Monocytic leukemia zinc finger protein is essential for the development of long-term reconstituting hematopoietic stem cells

The small inhibitor WM-1119 effectively targets KAT6A-rearranged AML, but not KMT2A-rearranged AML, despite shared KAT6 genetic dependency

BACKGROUND

The epigenetic factors KAT6A (MOZ/MYST3) and KMT2A (MLL/MLL1) interact in normal hematopoiesis to regulate progenitors' self-renewal. Both proteins are recurrently translocated in AML, leading to impairment of critical differentiation pathways in these malignant cells. We evaluated the potential of different KAT6A therapeutic targeting strategies to alter the growth of KAT6A and KMT2A rearranged AMLs.

METHODS

We investigated the action and potential mechanisms of the first-in-class KAT6A inhibitor, WM-1119 in KAT6A and KMT2A rearranged (KAT6Ar and KMT2Ar) AML using cellular (flow cytometry, colony assays, cell growth) and molecular (shRNA knock-down, CRISPR knock-out, bulk and single-cell RNA-seq, ChIP-seq) assays. We also used two novel genetic murine KAT6A models combined with the most common KMT2Ar AML, KMT2A::MLLT3 AML. In these murine models, the catalytic activity of KAT6A, or the whole protein, can be conditionally abrogated or deleted. These models allowed us to compare the effects of specific KAT6A KAT activity inhibition with the complete deletion of the whole protein. Finally, we also tested these therapeutic approaches on human AML cell lines and primary patient AMLs.

RESULTS

We found that WM-1119 completely abrogated the proliferative and clonogenic potential of KAT6Ar cells in vitro. WM-1119 treatment was associated with a dramatic increase in myeloid differentiation program. The treatment also decreased stemness and leukemia pathways at the transcriptome level and led to loss of binding of the fusion protein at critical regulators of these pathways. In contrast, our pharmacologic and genetic results indicate that the catalytic activity of KAT6A plays a more limited role in KMT2Ar leukemogenicity, while targeting the whole KAT6A protein dramatically affects leukemic potential in murine KMT2A::MLLT3 AML.

CONCLUSION

Our study indicates that inhibiting KAT6A KAT activity holds compelling promise for KAT6Ar AML patients. In contrast, targeted degradation of KAT6A, and not just its catalytic activity, may represent a more appropriate therapeutic approach for KMT2Ar AMLs.

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.

EPC1/2 regulate hematopoietic stem and progenitor cell proliferation by modulating H3 acetylation and DLST

Enhancers of polycomb 1 (EPC1) and 2 (EPC2) are involved in multiple biological processes as components of histone acetyltransferases/deacetylase complexes and transcriptional cofactors, and their dysfunction was associated with developmental defects and diseases. However, it remains unknown how their dysfunction induces hematopoietic stem and progenitor cell (HSPC) defects. Here, we show that depletion of EPC1/2 significantly reduced the number of hematopoietic stem and progenitor cells (HSPCs) in the aorta-gonad mesonephros and caudal hematopoietic tissue regions by impairing HSPC proliferation, and consistently downregulated the expression of HSPC genes in K562 cells. This study demonstrates the functions of EPC1/2 in regulating histone H3 acetylation, and in regulating DLST (dihydrolipoamide S-succinyltransferase) via H3 acetylation and cooperating with transcription factors serum response factor and FOXR2 together, and in the subsequent HSPC emergence and proliferation. Our results demonstrate the essential roles of EPC1/2 in regulating H3 acetylation, and DLST as a linkage between EPC1 and EPC2 with mitochondria metabolism, in HSPC emergence and proliferation.

A review of the role of zinc finger proteins on hematopoiesis

The bone marrow is responsible for producing an incredible number of cells daily in order to maintain blood homeostasis through a process called hematopoiesis. Hematopoiesis is a greatly demanding process and one entirely dependent on complex interactions between the hematopoietic stem cell (HSC) and its surrounding microenvironment. Zinc (Zn2+) is considered an important trace element, playing diverse roles in different tissues and cell types, and zinc finger proteins (ZNF) are proteins that use Zn2+ as a structural cofactor. In this way, the ZNF structure is supported by a Zn2+ that coordinates many possible combinations of cysteine and histidine, with the most common ZNF being of the Cys2His2 (C2H2) type, which forms a family of transcriptional activators that play an important role in different cellular processes such as development, differentiation, and suppression, all of these being essential processes for an adequate hematopoiesis. This review aims to shed light on the relationship between ZNF and the regulation of the hematopoietic tissue. We include works with different designs, including both in vitro and in vivo studies, detailing how ZNF might regulate hematopoiesis.

Discovery of N-(2-oxoethyl) sulfanilamide-derived inhibitors of KAT6A (MOZ) against leukemia by an isostere strategy

KAT6A has been identified as a new target for leukemia treatment. The histone acetyltransferase activity of KAT6A is essential for normal hematopoietic stem cell self-renewal, and mutations or translocations are regarded as one of the major causes of leukemia development. In previous studies, CTX-0124143 has been shown to be a class of KAT6A inhibitors with a sulfonyl hydrazide backbone. However, weak activity, poor selectivity and pharmacokinetic problems have hindered its clinical application. In this work, the N‒N bond in compound CTX-0124143 was replaced by an N-C bond, and the aromatic rings were replaced on both sides. Finally, we obtained Compound 6j. Compared to CTX-0124143, 6j showed a 16-fold stronger inhibition of KAT6A (0.49 μM vs. 0.03 μM) with high selectivity. In addition, 6j exhibited strong antitumor activity on four leukemia cell lines. Moreover, 6j showed significant improvement in metabolic stability and pharmacokinetics in vivo and in vitro. In conclusion, 6j shows excellent potential as a promising anti-leukemia drug candidate.

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.

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.

MOZ/ENL complex is a recruiting factor of leukemic AF10 fusion proteins

Changes in the transcriptional machinery cause aberrant self-renewal of non-stem hematopoietic progenitors. AF10 fusions, such as CALM-AF10, are generated via chromosomal translocations, causing malignant leukemia. In this study, we demonstrate that AF10 fusion proteins cause aberrant self-renewal via ENL, which binds to MOZ/MORF lysine acetyltransferases (KATs). The interaction of ENL with MOZ, via its YEATS domain, is critical for CALM-AF10-mediated leukemic transformation. The MOZ/ENL complex recruits DOT1L/AF10 fusion complexes and maintains their chromatin retention via KAT activity. Therefore, inhibitors of MOZ/MORF KATs directly suppress the functions of AF10 fusion proteins, thereby exhibiting strong antitumor effects on AF10 translocation-induced leukemia. Combinatorial inhibition of MOZ/MORF and DOT1L cooperatively induces differentiation of CALM-AF10-leukemia cells. These results reveal roles for the MOZ/ENL complex as an essential recruiting factor of the AF10 fusion/DOT1L complex, providing a rationale for using MOZ/MORF KAT inhibitors in AF10 translocation-induced leukemia.

The histone acetyltransferase KAT6A is recruited to unmethylated CpG islands via a DNA binding winged helix domain

The lysine acetyltransferase KAT6A (MOZ, MYST3) belongs to the MYST family of chromatin regulators, facilitating histone acetylation. Dysregulation of KAT6A has been implicated in developmental syndromes and the onset of acute myeloid leukemia (AML). Previous work suggests that KAT6A is recruited to its genomic targets by a combinatorial function of histone binding PHD fingers, transcription factors and chromatin binding interaction partners. Here, we demonstrate that a winged helix (WH) domain at the very N-terminus of KAT6A specifically interacts with unmethylated CpG motifs. This DNA binding function leads to the association of KAT6A with unmethylated CpG islands (CGIs) genome-wide. Mutation of the essential amino acids for DNA binding completely abrogates the enrichment of KAT6A at CGIs. In contrast, deletion of a second WH domain or the histone tail binding PHD fingers only subtly influences the binding of KAT6A to CGIs. Overexpression of a KAT6A WH1 mutant has a dominant negative effect on H3K9 histone acetylation, which is comparable to the effects upon overexpression of a KAT6A HAT domain mutant. Taken together, our work revealed a previously unrecognized chromatin recruitment mechanism of KAT6A, offering a new perspective on the role of KAT6A in gene regulation and human diseases.

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.

Emerging Roles of Epigenetic Regulators in Maintaining Hematopoietic Stem Cell Homeostasis

Hematopoietic stem cells (HSCs) are adult stem cells with the ability of self-renewal and multilineage differentiation into functional blood cells, thus playing important roles in the homeostasis of hematopoiesis and the immune response. Continuous self-renewal of HSCs offers fresh supplies for the HSC pool, which differentiate into all kinds of mature blood cells, supporting the normal functioning of the entire blood system. Nevertheless, dysregulation of the homeostasis of hematopoiesis is often the cause of many blood diseases. Excessive self-renewal of HSCs leads to hematopoietic malignancies (e.g., leukemia), while deficiency in HSC regeneration results in pancytopenia (e.g., anemia). The regulation of hematopoietic homeostasis is finely tuned, and the rapid development of high-throughput sequencing technologies has greatly boosted research in this field. In this chapter, we will summarize the recent understanding of epigenetic regulators including DNA methylation, histone modification, chromosome remodeling, noncoding RNAs, and RNA modification that are involved in hematopoietic homeostasis, which provides fundamental basis for the development of therapeutic strategies against hematopoietic diseases.

Pantothenate and L-Carnitine Supplementation Improves Pathological Alterations in Cellular Models of KAT6A Syndrome

Mutations in several genes involved in the epigenetic regulation of gene expression have been considered risk alterations to different intellectual disability (ID) syndromes associated with features of autism spectrum disorder (ASD). Among them are the pathogenic variants of the lysine-acetyltransferase 6A (KAT6A) gene, which causes KAT6A syndrome. The KAT6A enzyme participates in a wide range of critical cellular functions, such as chromatin remodeling, gene expression, protein synthesis, cell metabolism, and replication. In this manuscript, we examined the pathophysiological alterations in fibroblasts derived from three patients harboring KAT6A mutations. We addressed survival in a stress medium, histone acetylation, protein expression patterns, and transcriptome analysis, as well as cell bioenergetics. In addition, we evaluated the therapeutic effectiveness of epigenetic modulators and mitochondrial boosting agents, such as pantothenate and L-carnitine, in correcting the mutant phenotype. Pantothenate and L-carnitine treatment increased histone acetylation and partially corrected protein and transcriptomic expression patterns in mutant KAT6A cells. Furthermore, the cell bioenergetics of mutant cells was significantly improved. Our results suggest that pantothenate and L-carnitine can significantly improve the mutant phenotype in cellular models of KAT6A syndrome.

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.

MOZ is critical for the development of MOZ/MLL-fusion-induced leukemia through regulation of Hoxa9/Meis1 expression

Monocytic leukemia zinc finger protein (MOZ, MYST3, or KAT6A) is a MYST-type acetyltransferase involved in chromosomal translocation in acute myelogenous leukemia (AML) and myelodysplastic syndrome. MOZ is established as essential for hematopoiesis; however, the role of MOZ in AML has not been addressed. We propose that MOZ is critical for AML development induced by MLL-AF9, MLL-AF10, or MOZ-TIF2 fusions. Moz-deficient hematopoietic stem/progenitor cells (HSPCs) transduced with an MLL-AF10 fusion gene neither formed colonies in methylcellulose nor induced AML in mice. Moz-deficient HSPCs bearing MLL-AF9 also generated significantly reduced colony and cell numbers. Moz-deficient HSPCs expressing MOZ-TIF2 could form colonies in vitro but could not induce AML in mice. By contrast, Moz was dispensable for colony formation by HOXA9-transduced cells and AML development caused by HOXA9 and MEIS1, suggesting a specific requirement for MOZ in AML induced by MOZ/MLL fusions. Expression of the Hoxa9 and Meis1 genes was decreased in Moz-deficient MLL fusion-expressing cells, while expression of Meis1, but not Hoxa9, was reduced in Moz-deficient MOZ-TIF2 AML cells. AML development induced by MOZ-TIF2 was rescued by introducing Meis1 into Moz-deficient cells carrying MOZ-TIF2. Meis1 deletion impaired MOZ-TIF2–mediated AML development. Active histone modifications were also severely reduced at the Meis1 locus in Moz-deficient MOZ-TIF2 and MLL-AF9 AML cells. These results suggest that endogenous MOZ is critical for MOZ/MLL fusion-induced AML development and maintains active chromatin signatures at target gene loci.

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MOZ is critical for MOZ/MLL fusion-mediated AML development, Meis1 induction by MOZ fusions, and Hoxa9/Meis1 induction by MLL fusions.

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Endogenous MOZ is required to maintain MOZ-target and active histone modifications at the Meis1 gene locus.

Potential Prognostic Markers for Relapsed/Refractory vs. Responsive Acute Myeloid Leukemia

Simple Summary

Acute myeloid leukemia (AML) is the most common blood cancer in the elderly, which progresses rapidly and is often fatal. The prognosis for AML remains poor in most older patients: only about 15% of patients over 60 years of age can recover. Our aim is to determine new potential AML clinical treatment prognosis markers. We analyzed certain genes, proteins and the epigenome profile in therapy-resistant and responsive AML patients at diagnosis stage and after clinical treatment. We determined that MYC, WT1, IDH1, CDKN1A, HDAC2, TET1, KAT6A and GATAD2A gene expression changes might characterize refractory AML. Therefore, these genes could have an impact for AML prognosis.

Abstract

Acute myeloid leukemia (AML) is a heterogeneous disease. A significant proportion of AML patients is refractory to clinical treatment or relapses. Our aim is to determine new potential AML clinical treatment prognosis markers. We investigated various cell fate and epigenetic regulation important gene level differences between refractory and responsive AML patient groups at diagnosis stage and after clinical treatment using RT-qPCR. We demonstrated that oncogenic MYC and WT1 and metabolic IDH1 gene expression was significantly higher and cell cycle inhibitor CDKN1A (p21) gene expression was significantly lower in refractory patients’ bone marrow cells compared to treatment responsive patients both at diagnosis and after clinical treatment. Moreover, we determined that, compared to clinical treatment responsive patients, refractory patients possess a significantly higher gene expression of histone deacetylase 2 (HDAC2) and epigenetic DNA modulator TET1 and a significantly lower gene expression of lysine acetyltransferase 6A (KAT6A) and nucleosome remodeling and deacetylase (NuRD) complex component GATAD2A. We suggest that MYC, WT1, IDH1, CDKN1A, HDAC2, TET1, KAT6A and GATAD2A gene expression changes might characterize refractory AML. Thus, they might be useful for AML prognosis. Additionally, we suggest that epigenetic modulation might be beneficial in combination with standard treatment.

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.

Modulation of cellular processes by histone and non-histone protein acetylation

Lysine acetylation is a widespread and versatile protein post-translational modification. Lysine acetyltransferases and lysine deacetylases catalyse the addition or removal, respectively, of acetyl groups at both histone and non-histone targets. In this Review, we discuss several features of acetylation and deacetylation, including their diversity of targets, rapid turnover, exquisite sensitivity to the concentrations of the cofactors acetyl-CoA, acyl-CoA and NAD⁺, and tight interplay with metabolism. Histone acetylation and non-histone protein acetylation influence a myriad of cellular and physiological processes, including transcription, phase separation, autophagy, mitosis, differentiation and neural function. The activity of lysine acetyltransferases and lysine deacetylases can, in turn, be regulated by metabolic states, diet and specific small molecules. Histone acetylation has also recently been shown to mediate cellular memory. These features enable acetylation to integrate the cellular state with transcriptional output and cell-fate decisions.

miR-143-3p represses leukemia cell proliferation by inhibiting KAT6A expression

The present study is designed to investigate the expressions of microRNA-143-3p (miR-143-3p) and Lysine acetyltransferase 6A (KAT6A) in acute myeloid leukemia (AML) samples and AML cell lines and to explore the possible effects and underlying mechanisms of miR-143-3p on the proliferation of AML cells. The expressions of miR-143-3p and KAT6A in AML samples and cell lines were detected by RT-qPCR assay. CCK-8 and flow cytometry were performed to evaluate the role of KAT6A in viability of AML cells. EdU assay was performed to determine the effects of KAT6A on proliferation of AML cells. Western blot analysis was utilized to assess the impacts of KAT6A on proliferation-related protein expressions of AML cells. ELISA assay was adopted to illustrate the influence of KAT6A on inflammatory responses of AML cells. In addition, the relationship between KAT6A and miR-143-3p was predicted by ENCORI and miRWalk, and confirmed by dual-luciferase reporter assay. Moreover, the effects of KAT6A on the proliferation of AML cells mediated with miR-143-3p were carried out by rescue experiment. The expression of KAT6A was significantly upregulated, while miR-134-4p was downregulated both in the AML tissues and in AML cell lines. In addition, the silence of KAT6A significantly inhibited the viability of AML cells. Besides, KAT6A silencing notably suppressed the proliferation of AML cells and reduced the protein expressions of Ki-67 and PCNA. Knockdown of KAT6A notably decreased the expression levels of IL-1β, TNF-α and IL-6, and increased the expression levels of TGF-β and IL-10. Moreover, overexpression of miR-143-3p repressed viability and proliferation of AML cells and overexpression of KAT6A partially reversed the inhibitory effects of miR-143-3p mimic on viability and proliferation of AML cells. miR-143-3p/KAT6A played an essential role in the viability and proliferation of AML cells.

First case of pan-suture craniosynostosis due to de novo mosaic KAT6A mutation

A nonverbal 3-year-old male with a complex past medical history was referred to pediatric neurosurgery for evaluation of Chiari I malformation. A full clinical evaluation suggested that the "Chiari" was a secondary change caused by craniocerebral disproportion that was the result of delayed pan-sutural craniosynostosis. Given his unknown cause of craniosynostosis, whole-exome sequencing (WES) was performed. WES revealed a de novo, somatic mosaic variant in the KAT6A gene. This report discusses importance of keeping a broad differential in the setting of referral for Chiari I malformation and presents a unique case of craniosynostosis. Additionally, it emphasizes the value of utilizing genetic testing for complex craniofacial cases with unknown causes to provide clinical answers and guide clinical management.

KAT6A and ENL form an epigenetic transcriptional control module to drive critical leukemogenic gene expression programs

Epigenetic programs are dysregulated in acute myeloid leukemia (AML) and help enforce an oncogenic state of differentiation arrest. To identify key epigenetic regulators of AML cell fate, we performed a differentiation-focused CRISPR screen in AML cells. This screen identified the histone acetyltransferase KAT6A as a novel regulator of myeloid differentiation that drives critical leukemogenic gene expression programs. We show that KAT6A is the initiator of a newly-described transcriptional control module in which KAT6A-catalyzed promoter H3K9ac is bound by the acetyllysine reader ENL, which in turn cooperates with a network of chromatin factors to induce transcriptional elongation. Inhibition of KAT6A has strong anti-AML phenotypes in vitro and in vivo, suggesting that KAT6A small molecule inhibitors could be of high therapeutic interest for mono or combinatorial differentiation-based treatment of AML.

The role of MOZ/KAT6A in hematological malignancies and advances in MOZ/KAT6A inhibitors

Hematological malignancies, unlike solid tumors, are a group of malignancies caused by abnormal differentiation of hematopoietic stem cells. Monocytic leukemia zinc finger protein (MOZ), a member of the MYST (MOZ, Ybf2/Sas3, Sas2, Tip60) family, is a histone acetyltransferase. MOZ is involved in various cellular functions: generation and maintenance of hematopoietic stem cells, development of erythroid cells, B-lineage progenitors and myeloid cells, and regulation of cellular senescence. Studies have shown that MOZ is susceptible to translocation in chromosomal rearrangements to form fusion genes, leading to the fusion of MOZ with other cellular regulators to form MOZ fusion proteins. Different MOZ fusion proteins have different roles, such as in the development and progression of hematological malignancies and inhibition of cellular senescence. Thus, MOZ is an attractive target, and targeting MOZ to design small-molecule drugs can help to treat hematological malignancies. This review summarizes recent progress in biology and medicinal chemistry for the histone acetyltransferase MOZ. In the biology section, MOZ and cofactors, structures of MOZ and related HATs, MOZ and fusion proteins, and roles of MOZ in cancer are discussed. In medicinal chemistry, recent developments in MOZ inhibitors are summarized.

A de novo heterozygous variant in KAT6A is associated with a newly named neurodevelopmental disorder Arboleda-Tham syndrome-a case report

Arboleda-Tham syndrome (OMIM#616268) is a newly named neurodevelopmental disorder, which is an autosomal dominant hereditary disease characterized by genetic variants. The clinical manifestations include global developmental delay, primary microcephaly, and craniofacial dysmorphism, as well as more varied features such as feeding difficulties, cardiac defects, and ocular anomalies. Currently, due to restricted knowledge of Arboleda-Tham syndrome and less specific pathological manifestations, it is difficult to diagnose at the early stages of the disease. Here, we present a case with obvious growth retardation and intellectual disability, accompanied by other manifestations including dysmorphic features of the ears, facial dysmorphism, right cryptorchidism, and inguinal hernia. Routine laboratory tests including blood-urine tandem mass spectrometry, urine gas chromatographic mass spectrometry, karyotype, echocardiography, automatic auditory brainstem responses, serum levels of calcium, phosphorus, vitamin D, creatine kinase (CK), and CK isoenzyme (CK-MB), and brain magnetic resonance imaging showed negative results. A de novo heterozygous variant in KAT6A, c.57delA (p.Val20*), was detected by trio-based whole exome sequencing and subsequent validation by Sanger sequencing in the patient, which was absent in both the parents. The patient received rehabilitation and nutritional intervention. The testis reduction and orchiopexy was scheduled when he was 1 year old. Our report extends the phenotype-genotype map of Arboleda-Tham syndrome, and also expands the mutant spectrum of the KAT6A gene. Moreover, this case emphasizes the timely conduction of whole exome sequencing for the early diagnosis of Arboleda-Tham syndrome, and spares patients from meaningless examinations and ineffective treatments.

Histone Acetyltransferases and Stem Cell Identity

Acetylation of histones is a key epigenetic modification involved in transcriptional regulation. The addition of acetyl groups to histone tails generally reduces histone-DNA interactions in the nucleosome leading to increased accessibility for transcription factors and core transcriptional machinery to bind their target sequences. There are approximately 30 histone acetyltransferases and their corresponding complexes, each of which affect the expression of a subset of genes. Because cell identity is determined by gene expression profile, it is unsurprising that the HATs responsible for inducing expression of these genes play a crucial role in determining cell fate. Here, we explore the role of HATs in the maintenance and differentiation of various stem cell types. Several HAT complexes have been characterized to play an important role in activating genes that allow stem cells to self-renew. Knockdown or loss of their activity leads to reduced expression and or differentiation while particular HATs drive differentiation towards specific cell fates. In this study we review functions of the HAT complexes active in pluripotent stem cells, hematopoietic stem cells, muscle satellite cells, mesenchymal stem cells, neural stem cells, and cancer stem cells.

Roles of the MYST Family in the Pathogenesis of Alzheimer's Disease via Histone or Non-histone Acetylation

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases and a major cause of death among elderly individuals. The etiology of AD involves a combination of genetic, environmental, and lifestyle factors. A number of epigenetic alterations in AD have recently been reported; for example, studies have found an increase in histone acetylation in patients with AD and the protective function of histone deacetylase inhibitors. The histone acetylases in the MYST family are involved in a number of key nuclear processes, such as gene-specific transcriptional regulation, DNA replication, and DNA damage response. Therefore, it is not surprising that they contribute to epigenetic regulation as an intermediary between genetic and environmental factors. MYST proteins also exert acetylation activity on non-histone proteins that are closely associated with the pathogenesis of AD. In this review, we summarized the current understanding of the roles of MYST acetyltransferases in physiological functions and pathological processes related to AD. Additionally, using published RNA-seq, ChIP-seq, and ChIP-chip data, we identified enriched pathways to further evaluate the correlation between MYST and AD. The recent research described in this review supports the importance of epigenetic modifications and the MYST family in AD, providing a basis for future functional studies.

Impaired Regulation of Histone Methylation and Acetylation Underlies Specific Neurodevelopmental Disorders

Epigenetic processes are critical for governing the complex spatiotemporal patterns of gene expression in neurodevelopment. One such mechanism is the dynamic network of post-translational histone modifications that facilitate recruitment of transcription factors or even directly alter chromatin structure to modulate gene expression. This is a tightly regulated system, and mutations affecting the function of a single histone-modifying enzyme can shift the normal epigenetic balance and cause detrimental developmental consequences. In this review, we will examine select neurodevelopmental conditions that arise from mutations in genes encoding enzymes that regulate histone methylation and acetylation. The methylation-related conditions discussed include Wiedemann-Steiner, Kabuki, and Sotos syndromes, and the acetylation-related conditions include Rubinstein-Taybi, KAT6A, genitopatellar/Say-Barber-Biesecker-Young-Simpson, and brachydactyly mental retardation syndromes. In particular, we will discuss the clinical/phenotypic and genetic basis of these conditions and the model systems that have been developed to better elucidate cellular and systemic pathological mechanisms.

Epigenetic modifiers in normal and aberrent erythropoeisis

Erythroid differentiation program is comprised of lineage commitment, erythroid progenitor proliferation, and termination differentiation. Each stage of the differentiation program is heavily influenced by epigenetic modifiers that alter the epigenome in a dynamic fashion influenced by cytokines/humeral factors and are amicable to target by drugs. The epigenetic modifiers can be classified as DNA modifiers (DNMT, TET), mRNA modifiers (RNA methylases and demethylases) and histone protein modifiers (methyltransferases, acetyltransferases, demethylases, and deacetylases). Here we describe mechanisms by which these epigenetic modifiers influence and guide erythroid-lineage differentiation during normal and malignant erythropoiesis and also benign diseases that arise from their altered structure or function.

Downregulation of the GHRH/GH/IGF1 axis in a mouse model of Börjeson-Forssman-Lehman syndrome

Börjeson-Forssman-Lehmann syndrome (BFLS) is an intellectual disability and endocrine disorder caused by plant homeodomain finger 6 (PHF6) mutations. Individuals with BFLS present with short stature. We report a mouse model of BFLS, in which deletion of Phf6 causes a proportional reduction in body size compared with control mice. Growth hormone (GH) levels were reduced in the absence of PHF6. Phf6 ^{- /Y} animals displayed a reduction in the expression of the genes encoding GH-releasing hormone (GHRH) in the brain, GH in the pituitary gland and insulin-like growth factor 1 (IGF1) in the liver. Phf6 deletion specifically in the nervous system caused a proportional growth defect, indicating a neuroendocrine contribution to the phenotype. Loss of suppressor of cytokine signaling 2 (SOCS2), a negative regulator of growth hormone signaling partially rescued body size, supporting a reversible deficiency in GH signaling. These results demonstrate that PHF6 regulates the GHRH/GH/IGF1 axis.

The key roles of the lysine acetyltransferases KAT6A and KAT6B in physiology and pathology

Histone modifications and more specifically ε-lysine acylations are key epigenetic regulators that control chromatin structure and gene transcription, thereby impacting on various important cellular processes and phenotypes. Furthermore, lysine acetylation of many non-histone proteins is involved in key cellular processes including transcription, DNA damage repair, metabolism, cellular proliferation, mitosis, signal transduction, protein folding, and autophagy. Acetylation affects protein functions through multiple mechanisms including regulation of protein stability, enzymatic activity, subcellular localization, crosstalk with other post-translational modifications as well as regulation of protein-protein and protein-DNA interactions. The paralogous lysine acetyltransferases KAT6A and KAT6B which belong to the MYST family of acetyltransferases, were first discovered approximately 25 years ago. KAT6 acetyltransferases acylate both histone H3 and non-histone proteins. In this respect, KAT6 acetyltransferases play key roles in regulation of transcription, various developmental processes, maintenance of hematopoietic and neural stem cells, regulation of hematopoietic cell differentiation, cell cycle progression as well as mitosis. In the current review, we discuss the physiological functions of the acetyltransferases KAT6A and KAT6B as well as their functions under pathological conditions of aberrant expression, leading to several developmental syndromes and cancer. Importantly, both upregulation and downregulation of KAT6 proteins was shown to play a role in cancer formation, progression, and therapy resistance, suggesting that they can act as oncogenes or tumor suppressors. We also describe reciprocal regulation of expression between KAT6 proteins and several microRNAs as well as their involvement in cancer formation, progression and resistance to therapy.

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.

Chromatin-Remodeled State in Lymphoma

PURPOSE OF REVIEW

Emerging evidence has shown that epigenetic derangements might drive and promote tumorigenesis in various types of malignancies and is prevalent in both B cell and T cell lymphomas. The purpose of this review is to explain how the epigenetic derangements result in a chromatin-remodeled state in lymphoma and contribute to the biology and clinical features of these tumors.

RECENT FINDINGS

Studies have explored on the functional role of epigenetic derangements in chromatin remodeling and lymphomagenesis. For example, the haploinsufficiency of CREBBP facilitates malignant transformation in mice and directly implicates the importance to re-establish the physiologic acetylation level. New findings identified 4 prominent DLBCL subtypes, including EZB-GC-DLBCL subtype that enriched in mutations of CREBBP, EP300, KMT2D, and SWI/SNF complex genes. EZB subtype has a worse prognosis than other GCB-tumors. Moreover, the action of the histone modifiers as well as chromatin-remodeling factors (e.g., SWI/SNF complex) cooperates to influence the chromatin state resulting in transcription repression. Drugs that alter the epigenetic landscape have been approved in T cell lymphoma. In line with this finding, epigenetic lesions in histone modifiers have recently been uncovered in this disease, further confirming the vulnerability to the therapies targeting epigenetic derangements. Modulating the chromatin state by epigenetic-modifying agents provides precision-medicine opportunities to patients with lymphomas that depend on this biology.

Discovery of Acylsulfonohydrazide-Derived Inhibitors of the Lysine Acetyltransferase, KAT6A, as Potent Senescence-Inducing Anti-Cancer Agents

A high-throughput screen designed to discover new inhibitors of histone acetyltransferase KAT6A uncovered CTX-0124143 (1), a unique aryl acylsulfonohydrazide with an IC₅₀ of 1.0 μM. Using this acylsulfonohydrazide as a template, we herein disclose the results of our extensive structure-activity relationship investigations, which resulted in the discovery of advanced compounds such as 55 and 80. These two compounds represent significant improvements on our recently reported prototypical lead WM-8014 (3) as they are not only equivalently potent as inhibitors of KAT6A but are less lipophilic and significantly more stable to microsomal degradation. Furthermore, during this process, we discovered a distinct structural subclass that contains key 2-fluorobenzenesulfonyl and phenylpyridine motifs, culminating in the discovery of WM-1119 (4). This compound is a highly potent KAT6A inhibitor (IC₅₀ = 6.3 nM; K_D = 0.002 μM), competes with Ac-CoA by binding to the Ac-CoA binding site, and has an oral bioavailability of 56% in rats.

Genome-wide identification, structural analysis and expression profiles of GRAS gene family in orchardgrass

The GRAS gene family is a family of transcription factors that regulates plant growth and development. Despite being well-studied in many plant species, little is known about this gene family in orchardgrass (Dactylis glomerata L.), one of the top four economically important perennial forage grasses cultivated worldwide. We identified 46 GRAS genes in orchardgrass and analyzed their characteristics by phylogenetic, gene structural, motifs and expression patterns analysis. The phylogenetic analysis of eight species revealed that DgGRAS family had the evolutional conservation and closer homology relationship with the GRAS family of rice, barley and Brachypodium distachyon. Moreover, 46 DgGRAS proteins were divided into eight subfamilies based on the tree topology and rice or Arabidopsis classification, and LISCL subfamily was the largest one. Besides, we found that the motif 15 may be unique to the orchardgrass LISCL subfamily, and the motif 6 and motif 17 had indispensable functions in the orchardgrass LISCL subfamily. We further analyzed the expression profiles of DgGRAS genes at mature and seeding stage. And we found that DgGRAS17 played an important role in the growth and development no matter what stage it was at. DgGRAS5, DgGRAS28, DgGRAS31, DgGRAS42 and DgGRAS44 got involved in processes of the growth and development at seeding stage instead of mature stage. These results indicated that the major expression patterns and detailed functions of the DgGRAS genes varied with developmental stages. Taken together, this is the first systematic analysis of the GRAS gene family in the orchardgrass genome and the results provide insights into the potential functions of GRAS genes.

Biological Functions of the ING Proteins

The proteins belonging to the inhibitor of growth (ING) family of proteins serve as epigenetic readers of the H3K4Me3 histone mark of active gene transcription and target histone acetyltransferase (HAT) or histone deacetylase (HDAC) protein complexes, in order to alter local chromatin structure. These multidomain adaptor proteins interact with numerous other proteins to facilitate their localization and the regulation of numerous biochemical pathways that impinge upon biological functions. Knockout of some of the ING genes in murine models by various groups has verified their status as tumor suppressors, with ING1 knockout resulting in the formation of large clear-cell B-lymphomas and ING2 knockout increasing the frequency of ameloblastomas, among other phenotypic effects. ING4 knockout strongly affects innate immunity and angiogenesis, and INGs1, ING2, and ING4 have been reported to affect apoptosis in different cellular models. Although ING3 and ING5 knockouts have yet to be published, preliminary reports indicate that ING3 knockout results in embryonic lethality and that ING5 knockout may have postpartum effects on stem cell maintenance. In this review, we compile the known information on the domains of the INGs and the effects of altering ING protein expression, to better understand the functions of this adaptor protein family and its possible uses for targeted cancer therapy.

Epigenetic regulation of hematopoietic stem cell homeostasis

As one of the best characterized adult stem cells, hematopoietic stem cell (HSC) homeostasis is of great importance to hematopoiesis and immunity due to HSC's abilities of self-renewal and multi-lineage differentiation into functional blood cells. However, excessive self-renewal of HSCs can lead to severe hematopoietic malignancies like leukemia, whereas deficient self-renewal of HSCs may result in HSC exhaustion and eventually apoptosis of specialized cells, giving rise to abnormalities such as immunodeficiency or anemia. How HSC homeostasis is maintained has been studied for decades and regulatory factors can be generally categorized into two classes: genetic factors and epigenetic factors. Although genetic factors such as signaling pathways or transcription factors have been well explored, recent studies have emerged the indispensable roles of epigenetic factors. In this review, we have summarized regulatory mechanisms of HSC homeostasis by epigenetic factors, including DNA methylation, histone modification, chromatin remodeling, non-coding RNAs, and RNA modification, which will facilitate applications such as HSC ex vivo expansion and exploration of novel therapeutic approaches for many hematological diseases.

MOZ directs the distal-less homeobox gene expression program during craniofacial development

Oral clefts are common birth defects. Individuals with oral clefts who have identical genetic mutations regularly present with variable penetrance and severity. Epigenetic or chromatin-mediated mechanisms are commonly invoked to explain variable penetrance. However, specific examples of these are rare. Two functional copies of the MOZ (KAT6A, MYST3) gene, encoding a MYST family lysine acetyltransferase chromatin regulator, are essential for human craniofacial development, but the molecular role of MOZ in this context is unclear. Using genetic interaction and genomic studies, we have investigated the effects of loss of MOZ on the gene expression program during mouse development. Among the more than 500 genes differentially expressed after loss of MOZ, 19 genes had previously been associated with cleft palates. These included four distal-less homeobox (DLX) transcription factor-encoding genes, Dlx1, Dlx2, Dlx3 and Dlx5 and DLX target genes (including Barx1, Gbx2, Osr2 and Sim2). MOZ occupied the Dlx5 locus and was required for normal levels of histone H3 lysine 9 acetylation. MOZ affected Dlx gene expression cell-autonomously within neural crest cells. Our study identifies a specific program by which the chromatin modifier MOZ regulates craniofacial development.

The many lives of KATs - detectors, integrators and modulators of the cellular environment

Research over the past three decades has firmly established lysine acetyltransferases (KATs) as central players in regulating transcription. Recent advances in genomic sequencing, metabolomics, animal models and mass spectrometry technologies have uncovered unexpected new roles for KATs at the nexus between the environment and transcriptional regulation. Thousands of reversible acetylation sites have been mapped in the proteome that respond dynamically to the cellular milieu and maintain major processes such as metabolism, autophagy and stress response. Concurrently, researchers are continuously uncovering how deregulation of KAT activity drives disease, including cancer and developmental syndromes characterized by severe intellectual disability. These novel findings are reshaping our view of KATs away from mere modulators of chromatin to detectors of the cellular environment and integrators of diverse signalling pathways with the ability to modify cellular phenotype.

Are transplantable stem cells required for adult hematopoiesis?

Hematopoietic stem cells (HSCs) have been studied intensely for more than half a century. As a result, the properties of HSCs have become a paradigm of adult stem cell biology and function. The "classical" view of hematopoiesis suggests that the HSCs sit at the top of a hierarchy and that differentiation involves sequential production of multipotent and lineage committed progenitors with limited self-renewal capacity. This view of hematopoiesis is certainly valid after transplantation of HSCs, where, with appropriate support, a single HSC can regenerate the entire hematopoietic system of the recipient. However, it is not clear whether HSCs perform the same function during steady-state hematopoiesis. Indeed, studies have shown that the majority of classical HSCs are not required for ongoing steady-state adult hematopoiesis. Several reports suggest that steady-state hematopoiesis relies on highly proliferative cells with more lineage restricted characteristics, a finding that was not anticipated based on results from transplantation experiments. However, other studies indicate a more substantial HSC contribution. Nevertheless, the notion of HSCs as distinct from progenitors appears to be simplistic in view of ample evidence for heterogeneity within the stem cell compartment. In this review we discuss recent results and controversies surrounding HSCs.

KAT6A Syndrome: genotype-phenotype correlation in 76 patients with pathogenic KAT6A variants

PURPOSE

Pathogenic variants in KAT6A have recently been identified as a cause of syndromic developmental delay. Within 2 years, the number of patients identified with pathogenic KAT6A variants has rapidly expanded and the full extent and variability of the clinical phenotype has not been reported.

METHODS

We obtained data for patients with KAT6A pathogenic variants through three sources: treating clinicians, an online family survey distributed through social media, and a literature review.

RESULTS

We identified 52 unreported cases, bringing the total number of published cases to 76. Our results expand the genotypic spectrum of pathogenic variants to include missense and splicing mutations. We functionally validated a pathogenic splice-site variant and identified a likely hotspot location for de novo missense variants. The majority of clinical features in KAT6A syndrome have highly variable penetrance. For core features such as intellectual disability, speech delay, microcephaly, cardiac anomalies, and gastrointestinal complications, genotype- phenotype correlations show that late-truncating pathogenic variants (exons 16-17) are significantly more prevalent. We highlight novel associations, including an increased risk of gastrointestinal obstruction.

CONCLUSION

Our data expand the genotypic and phenotypic spectrum for individuals with genetic pathogenic variants in KAT6A and we outline appropriate clinical management.

Emerging Role of Histone Acetyltransferase in Stem Cells and Cancer

Protein acetylation is one of the most important posttranslational modifications catalyzed by acetyltransferases and deacetylases, through the addition and removal of acetyl groups to lysine residues. Lysine acetylation can affect protein-nucleic acid or protein-protein interactions and protein localization, transport, stability, and activity. It regulates the function of a large variety of proteins, including histones, oncoproteins, tumor suppressors, and transcription factors, thus representing a crucial regulator of several biological processes with particular prominent roles in transcription and metabolism. Thus, it is unsurprising that alteration of protein acetylation is involved in human disease, including metabolic disorders and cancers. In this context, different hematological and solid tumors are characterized by deregulation of the protein acetylation pattern as a result of genetic or epigenetic changes. The imbalance between acetylation and deacetylation of histone or nonhistone proteins is also involved in the modulation of the self-renewal and differentiation ability of stem cells, including cancer stem cells. Here, we summarize a combination of in vitro and in vivo studies, undertaken on a set of acetyltransferases, and discuss the physiological and pathological roles of this class of enzymes. We also review the available data on the involvement of acetyltransferases in the regulation of stem cell renewal and differentiation in both normal and cancer cell population.

Histone Lysine and Genomic Targets of Histone Acetyltransferases in Mammals

Histone acetylation has been recognized as an important post-translational modification of core nucleosomal histones that changes access to the chromatin to allow gene transcription, DNA replication, and repair. Histone acetyltransferases were initially identified as co-activators that link DNA-binding transcription factors to the general transcriptional machinery. Over the years, more chromatin-binding modes have been discovered suggesting direct interaction of histone acetyltransferases and their protein complex partners with histone proteins. While much progress has been made in characterizing histone acetyltransferase complexes biochemically, cell-free activity assay results are often at odds with in-cell histone acetyltransferase activities. In-cell studies suggest specific histone lysine targets, but broad recruitment modes, apparently not relying on specific DNA sequences, but on chromatin of a specific functional state. Here we review the evidence for general versus specific roles of individual nuclear lysine acetyltransferases in light of in vivo and in vitro data in the mammalian system.

Inhibitors of histone acetyltransferases KAT6A/B induce senescence and arrest tumour growth

Acetylation of histones by lysine acetyltransferases (KATs) is essential for chromatin organization and function¹. Among the genes coding for the MYST family of KATs (KAT5-KAT8) are the oncogenes KAT6A (also known as MOZ) and KAT6B (also known as MORF and QKF)^2,3. KAT6A has essential roles in normal haematopoietic stem cells^4-6 and is the target of recurrent chromosomal translocations, causing acute myeloid leukaemia^7,8. Similarly, chromosomal translocations in KAT6B have been identified in diverse cancers⁸. KAT6A suppresses cellular senescence through the regulation of suppressors of the CDKN2A locus^9,10, a function that requires its KAT activity¹⁰. Loss of one allele of KAT6A extends the median survival of mice with MYC-induced lymphoma from 105 to 413 days¹¹. These findings suggest that inhibition of KAT6A and KAT6B may provide a therapeutic benefit in cancer. Here we present highly potent, selective inhibitors of KAT6A and KAT6B, denoted WM-8014 and WM-1119. Biochemical and structural studies demonstrate that these compounds are reversible competitors of acetyl coenzyme A and inhibit MYST-catalysed histone acetylation. WM-8014 and WM-1119 induce cell cycle exit and cellular senescence without causing DNA damage. Senescence is INK4A/ARF-dependent and is accompanied by changes in gene expression that are typical of loss of KAT6A function. WM-8014 potentiates oncogene-induced senescence in vitro and in a zebrafish model of hepatocellular carcinoma. WM-1119, which has increased bioavailability, arrests the progression of lymphoma in mice. We anticipate that this class of inhibitors will help to accelerate the development of therapeutics that target gene transcription regulated by histone acetylation.

Acetylation of the Cd8 Locus by KAT6A Determines Memory T Cell Diversity

How functionally diverse populations of pathogen-specific killer T cells are generated during an immune response remains unclear. Here, we propose that fine-tuning of CD8αβ co-receptor levels via histone acetylation plays a role in lineage fate. We show that lysine acetyltransferase 6A (KAT6A) is responsible for maintaining permissive Cd8 gene transcription and enabling robust effector responses during infection. KAT6A-deficient CD8(+) T cells downregulated surface CD8 co-receptor expression during clonal expansion, a finding linked to reduced Cd8α transcripts and histone-H3 lysine 9 acetylation of the Cd8 locus. Loss of CD8 expression in KAT6A-deficient T cells correlated with reduced TCR signaling intensity and accelerated contraction of the effector-like memory compartment, whereas the long-lived memory compartment appeared unaffected, a result phenocopied by the removal of the Cd8 E8I enhancer element. These findings suggest a direct role of CD8αβ co-receptor expression and histone acetylation in shaping functional diversity within the cytotoxic T cell pool.

PzTAC and PzLAZY from a narrow-crown poplar contribute to regulation of branch angles

Plant architecture, as a basic element influenced by genetic and environmental factors, has an important effect on grain yield via light transmission in agroforestry systems. The molecular mechanism underlying control of branch angle, an important aspect of tree architecture, is not well understood in poplars. Here, we cloned two genes from Populus × zhaiguanheibaiyang (a narrow-crown poplar), designated PzTAC and PzLAZY, which were predicted to be members of the ITG gene family through sequence homology. Transcript levels of the homologous genes were estimated by reverse transcriptase quantitative PCR (RT-qPCR) in different organs of P. × zhaiguanheibaiyang and P. Deltoides 'Zhonglin2025' (a broad-crown poplar). TAC expression was mainly confined to the leaves and annual shoots, whereas LAZY was mainly expressed in the annual shoots and axillary buds. Beside, we detected the promoter expression patterns derived from the PzTAC and PzLAZY genes using the β-glucuronidase (GUS) reporter gene in transgenic Populus × euramericana 'Neva'. GUS activity driven by the PzTAC and PzLAZY promoters was detected in mature leaves, leaf axils and vascular tissues of roots. The PzTAC promoter was mainly active in leaf veins, whereas the PzLAZY promoter was mainly active in mesophyll cells and root tips. The average branch angle in transgenic 35S::PzTAC plants was larger than that of transgenic 35S::PzLAZY plants. The results provide strong evidence that the two genes affect the vascular tissues of transgenic plants to modify branch angles.