Targeting UBE4A Revives Viperin Protein in Epithelium to Enhance Host Antiviral Defense.

Mutation and prevalence of pathogenic viruses prompt the development of broad-spectrum antiviral strategies. Viperin is a potent antiviral protein that inhibits a broad range of viruses. Unexpectedly, we found that Viperin protein production in epithelium is defective in response to both viruses and interferons (IFNs). We further revealed that viruses and IFNs stimulate expression of the acetyltransferase HAT1, which induces Lys197-acetylation on Viperin. Viperin acetylation in turn recruits UBE4A that stimulates K6-linked polyubiquitination at Lys206 of Viperin, leading to Viperin protein degradation. Importantly, UBE4A deficiency restores Viperin protein production in epithelium. We then designed interfering peptides (IPs) to inhibit UBE4A binding with Viperin. We found that VIP-IP3 rescues Viperin protein production in epithelium and therefore enhances cellular antiviral activity. VIP-IP3 renders mice more resistant to viral infection. These findings could provide strategies for both enhancing host broad-spectrum antiviral response and improving the efficacy of IFN-based antiviral therapy.

HAT1 Coordinates Histone Production and Acetylation via H4 Promoter Binding.

The energetic costs of duplicating chromatin are large and therefore likely depend on nutrient sensing checkpoints and metabolic inputs. By studying chromatin modifiers regulated by epithelial growth factor, we identified histone acetyltransferase 1 (HAT1) as an induced gene that enhances proliferation through coordinating histone production, acetylation, and glucose metabolism. In addition to its canonical role as a cytoplasmic histone H4 acetyltransferase, we isolated a HAT1-containing complex bound specifically at promoters of H4 genes. HAT1-dependent transcription of H4 genes required an acetate-sensitive promoter element. HAT1 expression was critical for S-phase progression and maintenance of H3 lysine 9 acetylation at proliferation-associated genes, including histone genes. Therefore, these data describe a feedforward circuit whereby HAT1 captures acetyl groups on nascent histones and drives H4 production by chromatin binding to support chromatin replication and acetylation. These findings have important implications for human disease, since high HAT1 levels associate with poor outcomes across multiple cancer types.

Prognostic Value of Histone Acetyl Transferase 1 (HAT-1) and Inflammatory Signatures in Pancreatic Cancer.

Pancreatic cancer is a type of gastrointestinal tumor with a growing incidence and mortality worldwide. Pancreatic ductal adenocarcinoma (PDAC) constitutes 90% of cases, and late-stage diagnosis is common, leading to a 5-year survival rate of less than 10% in high-income countries. The use of biomarkers has different proven translational applications, facilitating early diagnosis, accurate prognosis and identification of potential therapeutic targets. Several studies have shown a correlation between the tissue expression levels of various molecules, measured through immunohistochemistry (IHC), and survival rates in PDAC. Following the hallmarks of cancer, epigenetic and metabolic reprogramming, together with immune evasion and tumor-promoted inflammation, plays a critical role in cancer initiation and development. In this study, we aim to explore via IHC and Kaplan-Meier analyses the prognostic value of various epigenetic-related markers (histones 3 and 4 (H3/H4), histone acetyl transferase 1 (HAT-1), Anti-Silencing Function 1 protein (ASF1), Nuclear Autoantigenic Sperm Protein (NASP), Retinol Binding Protein 7 (RBBP7), importin 4 (IPO4) and IPO5), metabolic regulators (Phosphoglycerate mutase (PGAM)) and inflammatory mediators (allograft inflammatory factor 1 (AIF-1), interleukin 10 (IL-10), IL-12A and IL-18) in patients with PDAC. Also, through a correlation analysis, we have explored the possible interconnections in the expression levels of these molecules. Our results show that higher expression levels of these molecules are directly associated with poorer survival rates in PDAC patients, except in the case of IL-10, which shows an inverse association with mortality. HAT1 was the molecule more clearly associated with mortality, with a hazard risk of 21.74. The correlogram demonstrates an important correlation between almost all molecules studied (except in the case of IL-18), highlighting potential interactions between these molecules. Overall, our study demonstrates the relevance of including different markers from IHC techniques in order to identify unexplored molecules to develop more accurate prognosis methods and possible targeted therapies. Additionally, our correlation analysis reveals potential interactions among these markers, offering insights into PDAC's pathogenesis and paving the way for targeted therapies tailored to individual patient profiles. Future studies should be conducted to confirm the prognostic value of these components in PDAC in a broader sample size, as well as to evaluate the possible biological networks connecting them.

Bevacizumab induces ferroptosis and enhances CD8+ T cell immune activity in liver cancer via modulating HAT1 and increasing IL-9.

Bevacizumab is a recombinant humanized monoclonal immunoglobulin (Ig) G1 antibody of VEGF, and inhibits angiogenesis and tumor growth in hepatocellular carcinoma (HCC). Ferroptosis, a new form of regulated cell death function independently of the apoptotic machinery, has been accepted as an attractive target for pharmacological intervention; the ferroptosis pathway can enhance cell immune activity of anti-PD1 immunotherapy in HCC. In this study we investigated whether and how bevacizumab regulated ferroptosis and immune activity in liver cancer. Firstly, we performed RNA-sequencing in bevacizumab-treated human liver cancer cell line HepG2 cells, and found that bevacizumab significantly altered the expression of a number of genes including VEGF, PI3K, HAT1, SLC7A11 and IL-9 in liver cancer, bevacizumab upregulated 37 ferroptosis-related drivers, and downregulated 17 ferroptosis-related suppressors in particular. We demonstrated that bevacizumab triggered ferroptosis in liver cancer cells by driving VEGF/PI3K/HAT1/SLC7A11 axis. Clinical data confirmed that the expression levels of VEGF were positively associated with those of PI3K, HAT1 and SLC7A11 in HCC tissues. Meanwhile, we found that bevacizumab enhanced immune cell activity in tumor immune-microenvironment. We identified that HAT1 up-regulated miR-143 targeting IL-9 mRNA 3'UTR in liver cancer cells; bevacizumab treatment resulted in the increase of IL-9 levels and its secretion via VEGF/PI3K/HAT1/miR-143/IL-9 axis, which led to the inhibition of tumor growth in vivo through increasing the release of IL-2 and Granzyme B from activated CD8+ T cells. We conclude that in addition to inhibiting angiogenesis, bevacizumab induces ferroptosis and enhances CD8+ T cell immune activity in liver cancer. This study provides new insight into the mechanisms by which bevacizumab synergistically modulates ferroptosis and CD8+ T cell immune activity in liver cancer.

Involvement of Histone Acetyltransferase 1 (HAT1) in the Spermatogenesis of Non-Condensed Nuclear Sperm in Chinese Mitten Crab, Eriocheir sinensis.

Chinese mitten crab, Eriocheir sinensis, is a decapod crustacean with a special, non-condensated nucleus in the sperm. Studies have shown that the nuclear compact state of male germ cells during the spermatogenesis is closely related to histone modification. To explore the possible role of histone acetyltransferase 1 (HAT1) in the chromatin organization during the E. sinensis spermatogenesis, we took the testis tissues of both adult and juvenile crabs as the materials of study and analyzed the biological functions of HAT1 by whole transcriptome sequencing and bioinformatics, then further analyzed the expression and distribution of HAT1 using the methods of RT-qRCR, western blotting, and immunofluorescence location. The results showed that HAT1 is an alkaline-unstable hydrophilic protein. It was predicted to interact with a variety of histones and chromosome assembly proteins, including Asf1b, Chaf1b, and Hist1h3f, and is involved in many biological functions pertaining to chromatin dynamics such as chromatin organization, DNA dependent nucleosome assembly, DNA conformational changes, and so on. HAT1 was up-regulated in the adult testes compared to the juvenile (n = 3, P < 0.05). HAT1 was mainly located in the nuclei of male germ cells of E. sinensis. As spermatogenesis proceeded, the expression of HAT1 decreased and even disappeared in the nuclei (n = 3, P < 0.05). HAT1 is an important player in histone acetylation, which facilitates chromatin alteration in a three-dimensional conformation. The expression of HAT1 in different male germ cells might indicate the chromatin dynamics at the diversity stages of spermatogenesis. The high expression of HAT1 at the early stages of E. sinensis spermatogenesis hints the active involvement in chromatin organization, while its progressively reduced expression accompanied by the progression of spermatogenesis suggests a relatively gradual stabilization and stereotyping of chromatin. As for the disappearance of HAT1 in mature sperm with non-condensed nuclei, the reduction in histones targeted by HAT1 or histone acetylation may be an important initiator.

HBV confers innate immune evasion through triggering HAT1/acetylation of H4K5/H4K12/miR-181a-5p or KPNA2/cGAS-STING/IFN-I signaling.

Viral immune evasion is crucial to the pathogenesis of hepatitis B virus (HBV) infection. However, the role of HBV in the modulation of innate immune evasion is poorly understood. A liver-specific histone acetyltransferase 1 (Hat1) knockout (KO) mouse model and HAT1 KO cell line were established. Immunohistochemistry staining, Western blot analysis, Southern blot analysis, Northern blot analysis, immunofluorescence assays, enzyme-linked immunosorbent assay, reverse transcription-quantitative polymerase chain reaction, and chromatin immunoprecipitation assays were performed in the livers of mouse models, primary human hepatocytes, HepG2-NTCP, and Huh7 and HepG2 cell lines. HBV-elevated HAT1 increased the expression of miR-181a-5p targeting cyclic GMP-AMP synthase (cGAS) messenger RNA 3' untranslated regions through modulating acetylation of H4K5 and H4K12 in vitro and in vivo, leading to the inability of cGAS-stimulator of interferon genes (STING) pathway and type I interferon (IFN-I) signaling. Additionally, HBV-elevated HAT1 promoted the expression of KPNA2 through modulating acetylation of H4K5 and H4K12 in the system, resulting in nuclear translocation of cGAS, HBx was responsible for the events by HAT1, suggesting that HBV-elevated HAT1 controls the cGAS-STING pathway and IFN-I signaling to modulate viral innate immune evasion. HBV confers innate immune evasion through triggering HAT1/acetylation of H4K5/H4K12/miR-181a-5p or KPNA2/cGAS-STING/IFN-I signaling. Our finding provides new insights into the mechanism by which HBV drives viral innate immune evasion.

Decreased HAT1 expression in granulosa cells disturbs oocyte meiosis during mouse ovarian aging.

BACKGROUND: With advanced maternal age, abnormalities during oocyte meiosis increase significantly. Aneuploidy is an important reason for the reduction in the quality of aged oocytes. However, the molecular mechanism of aneuploidy in aged oocytes is far from understood. Histone acetyltransferase 1 (HAT1) has been reported to be essential for mammalian development and genome stability, and involved in multiple organ aging. Whether HAT1 is involved in ovarian aging and the detailed mechanisms remain to be elucidated. METHODS: The level of HAT1 in aged mice ovaries was detected by immunohistochemical and immunoblotting. To explore the function of HAT1 in the process of mouse oocyte maturation, we used Anacardic Acid (AA) and small interfering RNAs (siRNA) to culture cumulus-oocyte complexes (COCs) from ICR female mice in vitro and gathered statistics of germinal vesicle breakdown (GVBD), the first polar body extrusion (PBE), meiotic defects, aneuploidy, 2-cell embryos formation, and blastocyst formation rate. Moreover, the human granulosa cell (GC)-like line KGN cells were used to investigate the mechanisms of HAT1 in this progress. RESULTS: HAT1 was highly expressed in ovarian granulosa cells (GCs) from young mice and the expression of HAT1 was significantly decreased in aged GCs. AA and siRNAs mediated inhibition of HAT1 in GCs decreased the PBE rate, and increased meiotic defects and aneuploidy in oocytes. Further studies showed that HAT1 could acetylate Forkhead box transcription factor O1 (FoxO1), leading to the translocation of FoxO1 into the nucleus. Resultantly, the translocation of acetylated FoxO1 increased the expression of amphiregulin (AREG) in GCs, which plays a significant role in oocyte meiosis. CONCLUSION: The present study suggests that decreased expression of HAT1 in GCs is a potential reason corresponding to oocyte age-related meiotic defects and provides a potential therapeutic target for clinical intervention to reduce aneuploid oocytes.

Histone acetyltransferase 1 is a succinyltransferase for histones and non-histones and promotes tumorigenesis.

Lysine succinylation (Ksucc) is an evolutionarily conserved and widespread post-translational modification. Histone acetyltransferase 1 (HAT1) is a type B histone acetyltransferase, regulating the acetylation of both histone and non-histone proteins. However, the role of HAT1 in succinylation modulation remains unclear. Here, we employ a quantitative proteomics approach to study succinylation in HepG2 cancer cells and find that HAT1 modulates lysine succinylation on various proteins including histones and non-histones. HAT1 succinylates histone H3 on K122, contributing to epigenetic regulation and gene expression in cancer cells. Moreover, HAT1 catalyzes the succinylation of PGAM1 on K99, resulting in its increased enzymatic activity and the stimulation of glycolytic flux in cancer cells. Clinically, HAT1 is significantly elevated in liver cancer, pancreatic cancer, and cholangiocarcinoma tissues. Functionally, HAT1 succinyltransferase activity and the succinylation of PGAM1 by HAT1 play critical roles in promoting tumor progression in vitro and in vivo. Thus, we conclude that HAT1 is a succinyltransferase for histones and non-histones in tumorigenesis.

Aspirin modulates succinylation of PGAM1K99 to restrict the glycolysis through NF-κB/HAT1/PGAM1 signaling in liver cancer.

Aspirin as a chemopreventive agent is able to restrict the tumor growth. Phosphoglycerate mutase 1 (PGAM1) is a key enzyme of glycolysis, playing an important role in the development of cancer. However, the underlying mechanism by which aspirin inhibits the proliferation of cancer cells is poorly understood. This study aims to identify the effects of aspirin on modulating PGAM1 enzymatic activities in liver cancer. Here, we found that aspirin attenuated the PGAM1 succinylation to suppress the PGAM1 enzymatic activities and glycolysis in hepatoma cells. Mechanically, aspirin remarkably reduced the global succinylation levels of hepatoma cells, including the PGAM1 succinylation, which led to the block of conversion from 3-phosphoglycerate (3-PG) to 2-phosphoglycerate (2-PG) in cells. Interestingly, RNA-seq analysis identified that aspirin could significantly decrease the levels of histone acetyltransferase 1 (HAT1), a writer of PGAM1 succinylation, in liver cancer. As a target of aspirin, NF-κB p65 could effectively up-regulate the expression of HAT1 in the system, resulting in the increase of PGAM1 enzymatic activities. Moreover, we observed that the PGAM1-K99R mutant failed to rescue the aspirin-induced inhibition of PGAM1 activities, glycolysis, and proliferation of hepatoma cells relative to PGAM1-WT. Functionally, aspirin down-regulated HAT1 and decreased the PGAM1 succinylation levels in the tumor tissues from mice treated with aspirin in vivo. Thus, we conclude that aspirin modulates PGAM1K99 succinylation to restrict the PGAM1 activities and glycolysis through NF-κB p65/HAT1/PGAM1 signaling in liver cancer. Our finding provides new insights into the mechanism by which aspirin inhibits glycolysis in hepatocellular carcinoma.

microRNA-486-5p is implicated in the cisplatin-induced apoptosis and acute inflammation response of renal tubular epithelial cells by targeting HAT1.

The proinflammatory property of cisplatin is potentially destructive and contributes to the pathogenesis of acute kidney injury (AKI). The role and upstream regulatory mechanism of histone acetyltransferase 1 (HAT1) in acute kidney inflammation are still unknown. We performed RNA sequencing to filter differentially expressed microRNAs (miRNAs) in the kidney tissue of mice with AKI induced by cisplatin and ischemia-reperfusion. Here, we found that miR-486-5p was upregulated and that the expression of HAT1 was reduced in AKI mouse models and injured human renal proximal tubular epithelial cell (HK-2) model induced by cisplatin. miR-486-5p is implicated in cisplatin-induced kidney damage in vivo. Bioinformatics analysis predicted a potential binding site between miR-486-5p and HAT1. The Luciferase reporter assay and Western blot confirmed that miR-486-5p directly targeted the 3'-untranslated region of HAT1 mRNA and inhibited its expression in the cytoplasm of HK-2 cells. In the in vitro study, inhibiting miR-486-5p reduced apoptosis, and the expression of proinflammatory mediators was induced by cisplatin in HK-2 cells. Simultaneously, the downregulation of miR-486-5p inhibited the activation of the toll-like receptor 4 (TLR4) and nuclear factor-kappa B (NF-κB). We further found that HAT1 could inhibit apoptosis and the activation of cisplatin on the TLR4/NF-κB pathway and that the upregulation of miR-486-5p reversed this effect. Therefore, the upregulation of miR-486-5p targeting HAT1 promoted the cisplatin-induced apoptosis and acute inflammation response of renal tubular epithelial cells by activating the TLR4/NF-κB pathway, providing a new basis to highlight the potential intervention of regulating the miR-486-5p/HAT1 axis.

Hat2p recognizes the histone H3 tail to specify the acetylation of the newly synthesized H3/H4 heterodimer by the Hat1p/Hat2p complex.

Post-translational modifications of histones are significant regulators of replication, transcription, and DNA repair. Particularly, newly synthesized histone H4 in H3/H4 heterodimers becomes acetylated on N-terminal lysine residues prior to its incorporation into chromatin. Previous studies have established that the histone acetyltransferase (HAT) complex Hat1p/Hat2p medicates this modification. However, the mechanism of how Hat1p/Hat2p recognizes and facilitates the enzymatic activities on the newly assembled H3/H4 heterodimer remains unknown. Furthermore, Hat2p is a WD40 repeat protein, which is found in many histone modifier complexes. However, how the WD40 repeat proteins facilitate enzymatic activities of histone modification enzymes is unclear. In this study, we first solved the high-resolution crystal structure of a Hat1p/Hat2p/CoA/H4 peptide complex and found that the H4 tail interacts with both Hat1p and Hat2p, by which substrate recruitment is facilitated. We further discovered that H3 N-terminal peptides can bind to the Hat2p WD40 domain and solved the structure of the Hat1p/Hat2p/CoA/H4/H3 peptide complex. Moreover, the interaction with Hat2p requires unmodified Arg2/Lys4 and Lys9 on the H3 tail, suggesting a novel model to specify the activity of Hat1p/Hat2p toward newly synthesized H3/H4 heterodimers. Together, our study demonstrated the substrate recognition mechanism by the Hat1p/Hat2p complex, which is critical for DNA replication and other chromatin remodeling processes.

Histone acetyltransferase 1 is required for DNA replication fork function and stability.

The replisome is a protein complex on the DNA replication fork and functions in a dynamic environment at the intersection of parental and nascent chromatin. Parental nucleosomes are disrupted in front of the replication fork. The daughter DNA duplexes are packaged with an equal amount of parental and newly synthesized histones in the wake of the replication fork through the activity of the replication-coupled chromatin assembly pathway. Histone acetyltransferase 1 (HAT1) is responsible for the cytosolic diacetylation of newly synthesized histone H4 on lysines 5 and 12, which accompanies replication-coupled chromatin assembly. Here, using proximity ligation assay-based chromatin assembly assays and DNA fiber analysis, we analyzed the role of murine HAT1 in replication-coupled chromatin assembly. We demonstrate that HAT1 physically associates with chromatin near DNA replication sites. We found that the association of HAT1 with newly replicated DNA is transient, but can be stabilized by replication fork stalling. The association of HAT1 with nascent chromatin may be functionally relevant, as HAT1 loss decreased replication fork progression and increased replication fork stalling. Moreover, in the absence of HAT1, stalled replication forks were unstable, and newly synthesized DNA became susceptible to MRE11-dependent degradation. These results suggest that HAT1 links replication fork function to the proper processing and assembly of newly synthesized histones.

Polyamines regulate gene expression by stimulating translation of histone acetyltransferase mRNAs.

Polyamines regulate gene expression in Escherichia coli by translationally stimulating mRNAs encoding global transcription factors. In this study, we focused on histone acetylation, one of the mechanisms of epigenetic regulation of gene expression, to attempt to clarify the role of polyamines in the regulation of gene expression in eukaryotes. We found that activities of histone acetyltransferases in both the nucleus and cytoplasm decreased significantly in polyamine-reduced mouse mammary carcinoma FM3A cells. Although protein levels of histones H3 and H4 did not change in control and polyamine-reduced cells, acetylation of histones H3 and H4 was greatly decreased in the polyamine-reduced cells. Next, we used control and polyamine-reduced cells to identify histone acetyltransferases whose synthesis is stimulated by polyamines. We found that polyamines stimulate the translation of histone acetyltransferases GCN5 and HAT1. Accordingly, GCN5- and HAT1-catalyzed acetylation of specific lysine residues on histones H3 and H4 was stimulated by polyamines. Consistent with these findings, transcription of genes required for cell proliferation was enhanced by polyamines. These results indicate that polyamines regulate gene expression by enhancing the expression of the histone acetyltransferases GCN5 and HAT1 at the level of translation. Mechanistically, polyamines enhanced the interaction of microRNA-7648-5p (miR-7648-5p) with the 5'-UTR of GCN5 mRNA, resulting in stimulation of translation due to the destabilization of the double-stranded RNA (dsRNA) between the 5'-UTR and the ORF of GCN5 mRNA. Because HAT1 mRNA has a short 5'-UTR, polyamines may enhance initiation complex formation directly on this mRNA.

A HAT1-DELLA signaling module regulates trichome initiation and leaf growth by achieving gibberellin homeostasis.

Trichome initiation and leaf growth are two critical developmental processes in the plant life cycle, which need to be optimized in accordance with developmental stage and immediate surroundings. To a large extent, this optimization is achieved by fine-tuning of hormonal pathways, including the gibberellin (GA) pathway. However, the mechanism by which plants control GA homeostasis to optimize these two developmental processes is unknown. Here, we report that HAT1, a HD-ZIP II transcription factor, negatively regulates GA-mediated trichome initiation and cotyledon expansion. Both protein and transcript levels indicated that HAT1 was induced by GA, while an increased abundance of HAT1, in turn, was found to suppress GA biosynthesis and signaling, thus forming a regulatory negative feedback loop that controls GA homeostasis to fine-tune trichome development and cotyledon expansion. We also found that HAT1 interacts with DELLAs, including GAI and RGA. GAI inhibits both protein stability and the binding activity of HAT1 to its target genes. Overexpression of HAT1 in della5 can completely suppress the enhanced trichome initiation and enlarged cotyledon of della5. Our findings demonstrate that HAT1 functions as a critical repressor to regulate GA-mediated trichome initiation and cotyledon growth; in addition, we describe a novel mechanism by which the plant regulates trichome initiation and cotyledon expansion through a HAT1-DELLA regulatory module under various GA concentrations.

Hat1-Dependent Lysine Acetylation Targets Diverse Cellular Functions.

Lysine acetylation has emerged as one of the most important post-translational modifications, regulating different biological processes. However, its regulation by lysine acetyltransferases is still unclear in most cases. Hat1 is a lysine acetyltransferase originally identified based on its ability to acetylate histones. Using an unbiased proteomics approach, we have determined how loss of Hat1 affects the mammalian acetylome. Hat1+/+ and Hat1-/- mouse embryonic fibroblast cell lines were grown in both glucose- and galactose-containing media, as Hat1 is required for growth on galactose, and Hat1-/- cells exhibit defects in mitochondrial function. Following trypsin digestion of whole cell extracts, acetylated peptides were enriched by acetyllysine affinity purification, and acetylated peptides were identified and analyzed by label-free quantitation. Comparison of the acetylome from Hat1+/+ cells grown on galactose and glucose demonstrated that there are large carbon source-dependent changes in the mammalian acetylome where the acetylation of enzymes involved in glycolysis were the most affected. Comparisons of the acetylomes from Hat1+/+ and Hat1-/- cells identified 65 proteins whose acetylation decreased by at least 2.5-fold in cells lacking Hat1. In Hat1-/- cells, acetylation of the autoregulatory loop of CBP (CREB-binding protein) was the most highly affected, decreasing by up to 20-fold. In addition to the proteins involved in chromatin structure, Hat1-dependent acetylation was also found in a number of transcriptional regulators, including p53 and mitochondrial proteins. Hat1 mitochondrial localization suggests that it may be directly involved in the acetylation of mitochondrial proteins. Data are available via ProteomeXchange with identifier PXD017362.

MicroRNA-377 exerts a potent suppressive role in osteosarcoma through the involvement of the histone acetyltransferase 1-mediated Wnt axis.

It has been demonstrated that microRNAs (miRNAs) may contribute to tumorigenesis and tumor growth in osteosarcoma (OS), which is a primary malignant tumor of bone frequently diagnosed in adolescents and young people. The purpose of our investigation was to evaluate the functional relevance of miR-377 in OS and to investigate whether the mechanism was related to the histone acetyltransferase 1 (HAT1)-mediated Wnt signaling pathway. By screening differentially expressed genes in microarray GSE47572, HAT1 was found to be a candidate gene of interest. Besides, the regulatory miRNA (miR-377) of HAT1 was also selected. The interaction among miR-377, HAT1, and the Wnt signaling pathway was evaluated. In addition, the miR-377 expression was altered in OS cells (U-2OS and SOSP-9607) to assess the in vitro cell apoptosis and the in vivo tumor growth. OS tissues presented elevated HAT1 expression and decreased miR-377 expression. A putative miR-377 binding site in HAT1 3'-UTR HAT1 was verified. Cells with miR-377 overexpression or HAT1 silencing were observed to exhibit reduced HAT1 expression and promoted apoptosis, accompanied by blockade of Wnt signaling. Moreover, the in vivo experiment revealed that miR-377 overexpression or HAT1 silencing inhibited tumor growth and reduced tumor size in nude mice. Taken together, our results conclude that miR-377 may promote OS cell apoptosis through inactivation of the HAT1-mediated Wnt signaling pathway, highlighting the potential therapeutic effect of miR-377 on OS treatment.

Histone acetyltransferase 1 up regulates Bcl2L12 expression in nasopharyngeal cancer cells.

The deregulation of Bcl2L12 expression in cancer has been recognized, but the causative factors are unknown. Histone acetyltransferases (HAT) play critical roles in the regulation gene transcription. This study tests a hypothesis that the aberrant activities of HAT induce deregulation of Bcl2L12 in nasopharyngeal cancer (NPC). In this study, human NPC tissues were collected from the clinic. The expression of Bcl2L12 and HATs in NPC cells was analyzed by real time RT-PCR and Western blotting. NPC cell apoptosis was analyzed by flow cytometry. The results showed that by screening the subtypes of HAT, the levels of HAT1 were uniquely higher in NPC as compared with non-cancer nasopharyngeal tissue. The levels of Bcl2L12 in NPC cells were positively correlated with HAT1. HAT1 involved in the STAT5 binding to the Bcl2L12 promoter. HAT1 increased the expression of Bcl2L12. Bcl2L12 mediated the effects of HAT1 on suppressing NPC cell apoptosis. Absorption of the HAT1 shRNA plasmid-carrying liposomes induced NPC cell apoptosis. In conclusion, inhibition of HAT1 can induce NPC cell apoptosis via increasing Bcl2L12 expression, which can be a potential therapy for NPC treatment.

A role for CENP-A/Cse4 phosphorylation on serine 33 in deposition at the centromere.

Centromeres are the sites of assembly of the kinetochore, which connect the chromatids to the microtubules for sister chromatid segregation during cell division. Centromeres are characterized by the presence of the histone H3 variant CENP-A (termed Cse4 in Saccharomyces cerevisiae). Here, we investigated the function of serine 33 phosphorylation of Cse4 (Cse4-S33ph) in S. cerevisiae, which lies within the essential N-terminal domain (END) of the extended Cse4 N-terminus. Significantly, we identified histone H4-K5, 8, 12R to cause a temperature-sensitive growth defect with mutations in Cse4-S33 and sensitivity to nocodazole and hydroxyurea. Furthermore, the absence of Cse4-S33ph reduced the levels of Cse4 at centromeric sequences, suggesting that Cse4 deposition is defective in the absence of S33 phosphorylation. We furthermore identified synthetic genetic interactions with histone H2A-E57A and H2A-L66A, which both cause a reduced interaction with the histone chaperone FACT and reduced H2A/H2B levels in chromatin, again supporting the notion that a combined defect of H2A/H2B and Cse4 deposition causes centromeric defects. Altogether, our data highlight the importance of correct histone deposition in building a functional centromeric nucleosome and suggests a role for Cse4-S33ph in this process.

Role of Transcription Factor HAT1 in Modulating Arabidopsis thaliana Response to Cucumber mosaic virus.

Arabidopsis thaliana homeodomain-leucine zipper protein 1 (HAT1) belongs to the homeodomain-leucine zipper (HD-Zip) family class II that plays important roles in plant growth and development as a transcription factor. To elucidate further the role of HD-Zip II transcription factors in plant defense, the A. thaliana hat1, hat1hat3 and hat1hat2hat3 mutants and HAT1 overexpression plants (HAT1OX) were challenged with Cucumber mosaic virus (CMV). HAT1OX displayed more susceptibility, while loss-of-function mutants of HAT1 exhibited less susceptibility to CMV infection. HAT1 and its close homologs HAT2 and HAT3 function redundantly, as the triple mutant hat1hat2hat3 displayed increased virus resistance compared with the hat1 and hat1hat3 mutants. Furthermore, the induction of the antioxidant system (the activities and expression of enzymatic antioxidants) and the expression of defense-associated genes were down-regulated in HAT1OX but up-regulated in hat1hat2hat3 when compared with Col-0 after CMV infection. Further evidence showed that the involvement of HAT1 in the anti-CMV defense response might be dependent on salicylic acid (SA) but not jasmonic acid (JA). The SA level or expression of SA synthesis-related genes was decreased in HAT1OX but increased in hat1hat2hat3 compared with Col-0 after CMV infection, but there were little difference in JA level or JA synthesis-related gene expression among HAT1OX or defective plants. In addition, HAT1 expression is dependent on SA accumulation. Taken together, our study indicated that HAT1 negatively regulates plant defense responses to CMV.

Transcription factor HAT1 is phosphorylated by BIN2 kinase and mediates brassinosteroid repressed gene expression in Arabidopsis.

Plant steroid hormones, brassinosteroids (BRs), play essential roles in modulating cell elongation, vascular differentiation, senescence and stress responses. BRs signal through plasma membrane-localized receptor and other components to modulate the BES1/BZR1 (BRI1-EMS SUPPRESSOR 1/BRASSINAZOLE RESISTANT 1) family of transcription factors that modulate thousands of target genes. Arabodopsis thaliana homeodomain-leucine zipper protein 1 (HAT1), which encodes a homeodomain-leucine zipper (HD-Zip) class II transcription factor, was identified through chromatin immunoprecipitation (ChIP) experiments as a direct target gene of BES1. Loss-of-function and gain-of-function mutants of HAT1 display altered BR responses. HAT1 and its close homolog HAT3 act redundantly, as the double mutant hat1 hat3 displayed a reduced BR response that is stronger than the single mutants alone. Moreover, hat1 hat3 enhanced the phenotype of a weak allele of the BR receptor mutant bri1 and suppressed the phenotype of constitutive BR response mutant bes1-D. These results suggest that HAT1 and HAT3 function to activate BR-mediated growth. Expression levels of several BR-repressed genes are increased in hat1 hat3 and reduced in HAT1OX, suggesting that HAT1 functions to repress the expression of a subset of BR target genes. HAT1 and BES1 bind to a conserved homeodomain binding (HB) site and BR response element (BRRE) respectively, in the promoters of some BR-repressed genes. BES1 and HAT1 interact with each other and cooperate to inhibit BR-repressed gene expression. Furthermore, HAT1 can be phosphorylated and stabilized by GSK3 (GLYCOGEN SYNTHASE KINASE 3)-like kinase BIN2 (BRASSINOSTEROID-INSENSITIVE 2), a well established negative regulator of the BR pathway. Our results thus revealed a previously unknown mechanism by which BR signaling modulates BR-repressed gene expression and coordinates plant growth.