to up-regulation of differentiation-associated genes. Taken together, our results point toward Set1A/COMPASS and ING5 as potential coregulators of the self-renewal and differentiation status of ESCs.

Retusone A, a Guaiane-Type Sesquiterpene Dimer from Wikstroemia retusa and Its Inhibitory Effects on Histone Acetyltransferase HBO1 Expression

Retusone A (1), a new sesquiterpene dimer consisting of two guaiane-type sesquiterpenoids, and oleodaphnal (2) were isolated from heartwood of Wikstroemia retusa (Thymelaeaceae). The planar structure of 1 was elucidated on the basis of HRESIMS and NMR spectroscopic data, and the relative stereochemistry was established by X-ray diffraction analysis. The absolute configuration of 1 was determined by electronic circular dichroism. Compound 1 suppressed luciferase reporter gene expression driven by the HBO1 (histone acetyltransferase binding to ORC1) gene promoter in human breast cancer MCF7 cells. Compound 1 also decreased the expression of endogenous HBO1 mRNA and protein, and inhibited proliferation of the cells. These results suggest that retusone A (1), which has a unique dimeric sesquiterpenoid structure with inhibitory activity against HBO1 expression, may contribute to the development of a novel therapeutic candidate for the treatment of breast cancer.

NOGOB receptor deficiency increases cerebrovascular permeability and hemorrhage via impairing histone acetylation-mediated CCM1/2 expression

The loss function of cerebral cavernous malformation (CCM) genes leads to most CCM lesions characterized by enlarged leaking vascular lesions in the brain. Although we previously showed that NOGOB receptor (NGBR) knockout in endothelial cells (ECs) results in cerebrovascular lesions in the mouse embryo, the molecular mechanism by which NGBR regulates CCM1/2 expression has not been elucidated. Here, we show that genetic depletion of Ngbr in ECs at both postnatal and adult stages results in CCM1/2 expression deficiency and cerebrovascular lesions such as enlarged vessels, blood-brain-barrier hyperpermeability, and cerebral hemorrhage. To reveal the molecular mechanism, we used RNA-sequencing analysis to examine changes in the transcriptome. Surprisingly, we found that the acetyltransferase HBO1 and histone acetylation were downregulated in NGBR-deficient ECs. The mechanistic studies elucidated that NGBR is required for maintaining the expression of CCM1/2 in ECs via HBO1-mediated histone acetylation. ChIP-qPCR data further demonstrated that loss of NGBR impairs the binding of HBO1 and acetylated histone H4K5 and H4K12 on the promotor of the CCM1 and CCM2 genes. Our findings on epigenetic regulation of CCM1 and CCM2 that is modulated by NGBR and HBO1-mediated histone H4 acetylation provide a perspective on the pathogenesis of sporadic CCMs.

The histone lysine acetyltransferase HBO1 (KAT7) regulates hematopoietic stem cell quiescence and self-renewal

The histone acetyltransferase HBO1 (MYST2, KAT7) is indispensable for postgastrulation development, histone H3 lysine 14 acetylation (H3K14Ac), and the expression of embryonic patterning genes. In this study, we report the role of HBO1 in regulating hematopoietic stem cell function in adult hematopoiesis. We used 2 complementary cre-recombinase transgenes to conditionally delete Hbo1 (Mx1-Cre and Rosa26-CreERT2). Hbo1-null mice became moribund due to hematopoietic failure with pancytopenia in the blood and bone marrow 2 to 6 weeks after Hbo1 deletion. Hbo1-deleted bone marrow cells failed to repopulate hemoablated recipients in competitive transplantation experiments. Hbo1 deletion caused a rapid loss of hematopoietic progenitors. The numbers of lineage-restricted progenitors for the erythroid, myeloid, B-, and T-cell lineages were reduced. Loss of HBO1 resulted in an abnormally high rate of recruitment of quiescent hematopoietic stem cells (HSCs) into the cell cycle. Cycling HSCs produced progenitors at the expense of self-renewal, which led to the exhaustion of the HSC pool. Mechanistically, genes important for HSC functions were downregulated in HSC-enriched cell populations after Hbo1 deletion, including genes essential for HSC quiescence and self-renewal, such as Mpl, Tek(Tie-2), Gfi1b, Egr1, Tal1(Scl), Gata2, Erg, Pbx1, Meis1, and Hox9, as well as genes important for multipotent progenitor cells and lineage-specific progenitor cells, such as Gata1. HBO1 was required for H3K14Ac through the genome and particularly at gene loci required for HSC quiescence and self-renewal. Our data indicate that HBO1 promotes the expression of a transcription factor network essential for HSC maintenance and self-renewal in adult hematopoiesis.

Lysine Acetyltransferases and Their Role in AR Signaling and Prostate Cancer

The development and growth of a normal prostate gland, as well as its physiological functions, are regulated by the actions of androgens through androgen receptor (AR) signaling which drives multiple cellular processes including transcription, cellular proliferation, and apoptosis in prostate cells. Post-translational regulation of AR plays a vital role in directing its cellular activities via modulating its stability, nuclear localization, and transcriptional activity. Among various post-translational modifications (PTMs), acetylation is an essential PTM recognized in AR and is governed by the regulated actions of acetyltransferases and deacetyltransferases. Acetylation of AR has been identified as a critical step for its activation and depending on the site of acetylation, the intracellular dynamics and activity of the AR can be modulated. Various acetyltransferases such as CBP, p300, PCAF, TIP60, and ARD1 that are known to acetylate AR, may directly coactivate the AR transcriptional function or help to recruit additional coactivators to functionally regulate the transcriptional activity of the AR. Aberrant expression of acetyltransferases and their deregulated activities have been found to interfere with AR signaling and play a key role in development and progression of prostatic diseases, including prostate cancer (PCa). In this review, we summarized recent research advances aimed at understanding the role of various lysine acetyltransferases (KATs) in the regulation of AR activity at the level of post-translational modifications in normal prostate physiology, as well as in development and progression of PCa. Considering the critical importance of KATs in modulating AR activity in physiological and patho-physiological context, we further discussed the potential of targeting these enzymes as a therapeutic option to treat AR-related pathology in combination with hormonal therapy.

Histone acetyltransferases MystA and MystB contribute to morphogenesis and aflatoxin biosynthesis by regulating acetylation in fungus Aspergillus flavus

Myst family is highly conserved histone acetyltransferases in eukaryotic cells and is known to play crucial roles in various cellular processes; however, acetylation catalysed by acetyltransferases is unclear in filamentous fungi. Here, we identified two classical nonessential Myst enzymes and analysed their functions in Aspergillus flavus, which generates aflatoxin B1, one of the most carcinogenic secondary metabolites. MystA and MystB located in nuclei and cytoplasm, and mystA could acetylate H4K16ac, while mystB acetylates H3K14ac, H3K18ac and H3K23ac. Deletion mystA resulted in decreased conidiation, increased sclerotia formation and aflatoxin production. Deletion of mystB leads to significant defects in conidiation, sclerotia formation and aflatoxin production. Additionally, double-knockout mutant (ΔmystA/mystB) display a stronger and similar defect to ΔmystB mutant, indicating that mystB plays a major role in regulating development and aflatoxin production. Both mystA and mystB play important role in crop colonization. Moreover, catalytic domain MOZ and the catalytic site E199/E243 were important for the acetyltransferase function of Myst. Notably, chromatin immunoprecipitation results indicated that mystB participated in oxidative detoxification by regulating the acetylation level of H3K14, and further regulated nsdD to affect sclerotia formation and aflatoxin production. This study provides new evidences to discover the biological functions of histone acetyltransferase in A. flavus.

Insights into the Molecular Mechanisms of Histone Code Recognition by the BRPF3 Bromodomain

Bromodomains are evolutionarily conserved reader modules that recognize acetylated lysine residues on the histone tails to facilitate gene transcription. The bromodomain and PHD finger containing protein 3 (BRPF3) is a scaffolding protein that forms a tetrameric complex with HBO1 histone acetyltransferase (HAT) and two other subunits, which is known to regulate the HAT activity and substrate specificity. However, its molecular mechanism, histone ligands, and biological functions remain unknown. Herein, we identify mono- (H4K5ac) and di- (H4K5acK12ac) acetylated histone peptides as novel interacting partners of the BRPF3 bromodomain. Consistent with this, pull-down assays on purified histones from human cells confirm the interaction of BRPF3 bromodomain with acetylated histone H4. Further, MD simulation studies highlight the binding mode of acetyllysine (Kac) and the stability of bromodomain-histone peptide complexes. Collectively, our findings provide a key insight into how histone targets of the BRPF3 bromodomain direct the recruitment of HBO1 complex to chromatin for downstream transcriptional regulation.

The histone acetyltransferase HBO1 promotes efficient tip cell sprouting during angiogenesis

Blood vessel growth and remodelling are essential during embryonic development and disease pathogenesis. The diversity of endothelial cells (ECs) is transcriptionally evident and ECs undergo dynamic changes in gene expression during vessel growth and remodelling. Here, we investigated the role of the histone acetyltransferase HBO1 (KAT7), which is important for activating genes during development and for histone H3 lysine 14 acetylation (H3K14ac). Loss of HBO1 and H3K14ac impaired developmental sprouting angiogenesis and reduced pathological EC overgrowth in the retinal endothelium. Single-cell RNA sequencing of retinal ECs revealed an increased abundance of tip cells in Hbo1-deficient retinas, which led to EC overcrowding in the retinal sprouting front and prevented efficient tip cell migration. We found that H3K14ac was highly abundant in the endothelial genome in both intra- and intergenic regions, suggesting that HBO1 acts as a genome organiser that promotes efficient tip cell behaviour necessary for sprouting angiogenesis. This article has an associated 'The people behind the papers' interview.

HBO1 is a versatile histone acyltransferase critical for promoter histone acylations

Recent studies demonstrate that histones are subjected to a series of short-chain fatty acid modifications that is known as histone acylations. However, the enzymes responsible for histone acylations in vivo are not well characterized. Here, we report that HBO1 is a versatile histone acyltransferase that catalyzes not only histone acetylation but also propionylation, butyrylation and crotonylation both in vivo and in vitro and does so in a JADE or BRPF family scaffold protein-dependent manner. We show that the minimal HBO1/BRPF2 complex can accommodate acetyl-CoA, propionyl-CoA, butyryl-CoA and crotonyl-CoA. Comparison of CBP and HBO1 reveals that they catalyze histone acylations at overlapping as well as distinct sites, with HBO1 being the key enzyme for H3K14 acylations. Genome-wide chromatin immunoprecipitation assay demonstrates that HBO1 is highly enriched at and contributes to bulk histone acylations on the transcriptional start sites of active transcribed genes. HBO1 promoter intensity highly correlates with the level of promoter histone acylation, but has no significant correlation with level of transcription. We also show that HBO1 is associated with a subset of DNA replication origins. Collectively our study establishes HBO1 as a versatile histone acyltransferase that links histone acylations to promoter acylations and selection of DNA replication origins.

A genome-wide CRISPR-based screen identifies KAT7 as a driver of cellular senescence

Understanding the genetic and epigenetic bases of cellular senescence is instrumental in developing interventions to slow aging. We performed genome-wide CRISPR-Cas9-based screens using two types of human mesenchymal precursor cells (hMPCs) exhibiting accelerated senescence. The hMPCs were derived from human embryonic stem cells carrying the pathogenic mutations that cause the accelerated aging diseases Werner syndrome and Hutchinson-Gilford progeria syndrome. Genes whose deficiency alleviated cellular senescence were identified, including KAT7, a histone acetyltransferase, which ranked as a top hit in both progeroid hMPC models. Inactivation of KAT7 decreased histone H3 lysine 14 acetylation, repressed p15^INK4b transcription, and alleviated hMPC senescence. Moreover, lentiviral vectors encoding Cas9/sg-Kat7, given intravenously, alleviated hepatocyte senescence and liver aging and extended life span in physiologically aged mice as well as progeroid Zmpste24^-/- mice that exhibit a premature aging phenotype. CRISPR-Cas9-based genetic screening is a robust method for systematically uncovering senescence genes such as KAT7, which may represent a therapeutic target for developing aging interventions.

KAT7 is a genetic vulnerability of acute myeloid leukemias driven by MLL rearrangements

Histone acetyltransferases (HATs) catalyze the transfer of an acetyl group from acetyl-CoA to lysine residues of histones and play a central role in transcriptional regulation in diverse biological processes. Dysregulation of HAT activity can lead to human diseases including developmental disorders and cancer. Through genome-wide CRISPR-Cas9 screens, we identified several HATs of the MYST family as fitness genes for acute myeloid leukemia (AML). Here we investigate the essentiality of lysine acetyltransferase KAT7 in AMLs driven by the MLL-X gene fusions. We found that KAT7 loss leads to a rapid and complete loss of both H3K14ac and H4K12ac marks, in association with reduced proliferation, increased apoptosis, and differentiation of AML cells. Acetyltransferase activity of KAT7 is essential for the proliferation of these cells. Mechanistically, our data propose that acetylated histones provide a platform for the recruitment of MLL-fusion-associated adaptor proteins such as BRD4 and AF4 to gene promoters. Upon KAT7 loss, these factors together with RNA polymerase II rapidly dissociate from several MLL-fusion target genes that are essential for AML cell proliferation, including MEIS1, PBX3, and SENP6. Our findings reveal that KAT7 is a plausible therapeutic target for this poor prognosis AML subtype.

A unique histone 3 lysine 14 chromatin signature underlies tissue-specific gene regulation

Organismal development and cell differentiation critically depend on chromatin state transitions. However, certain developmentally regulated genes lack histone 3 lysine 9 and 27 acetylation (H3K9ac and H3K27ac, respectively) and histone 3 lysine 4 (H3K4) methylation, histone modifications common to most active genes. Here we describe a chromatin state featuring unique histone 3 lysine 14 acetylation (H3K14ac) peaks in key tissue-specific genes in Drosophila and human cells. Replacing H3K14 in Drosophila demonstrates that H3K14 is essential for expression of genes devoid of canonical histone modifications in the embryonic gut and larval wing imaginal disc, causing lethality and defective wing patterning. We find that the SWI/SNF protein Brahma (Brm) recognizes H3K14ac, that brm acts in the same genetic pathway as H3K14R, and that chromatin accessibility at H3K14ac-unique genes is decreased in H3K14R mutants. Our results show that acetylation of a single lysine is essential at genes devoid of canonical histone marks and uncover an important requirement for H3K14 in tissue-specific gene regulation.

NCAPG2 facilitates glioblastoma cells' malignancy and xenograft tumor growth via HBO1 activation by phosphorylation

NCAPG2 (non-SMC condensin II complex subunit G2), as an important factor in cell mitosis, has been the focus in the study of different cancers. However, the role of NCAPG2 in the malignancy of glioblastoma cells remains unknown. The findings from the present study demonstrated that NCAPG2 was significantly increased in human glioblastoma tissues and was associated with poor clinical outcome. Moreover, NCAPG2 could promote proliferation, migration, and invasion and regulate cell cycle in glioblastoma cells. Investigation of the molecular mechanism indicated that NCAPG2 regulated HBO1 phosphorylation and H4 histone acetylase activation, modulated the activation of Wnt/β-catenin pathway, and the binding of MCM protein to chromatin to exert its role. Furthermore, knockdown of HBO1 was found to reverse the effect of NCAPG2 overexpression on cell proliferation, migration, invasion, and cell cycle. In addition, knockdown of NCAPG2 attenuated glioblastoma tumorigenesis in vivo. Taken together, the findings demonstrated that NCAPG2 facilitates the malignancy of glioblastoma cells and xenograft tumor growth via HBO1 activation by phosphorylation. These results improve our understanding of the mechanism underlying glioblastoma progression and may contribute to the identification of novel biomarkers and therapeutic targets for glioblastoma.

Lysine acetyltransferase 8 is involved in cerebral development and syndromic intellectual disability

Epigenetic integrity is critical for many eukaryotic cellular processes. An important question is how different epigenetic regulators control development and influence disease. Lysine acetyltransferase 8 (KAT8) is critical for acetylation of histone H4 at lysine 16 (H4K16), an evolutionarily conserved epigenetic mark. It is unclear what roles KAT8 plays in cerebral development and human disease. Here, we report that cerebrum-specific knockout mice displayed cerebral hypoplasia in the neocortex and hippocampus, along with improper neural stem and progenitor cell (NSPC) development. Mutant cerebrocortical neuroepithelia exhibited faulty proliferation, aberrant neurogenesis, massive apoptosis, and scant H4K16 propionylation. Mutant NSPCs formed poor neurospheres, and pharmacological KAT8 inhibition abolished neurosphere formation. Moreover, we describe KAT8 variants in 9 patients with intellectual disability, seizures, autism, dysmorphisms, and other anomalies. The variants altered chromobarrel and catalytic domains of KAT8, thereby impairing nucleosomal H4K16 acetylation. Valproate was effective for treating epilepsy in at least 2 of the individuals. This study uncovers a critical role of KAT8 in cerebral and NSPC development, identifies 9 individuals with KAT8 variants, and links deficient H4K16 acylation directly to intellectual disability, epilepsy, and other developmental anomalies.

The DPF Domain As a Unique Structural Unit Participating in Transcriptional Activation, Cell Differentiation, and Malignant Transformation

The DPF (double PHD finger) domain consists of two PHD fingers organized in tandem. The two PHD-finger domains within a DPF form a single structure that interacts with the modification of the N-terminal histone fragment in a way different from that for single PHD fingers. Several histone modifications interacting with the DPF domain have already been identified. They include acetylation of H3K14 and H3K9, as well as crotonylation of H3K14. These modifications are found predominantly in transcriptionally active chromatin. Proteins containing DPF belong to two classes of protein complexes, which are the transcriptional coactivators involved in the regulation of the chromatin structure. These are the histone acetyltransferase complex belonging to the MYST family and the SWI/SNF chromatin-remodeling complex. The DPF domain is responsible for the specificity of the interactions between these complexes and chromatin. Proteins containing DPF play a crucial role in the activation of the transcription of a number of genes expressed during the development of an organism. These genes are important in the differentiation and malignant transformation of mammalian cells.

lnc-BAZ2B promotes M2 macrophage activation and inflammation in children with asthma through stabilizing BAZ2B pre-mRNA

BACKGROUND

Dysregulation of long noncoding RNAs (lncRNAs) is associated with a variety of human diseases; however, whether they have a role in childhood asthma is unknown.

OBJECTIVE

We sought to determine the differential expression profiles of lncRNAs in PBMCs of children with asthma and the mechanisms underlying the effects of lncRNAs on the pathogenesis of asthma.

METHODS

The differential expression profiles of lncRNAs were analyzed by transcriptome microarray. The effects and mechanisms by which lncRNAs influence macrophage activation were detected by real-time quantitative PCR, Western blot, RNase protection assay, and chromatin immunoprecipitation assay. The roles played by lncRNAs in asthma were tested in a cockroach allergen extract (CRE)-induced mouse model.

RESULTS

We identified 719 lncRNAs that were differentially expressed in PBMCs of children with asthma, 502 of which were upregulated and 217 were downregulated. An lncRNA of unknown function, lnc-BAZ2B, was dominantly expressed in monocytes and significantly upregulated in children with asthma. lnc-BAZ2B promotes M2 macrophage activation by enhancing BAZ2B expression and exacerbated lung inflammation in an M2 macrophage-associated CRE-induced asthma model. Mechanistically, lnc-BAZ2B promoted the expression of its cis target gene BAZ2B by stabilizing its pre-mRNA. BAZ2B, a reader of H3K14ac modification, enhanced the transcription of IRF4 and promoted M2 macrophage activation. lnc-BAZ2B expression was correlated with that of BAZ2B in PBMCs from children with asthma. Baz2b knockdown could alleviate asthma severity in a CRE-induced asthma model.

CONCLUSION

lnc-BAZ2B promotes M2 macrophage activation and inflammation in children with asthma and may serve as a potential therapeutic and diagnostic target in children with asthma.

Reduced Brd1 expression leads to reversible depression-like behaviors and gene-expression changes in female mice

The schizophrenia-associated gene, BRD1, encodes an epigenetic regulator in which chromatin interactome is enriched with genes implicated in mental health. Alterations in histone modifications and epigenetic regulation contribute to brain transcriptomic changes in affective disorders and preclinical data supports a role for BRD1 in psychopathology. However, the implication of BRD1 on affective pathology remains poorly understood. In this study, we assess affective behaviors and associated neurobiology in Brd1^+/- mice along with their responses to Fluoxetine and Imipramine. This involves behavioral, neurostructural, and neurochemical characterizations along with regional cerebral gene expression profiling combined with integrative functional genomic analyses. We report behavioral changes in female Brd1^+/- mice with translational value to depressive symptomatology that can be alleviated by the administration of antidepressant medications. Behavioral changes are accompanied by altered brain morphometry and imbalances in monoaminergic systems. In accordance, gene expression changes across brain tissues reveal altered neurotransmitter signaling and cluster in functional pathways associated with depression including 'Adrenergic-, GPCR-, cAMP-, and CREB/CREM-signaling'. Integrative gene expression analysis specifically links changes in amygdaloid intracellular signaling activity to the behavioral treatment response in Brd1^+/- mice. Collectively, our study highlights the importance of BRD1 as a modulator of affective pathology and adds to our understanding of the molecular mechanisms underlying affective disorders and their treatment response.

Deciphering structure, function and mechanism of lysine acetyltransferase HBO1 in protein acetylation, transcription regulation, DNA replication and its oncogenic properties in cancer

HBO1 complexes are major acetyltransferase responsible for histone H4 acetylation in vivo, which belongs to the MYST family. As the core catalytic subunit, HBO1 consists of an N-terminal domain and a C-terminal MYST domain that are in charge of acetyl-CoA binding and acetylation reaction. HBO1 complexes are multimeric and normally consist of two native subunits MEAF6, ING4 or ING5 and two kinds of cofactors as chromatin reader: Jade-1/2/3 and BRPF1/2/3. The choices of subunits to form the HBO1 complexes provide a regulatory switch to potentiate its activity between histone H4 and H3 tails. Thus, HBO1 complexes present multiple functions in histone acetylation, gene transcription, DNA replication, protein ubiquitination, and immune regulation, etc. HBO1 is a co-activator for CDT1 to facilitate chromatin loading of MCM complexes and promotes DNA replication licensing. This process is regulated by mitotic kinases such as CDK1 and PLK1 by phosphorylating HBO1 and modulating its acetyltransferase activity, therefore, connecting histone acetylation to regulations of cell cycle and DNA replication. In addition, both gene amplification and protein overexpression of HBO1 confirmed its oncogenic role in cancers. In this paper, we review the recent advances and discuss our understanding of the multiple functions, activity regulation, and disease relationship of HBO1.

HBO1 (KAT7) Does Not Have an Essential Role in Cell Proliferation, DNA Replication, or Histone 4 Acetylation in Human Cells

HBO1 (MYST2/KAT7) is essential for histone 3 lysine 14 acetylation (H3K14ac) but is dispensable for H4 acetylation and DNA replication in mouse tissues. In contrast, previous studies using small interfering RNA (siRNA) knockdown in human cell lines have suggested that HBO1 is essential for DNA replication. To determine if HBO1 has distinctly different roles in immortalized human cell lines and normal mouse cells, we performed siRNA knockdown of HBO1. In addition, we used CRISPR/Cas9 to generate 293T, MCF7, and HeLa cell lines lacking HBO1. Using both techniques, we show that HBO1 is essential for all H3K14ac in human cells and is unlikely to have a direct effect on H4 acetylation and only has minor effects on cell proliferation. Surprisingly, the loss of HBO1 and H3K14ac in HeLa cells led to the secondary loss of almost all H4 acetylation after 4 weeks. Thus, HBO1 is dispensable for DNA replication and cell proliferation in immortalized human cells. However, while cell proliferation proceeded without HBO1 and H3K14ac, HBO1 gene deletion led to profound changes in cell adhesion, particularly in 293T cells. Consistent with this phenotype, the loss of HBO1 in both 293T and HeLa principally affected genes mediating cell adhesion, with comparatively minor effects on other cellular processes.

The Protective Effect of HBO1 on Cigarette Smoke Extract-Induced Apoptosis in Airway Epithelial Cells

Purpose

Epigenetic modification is one of most important mechanisms underlying the pathogenesis of chronic obstructive pulmonary disease (COPD). The purpose of this study was to determine whether histone acetyltransferase binding to ORC1 (HBO1) can protect against cigarette smoke (CS)-induced cell apoptosis and sustain normal histone acetylation in COPD.

Methods

Human lung tissue samples were obtained from patients who underwent lung resection. The emphysema mouse model and HBO1 overexpressing mice were each established by intraperitoneal injection with cigarette smoke extract (CSE) or intratracheal lentiviral vectors instillation. TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assays were used to assess apoptotic ratio in mice. The apoptosis of human bronchial epithelial cells (HBECs) was assayed by flow cytometry. HBO1, B-cell lymphoma-2 (BCL-2), and H3K14ac protein expression were detected by Western blotting. HBO1 mRNA expression was measured by quantitative real-time polymerase chain reaction.

Results

Protein expression of HBO1 was decreased significantly in lung tissue from COPD patients and CSE-treated emphysema mouse models. Overexpression of HBO1 attenuated CSE-induced emphysematous changes, as well as apoptosis in the lungs of COPD mice. In vitro, the HBO1 protein degraded in a time- and dose-dependent course with CSE treatment. With flow cytometry, we proved that HBO1 could reverse the apoptosis of HBECs induced by CSE. Furthermore, HBO1 overexpression promoted the expression of anti-apoptotic BCL-2 protein and enhanced H3K14 acetylation in airway epithelial cells.

Conclusion

These findings demonstrate that the key histone modulator HBO1 plays a protective role in COPD pathogenesis that may shed light on potential therapeutic targets to inhibit the progress of COPD.

Deficient histone H3 propionylation by BRPF1-KAT6 complexes in neurodevelopmental disorders and cancer

Lysine acetyltransferase 6A (KAT6A) and its paralog KAT6B form stoichiometric complexes with bromodomain- and PHD finger-containing protein 1 (BRPF1) for acetylation of histone H3 at lysine 23 (H3K23). We report that these complexes also catalyze H3K23 propionylation in vitro and in vivo. Immunofluorescence microscopy and ATAC-See revealed the association of this modification with active chromatin. Brpf1 deletion obliterates the acylation in mouse embryos and fibroblasts. Moreover, we identify BRPF1 variants in 12 previously unidentified cases of syndromic intellectual disability and demonstrate that these cases and known BRPF1 variants impair H3K23 propionylation. Cardiac anomalies are present in a subset of the cases. H3K23 acylation is also impaired by cancer-derived somatic BRPF1 mutations. Valproate, vorinostat, propionate and butyrate promote H3K23 acylation. These results reveal the dual functionality of BRPF1-KAT6 complexes, shed light on mechanisms underlying related developmental disorders and various cancers, and suggest mutation-based therapy for medical conditions with deficient histone acylation.

HBO1 is required for the maintenance of leukaemia stem cells

Acute myeloid leukaemia (AML) is a heterogeneous disease characterized by transcriptional dysregulation that results in a block in differentiation and increased malignant self-renewal. Various epigenetic therapies aimed at reversing these hallmarks of AML have progressed into clinical trials, but most show only modest efficacy owing to an inability to effectively eradicate leukaemia stem cells (LSCs)1. Here, to specifically identify novel dependencies in LSCs, we screened a bespoke library of small hairpin RNAs that target chromatin regulators in a unique ex vivo mouse model of LSCs. We identify the MYST acetyltransferase HBO1 (also known as KAT7 or MYST2) and several known members of the HBO1 protein complex as critical regulators of LSC maintenance. Using CRISPR domain screening and quantitative mass spectrometry, we identified the histone acetyltransferase domain of HBO1 as being essential in the acetylation of histone H3 at K14. H3 acetylated at K14 (H3K14ac) facilitates the processivity of RNA polymerase II to maintain the high expression of key genes (including Hoxa9 and Hoxa10) that help to sustain the functional properties of LSCs. To leverage this dependency therapeutically, we developed a highly potent small-molecule inhibitor of HBO1 and demonstrate its mode of activity as a competitive analogue of acetyl-CoA. Inhibition of HBO1 phenocopied our genetic data and showed efficacy in a broad range of human cell lines and primary AML cells from patients. These biological, structural and chemical insights into a therapeutic target in AML will enable the clinical translation of these findings.