N-acetyltransferase 10 Research Articles

Identification and Characterization of Epigenetic Regulators of Breast Cancer Metastasis to the Brain

Breast cancer is the second leading cause of cancer-related deaths in the US, primarily because breast cancer cells metastasize multiple vital organs, including the brain. Brain metastases, refractory to chemotherapy, occur in approximately 15-35% of metastatic breast cancer cases. Current clinical management of brain metastases is limited to radiation therapy and surgical resection, and the median survival time for patients is very short. Therefore, a better therapeutic strategy against the disease is urgently needed. Emerging evidence suggests that metastasis's key steps are controlled by reversible epigenetic mechanisms, which could be targeted to prevent and treat the condition. Using a systematic in vivo shRNA screening approach, which targets around 100 actionable epigenetic regulators, we have identified several potential drivers and suppressors of breast cancer brain metastasis. Interestingly, one of the candidate regulators, N-acetyltransferase 10 (NAT10), plays a role in catalyzing acetylation on specific RNA and protein substrates, while its regulatory mechanisms in breast cancer remain unclear. We found that knockdown of NAT10 suppresses breast cancer cell proliferation and migration in vitro and brain metastasis in vivo. We are leveraging transcriptomic and proteomic analyses to uncover key biological pathways regulated by NAT10. Here, we have demonstrated that this screening strategy is potent and can be applied to identify critical epigenetic regulators in other cancer types or metastatic organs. Our results allowed us to uncover the metastatic organotropism of the epigenes and develop a novel therapeutic regimen against metastatic diseases.

Structural insights of human N-acetyltransferase 10 and identification of its potential novel inhibitors

N-acetyltransferase 10 (NAT10), is an acetyltransferase that regulates RNA stability and translation processes. Association of NAT10 with several diseases including cancer, makes it a promising therapeutic target. Remodelin is the only known NAT10 inhibitor, but the structural information related to its binding with NAT10 is still obscure. Here, we predicted the human NAT10 structure using homology modeling that was not available previously and used human NAT10 to identify the novel binding site(s) of Remodelin. The alignment of the modeled human NAT10 showed 24% identity and 37% positivity with crystal structure of tRNA (Met) cytidine acetyltransferase. Molecular docking showed binding of Remodelin with NAT10 in acetyl-CoA binding pocket. Additionally, we screened a library of FDA-approved drugs for the identification of novel inhibitors of NAT10 activity. Binding score showed that four drugs namely, Fosaprepitant (− 11.709), Leucal (− 10.46), Fludarabine (− 10.347) and Dantrolene (− 9.875) bind to NAT10 and have better binding capability when compared with Acetyl-CoA (− 5.691) and Remodelin (− 5.3). Acetyl-CoA, Remodelin, and others exhibit hits for hydrophobic, hydrophilic and hydrogen interactions. Interestingly, Remodelin and others interact with the amino acid residues ILE629, GLY639, GLY641, LEU719, and PHE722 in the Acetyl-CoA binding pocket of NAT10 similar to Acetyl-CoA. Our findings revealed that Fosaprepitant, Leucal, Fludarabine, and Dantrolene are promising molecules that can be tested and developed as potential inhibitors of NAT10 acetyltransferase activity.

Targeting NAT10 Induces Apoptosis Associated With Enhancing Endoplasmic Reticulum Stress in Acute Myeloid Leukemia Cells.

N-acetyltransferase 10 (NAT10) has oncogenic properties in many tumors through its role in different cellular biological processes. NAT10 is also a potential biomarker in acute myeloid leukemia (AML); however, the mechanisms underlying NAT10’s contribution to disease states and the effect of targeting NAT10 as a therapeutic target remain unclear. NAT10 was found to be highly expressed in patients with AML, and increased NAT10 expression was associated with poor outcomes. Additionally, targeting NAT10 via the shRNA knockdown and its pharmacotherapeutic inhibitor resulted in inhibition of cell proliferation, induction of cell cycle arrest in the G1 phase, and apoptosis in AML cells. Moreover, NAT10 induces cell cycle arrest by decreasing expression of CDK2, CDK4, CyclinD1, Cyclin E while simultaneously increasing the expression of p16 and p21. Targeting NAT10 induces ER stress through the increased expression of GRP78 and the cleavage of caspase 12, which are classical markers of ER stress. This triggered the Unfolded Protein Response (UPR) pathway by consequently increasing IRE1, CHOP, and PERK expression, all of which play crucial roles in the UPR pathway. Targeting NAT10 also activated the classical apoptotic pathway through the upregulation of the Bax/bak and the concurrent downregulation of Bcl-2. In summary, our data indicate that targeting NAT10 promotes ER stress, triggers the UPR pathway, and activates the Bax/Bcl-2 axis in AML cells. Our results thus indicate a novel mechanism underlying the induction of NAT10 inhibition-mediated apoptosis and reveal the potential for the therapeutic effect of a NAT10 specific inhibitor in AML.

Oncofetal Protein SALL4 Is Highly Expressed in Myelodysplastic Syndrome Alongside with NAT10 and P53

Introduction: Myelodysplastic syndrome (MDS) is a group of heterogeneous diseases characterized by cytologic dysplasia and refractory cytopenias as a result of ineffective hematopoiesis. We have reported that oncofetal protein SALL4 can be used as a prognostic biomarker in MDS disease. SALL4 is a transcription factor that is important for development and embryonic stem cell properties. While SALL4 expression is down-regulated or absent in most adult tissues, SALL4 is re-expressed in various cancers. We have previously reported that aberrant expression of SALL4 can be detected in MDS and AML patients. Studies in murine models, as well as in human samples, have demonstrated that SALL4 is essential for leukemic cell survival and that SALL4 transgenic mice develop an MDS-like phenotype prior to transformation to AML, suggesting that SALL4 can be a driver of MDS/AML pathogenesis. However, SALL4 expression status and related pathway in bone marrow (BM) cells and relationship with somatic gene mutations in MDS patients has not been explored. In this study, we evaluated the expression of SALL4 and related factors using single-cell mass cytometry (CyTOF) and NanoString technology in MDS patients alongside with target sequence for MDS-related mutations. Materials and methods: We evaluated the expression of SALL4 using single-cell mass cytometry (CyTOF) utilizing 28 antibodies including surface lineage markers and intracellular proteins, such as p53, ki67, c-myc and pAKT to identify SALL4 expressed cells and related pathway in bone marrow (BM) for 10 MDS patients. SALL4 expression was also analyzed in formalin-fixed paraffin-embedded (FFPE) 14 patient samples utilizing two SALL4 probes designed for NanoString technology alongside with target sequence for MDS-related mutations. One probe only detects expression of SALL4A, which is full length SALL4, while the other probe can detect both SALL4A as well as its splicing variant SALL4B. We examined the expression of a panel of 17 known SALL4 downstream target genes. Results: First, we assessed an expression level of SALL4 using CyTOF in 10 MDS patients as compared with normal BM samples (N=5). We observed that Lin-CD34+CD38+ progenitor cells in 8 out of the 10 MDS patients had higher SALL4 expression levels, while the progenitor cells of normal BM cells did not express SALL4. Similar results were observed in Lin-CD34+CD38- hematopoietic stem cells, CD11b+ mature myeloid cells, CD19+ B cells, CD235+ erythroid cells. Conversely only 3 MDS patient had weak SALL4 expression in CD3+ T cells. Subsequently, we investigated the correlation with p53, ki67, c-myc and pAKT. SALL4 is only correlated with p53 (P=0.005), while others were not. Next, we also assessed an expression level of SALL4A and SALL4A&B in 14 MDS patient bone marrow (BM) samples using Nanostring nCounter. We observed that 12 out of 14 MDS patients had higher SALL4 expression levels as compared with control normal BM samples (N=3). Next, we evaluated whether MDS patients expressed SALL4A, SALL4B, or both. Of the 14 MDS patients, 8 predominantly expressed SALL4A Of these 8 MDS patients, 5 harbored RNA splicing-related mutations, such as SF3B1 (N=4), U2AF1 (N=1). Only 1 out of 7 patients who predominantly expressed SALL4B demonstrated a splicing related mutation. Subsequently, we investigated the correlation between SALL4 and its known downstream targets. An expression of SALL4A is moderately correlated with CBLb (γ=0.53), CDH1 (γ=0.42) and NAT10 (γ=0.41). The expression of SALLA&B is moderately correlated with NAT10 (γ=0.47) and RUNX1 (γ=0.46). NAT10 (N-acetyltransferase 10) has been reported to promote transcription of RNA polymerase I and is a critical regulator of p53 homeostasis. It was identified to be a potential SALL4 downstream target in our early Chip-seq studies. In the isogenic K562 cell lines with SALL4 overexpression, higher levels of NAT10 were observed, suggesting that NAT10 is one of the downstream targets of SALL4. Conclusions: Our study has demonstrated for the first time that 1) SALL4 was expressed in various MDS BM cells confirmed by CyTOF 2) there are SALL4 splicing variants in MDS patients, particularly with SF3B1 mutations 3) a novel SALL4/NAT10/p53 link has been identified in these MDS patients. Future studies on mechanism(s) and biological role(s) of SALL4 splicing variants in MDS are needed. Disclosures No relevant conflicts of interest to declare.

Acetylation of Cytidine Residues Boosts HIV-1 Gene Expression by Increasing Viral RNA Stability

Epitranscriptomic RNA modifications, including methylation of adenine and cytidine residues, are now recognized as key regulators of both cellular and viral mRNA function. Moreover, acetylation of the N4 position of cytidine (ac4C) was recently reported to increase the translation and stability of cellular mRNAs. Here, we show that ac4C and N-acetyltransferase 10 (NAT10), the enzyme that adds ac4C to RNAs, have been subverted by human immunodeficiency virus 1 (HIV-1) to increase viral gene expression. HIV-1 transcripts are modified with ac4C at multiple discrete sites, and silent mutagenesis of these ac4C sites led to decreased HIV-1 gene expression. Similarly, loss of ac4C from viral transcripts due to depletion of NAT10 inhibited HIV-1 replication by reducing viral RNA stability. Interestingly, the NAT10 inhibitor remodelin could inhibit HIV-1 replication at concentrations that have no effect on cell viability, thus identifying ac4C addition as a potential target for antiviral drug development.

N-Acetyltransferase 10 Promotes Micronuclei Formation to Activate the Senescence-Associated Secretory Phenotype Machinery in Colorectal Cancer Cells

The formation of micronuclei (MN) is prevalent in human cancer cells and its role in activating the senescence-associated secretory phenotype (SASP) machinery has been identified recently. However, the role of MN in regulation of SASP signaling still needs to define in practical cancers. Here, we reported that in colorectal cancer cells the expression of NAT10 (N-acetyltransferase 10) could mediate MN formation through DNA replication and NAT10-positive MN could activate SASP by binding to cGAS. The chemical inhibition of NAT10 by Remodelin or genomic depletion could markedly reduce MN formation, SASP activation, and senescence in colorectal cancer cells. Cell stress such as oxidative or hypoxia could upregulate NAT10 and its associated MN formation senescence and expression of SASP factors. Statistical analysis of clinical specimens revealed correlations between NAT10 expression, MN formation, SASP signaling, and the clinicopathological features of colorectal cancer. Our data suggest that NAT10 increasing MN formation and SASP pathway activation, promoting colorectal cancer progression.

Acetylation of Cytidine Residues Boosts HIV-1 Gene Expression by Increasing Viral RNA Stability

Epitranscriptomic RNA modifications, including methylation of A and C residues, are now recognized as key regulators of both cellular and viral mRNA function. Moreover, acetylation of the N4 position of cytidine (ac4C) was recently reported to increase the translation and stability of cellular mRNAs. Here, we show that ac4C and N-acetyltransferase 10 (NAT10), the enzyme that adds ac4C to RNAs, have been subverted by human immunodeficiency virus 1 (HIV-1) to increase viral gene expression. HIV-1 transcripts are modified with ac4C at multiple discreet sites, and silent mutagenesis of these ac4C sites led to decreased HIV-1 gene expression. Similarly, loss of ac4C from viral transcripts due to depletion of NAT10 inhibited HIV-1 replication by reducing viral RNA stability. Interestingly, the NAT10 inhibitor Remodelin could inhibit HIV-1 replication at levels that have no effect on cell viability, thus identifying ac4C addition as a potential novel target for antiviral drug development.

Targeting NAT10 Induces Apoptosis by Enhancing Endoplasmic Reticulum Stress in Acute Myeloid Leukemia Cells

Background: N-acetyltransferase 10 (NAT10) is a nucleolar protein which considered as an oncogene in many tumors and plays an important role in different cellular biological processes. However the roles of NAT10 in acute myeloid leukemia (AML) remains obscure. Methods: The expression of NAT10 in the AML patients was detected by Quantitative real-time polymerase chain reaction (q-PCR). The effect and mechanism of NAT10 on apoptosis of AML cells was evaluated by CCK-8 assay, Flow cytometry analysis and Western blot assays. Finding: It was found that NAT10 expression was significantly up-regulated in AML patients compared with health donors. NAT10 knockdown and its pharmacotherapeutic inhibitor treatment significantly increased cell cycle arrest in G1 phase, and cell proliferation arrest in AML cells. NAT10 inhibition also enhanced PERK expression, indicating that apoptosis induced by NAT10 down-regulation may caused by endoplasmic reticulum (ER) stress in the cells. Interpretation: Our results indicated NAT10 is signicantly increased in AML patients, targeting NAT10 induces cell proliferation arrest and apoptosis by enhancing ER stress in AML. Our data also reveal the oncogenic effect of NAT10 in AML and potential therapeutic effect of NAT10 inhibitor in AML. Funding Statement: This work is supported in part by The National Natural Science Foundation of China (81770172); Jiangsu Provincial Special Program of Medical Science (BE2017747); Jiangsu Province 333 project(BRA2019103); Southeast University - China Pharmaceutical University Joint Research Project(2242019K3DZ02); Milstein Medical Asian American Partnership (MMAAP) Foundation Research Project Award in Hematology (2017); Key Medical of Jiangsu Province(ZDXKB2016020). Declaration of Interests: The authors declare that they have no competing interests. Ethics Approval Statement: The study was approved by the Ethics Committee of ZhongDa Hospital of Dongnan University.

NAT10 upregulation indicates a poor prognosis in acute myeloid leukemia

Background: N-acetyltransferase 10 (NAT10) is considered as an oncogene in many tumors. This study investigated the NAT10 expression in Chinese acute myeloid leukemia (AML) patients and evaluated the predictive significance of NAT10 with a single-center retrospective study. Methods: The Oncomine was used to analyze NAT10 expression in AML. We also collected bone marrow samples of 48 newly diagnosed AML patients and 20 benign individuals in our center. NAT10 mRNA expression levels were detected by real-time qPCR. Clinical data was obtained from inpatient medical records. Results: Two microarrays in Oncomine showed that NAT10 was upregulated in AML. Our data revealed that AML patients had higher NAT10 expression levels than the normal controls (P < 0.01). NPM1-mutant patients had higher NAT10 mRNA levels than NPM1-wt patients. NAT10 expression level was higher in nonremission group than in overall remission group (P < 0.05). High NAT10 expression indicated a poor progression-free survival and overall survival. Conclusions: The results support NAT10 as a potential prognostic and therapeutic biomarker for AML.

N-Acetyltransferase 10 Enhances Doxorubicin Resistance in Human Hepatocellular Carcinoma Cell Lines by Promoting the Epithelial-to-Mesenchymal Transition.

Background N-Acetyltransferase 10 (NAT10) has been reported to be expressed at high levels in hepatocellular carcinoma (HCC); however, its role in chemoresistance is unclear. This study is aimed at investigating whether NAT10 regulates the epithelial-mesenchymal transition (EMT) and chemoresistance in HCC. Methods HCC cell lines (Huh-7, Bel-7402, SNU387, and SNU449) were treated with remodelin, an inhibitor of NAT10, or transfected with small inhibitory RNAs (siRNAs) targeting NAT10 or Twist. The EMT was induced by hypoxia. The CCK-8 assay was used to quantify cell viability, the EdU incorporation assay to assess cell proliferation. siRNA knockdown efficiency and epithelial/mesenchymal marker expression were assessed by western blotting. Results Knockdown of NAT10 using siRNA or inhibition of NAT10 using remodelin increased the sensitivity of HCC cell lines to doxorubicin; similar effects were observed in cells transfected with the Twist siRNA. Inhibition of NAT10 using remodelin also reversed the ability of doxorubicin to induce the EMT in HCC cells. Furthermore, inhibiting NAT10 reversed the hypoxia-induced EMT. Finally, we confirmed that combining doxorubicin with remodelin delayed tumor growth and reduced tumor cell proliferation in a mouse xenograft model of HCC. Conclusions NAT10 may contribute to chemoresistance in HCC by regulating the EMT. The mechanism by which NAT10 regulates the EMT and doxorubicin sensitivity in HCC cells merits further investigation.

MiR-6716-5p promotes metastasis of colorectal cancer through downregulating NAT10 expression.

Background: Human N-acetyltransferase 10 (NAT10) plays pivotal roles in cellular biological processes, such as senescence, autophagy and cytokinesis. The expression of NAT10 is dysregulated in colorectal cancer (CRC) and is associated with the prognosis of patients. However, it remains unclear how NAT10 is regulated in CRC.Methods: The microRNA(miRNA) regulating NAT10 was predicted by bioinformatics analysis and further validated by real-time quantitative PCR(RT-qPCR),Western blot and dual luciferase reporter assays. The expression of the miRNA regulating NAT10 in CRC tissues was examined using RT-qPCR. Cell proliferation, cell apoptosis, cell migration and cell invasion assays were performed after transfection with miRNA mimic and inhibitor.Results: Here, we report that miR-6716-5p inhibits the expression of NAT10 in CRC. The NAT10 protein level was downregulated by the miR-6716-5p mimic, and was upregulated by the miR-6716-5p inhibitor in CRC cell lines. In addition, miR-6716-5p bound to the 3ʹ-untranslated region of NAT10 mRNA and decreased NAT10 mRNA levels. Significantly, the miR-6716-5p level was higher in the tumor tissues of the CRC patients with liver metastasis than that in the non-metastatic CRC patients. In addition, the miR-6716-5p level was correlated with poor overall survival of CRC patients with liver metastasis. The miR-6716-5p inhibitor inhibited CRC cell migration and invasion. Consistently, the miR-6716-5p mimic significantly promoted cell migration and invasion, and this effect is dependent on NAT10. However, miR-6716-5p had no effect on CRC cell proliferation and apoptosis. We found that miR-6716-5p negatively regulated E-cadherin protein levels. In addition, E-cadherin was upregulated by NAT10 in CRC cells, confirming that miR-6716-5p downregulated E-cadherin levels by inhibiting NAT10 expression.Conclusion: We demonstrated that miR-6716-5p acts as a crucial regulator of NAT10 to promote cell migration and invasion in CRC by inhibiting NAT10 expression. Our data suggest that miR-6716-5p/NAT10 might act as a potential therapeutic target for CRC treatment.

PF275 NAT10 UPREGULATION INDICATES A POOR PROGNOSIS IN ACUTE MYELOID LEUKEMIA

Background:Acute myeloid leukemia (AML) is a series of hematologic malignancies with high morbidity and mortality. It is characterized by impaired differentiation, excessive proliferation, and apoptosis escape. N‐acetyltransferase 10 (NAT10) is a transcriptional activator of telomerase reverse transcriptase (hTERT)[1]. It has acyltransferase domain and participates in microtubule acetylation, rRNA modification, DNA damage response, and cytokinesis[2–5]. NAT10 was upregulated in various kinds of tumors such as hepatocellular carcinoma, colorectal cancer, ovarian cancer and melanoma[6–9]. NAT10 upregulation is associated with poor prognosis. This study investigated NAT10 expression in AML patients and its correlation with clinical characteristics, chemotherapy response and prognosis.Aims:N‐acetyltransferase 10 (NAT10) is considered as an oncogene in many tumors. This study investigated the NAT10 expression in Chinese acute myeloid leukemia patients and evaluated the predictive significance of NAT10 with a single‐center retrospective study.Methods:We collected bone marrow samples of 48 newly diagnosed acute myeloid leukemia patients and 20 benign controls in our center. NAT10 mRNA expression levels were detected by Real‐time qPCR. Clinical data was obtained from inpatient medical records.Results:AML patients had higher NAT10 expression level than the normal controls (P &lt; 0.01). NPM1‐mutant patients had higher NAT10 expression level than NPM1‐wt patients. NAT10 expression level was higher in non‐remission group than that of overall remission group (P &lt; 0.05). High NAT10 expression indicated a poor progress free survival and overall survival.Summary/Conclusion:The results support NAT10 as a potential prognostic and therapeutic biomarker for acute myeloid leukemia.image

A Chemical Signature for Cytidine Acetylation in RNA.

N4-acetylcytidine (ac4C) is a highly conserved modified RNA nucleobase whose formation is catalyzed by the disease-associated N-acetyltransferase 10 (NAT10). Here we report a sensitive chemical method to localize ac4C in RNA. Specifically, we characterize the susceptibility of ac4C to borohydride-based reduction and show this reaction can cause introduction of noncognate base pairs during reverse transcription (RT). Combining borohydride-dependent misincorporation with ac4C's known base-sensitivity provides a unique chemical signature for this modified nucleobase. We show this unique reactivity can be used to quantitatively analyze cellular RNA acetylation, study adapters responsible for ac4C targeting, and probe the timing of RNA acetylation during ribosome biogenesis. Overall, our studies provide a chemical foundation for defining an expanding landscape of cytidine acetyltransferase activity and its impact on biology and disease.

Targeting of NAT10 enhances healthspan in a mouse model of human accelerated aging syndrome

Hutchinson-Gilford Progeria Syndrome (HGPS) is a rare, but devastating genetic disease characterized by segmental premature aging, with cardiovascular disease being the main cause of death. Cells from HGPS patients accumulate progerin, a permanently farnesylated, toxic form of Lamin A, disrupting the nuclear shape and chromatin organization, leading to DNA-damage accumulation and senescence. Therapeutic approaches targeting farnesylation or aiming to reduce progerin levels have provided only partial health improvements. Recently, we identified Remodelin, a small-molecule agent that leads to amelioration of HGPS cellular defects through inhibition of the enzyme N-acetyltransferase 10 (NAT10). Here, we show the preclinical data demonstrating that targeting NAT10 in vivo, either via chemical inhibition or genetic depletion, significantly enhances the healthspan in a LmnaG609G HGPS mouse model. Collectively, the data provided here highlights NAT10 as a potential therapeutic target for HGPS.

Inhibition of NAT10 Suppresses Melanogenesis and Melanoma Growth by Attenuating Microphthalmia-Associated Transcription Factor (MITF) Expression.

N-acetyltransferase 10 (NAT10) has been considered a target for the treatment of human diseases such as cancer and laminopathies; however, its functional role in the biology of melanocytes is questionable. Using a small molecule or small interfering RNA targeting NAT10, we examined the effect of NAT10 inhibition on melanogenesis and melanoma growth in human and mouse melanoma cells. Genetic silencing or chemical inhibition of NAT10 resulted in diminished melanin synthesis through the suppression of melanogenesis-stimulating genes such as those encoding dopachrome tautomerase (DCT) and tyrosinase in B16F10 melanoma cells. In addition, NAT10 inhibition significantly increased cell cycle arrest in S-phase, thereby suppressing the growth and proliferation of malignant melanoma cells in vitro and in vivo. These results demonstrate the potential role of NAT10 in melanogenesis and melanoma growth through the regulation of microphthalmia-associated transcription factor (MITF) expression and provide a promising strategy for the treatment of various skin diseases (melanoma) and pigmentation disorders (chloasma and freckles).

Human NAT10 Is an ATP-dependent RNA Acetyltransferase Responsible for N4-Acetylcytidine Formation in 18 S Ribosomal RNA (rRNA)

Human N-acetyltransferase 10 (NAT10) is known to be a lysine acetyltransferase that targets microtubules and histones and plays an important role in cell division. NAT10 is highly expressed in malignant tumors, and is also a promising target for therapies against laminopathies and premature aging. Here we report that NAT10 is an ATP-dependent RNA acetyltransferase responsible for formation of N(4)-acetylcytidine (ac(4)C) at position 1842 in the terminal helix of mammalian 18 S rRNA. RNAi-mediated knockdown of NAT10 resulted in growth retardation of human cells, and this was accompanied by high-level accumulation of the 30 S precursor of 18 S rRNA, suggesting that ac(4)C1842 formation catalyzed by NAT10 is involved in rRNA processing and ribosome biogenesis.

GSK-3β-regulated N-acetyltransferase 10 is involved in colorectal cancer invasion.

NAT10 (N-acetyltransferase 10) is a nucleolar protein, but may show subcellular redistribution in colorectal carcinoma. In this study, we evaluated membranous staining of NAT10 in colorectal carcinoma and its clinical implications, and explored the mechanism of regulation of NAT10 redistribution. The expression and subcellular redistribution of NAT10, β-catenin, E-cadherin, and GSK-3β were evaluated by immunohistochemistry in 222 cases of colorectal carcinoma. Regulation of NAT10 and its influence on cell motility were analyzed with inhibitors of GSK-3β, transfection of wild-type or kinase-inactivated GSK-3β, or expression of various domains of NAT10, and evaluated with immunofluorescence, Western blotting, and Transwell assays. NAT10 localized mainly in the nucleoli of normal tissues, and was redistributed to the membrane in cancer cells, particularly at the invasive "leading edge" of the tumor. This correlated well with nuclear accumulation of β-catenin (P<0.001; χ2=68.213). In addition, NAT10 membrane staining reflected the depth of invasion and tendency to metastasize (all P values<0.001), and was associated with a poorer prognosis (P=0.023; χ2=5.161). Evaluation of the mechanism involved demonstrated that subcellular redistribution of NAT10 may result from its increased stability and nuclear export, which is brought about by inhibition of GSK-3β. Moreover, redistribution of NAT10 induces alteration of cytoskeletal dynamics and increases cancer cell motility. The subcellular redistribution of NAT10 can be induced by decreases in GSK-3β activity. This redistribution increases cancer cell motility, and is, thus, correlated with invasive potential and poorer clinical outcome. This finding suggests that NAT10 may be a useful prognostic marker and potential therapeutic target in colorectal carcinoma.

Highlights of This Issue

Manipulation of the apoptosis pathway is an appealing strategy for cancer treatment using BH3 mimetics such as ABT-263, although predictive biomarkers are required to identify patients who may benefit from their use. To investigate this problem, Suryani and colleagues studied the in vivo efficacy of ABT-263 against 31 pediatric acute lymphoblastic leukemia xenografts. High MCL1 expression and function correlated with in vivo ABT-263 resistance, and in vitro assays predicted in vivo ABT-263 responses. These approaches could be included in the design of prospective clinical trials to determine if they can identify patients who may respond to treatment with this class of therapeutic agents.Gastric carcinoma (GC) is the second leading cause of cancer deaths in the world, with many deaths occurring in East Asia. To identify DNA methylation biomarkers for prediction of GC metastasis, scientists, and oncologists from China, the United States, Japan, and Korea have profiled differential methylation patterns in GCs and perform an in-depth characterization of methylation changes in 73 candidate genes. The authors have established a methylation biomarker-set composed of three genes GFRA1, SRF, and ZNF382 that could be used to synergistically predict GC metastasis and patients' overall survival from multiple patient cohorts in China, Japan, and Korea.TAZ, the core component of Hippo signaling pathway, attracts increasing attention as a critical player in tumorigenesis. Using an integrated translational approach, the authors explored the role of TAZ in non-small cell lung cancer (NSCLC). Noguchi and colleagues showed that higher TAZ expression was associated with shorter patient survival, and TAZ promoted lung cancer cell proliferation in vitro and tumor development in vivo. Moreover, TAZ regulated the expression of ErbB ligands and the EGFR signaling pathway was activated in NSCLC tissues with high TAZ expression. This study offers potential therapeutic strategies, either directly against TAZ or indirectly via EGFR pathway.Activation of Wnt-signaling is a common event in colorectal carcinoma (CRC), but its role in CRC metastasis is still under extensive study. In the present study, Zhang and colleagues revealed subcellular redistribution of NAT10 (N-acetyltransferase 10) in CRCs, which correlated well with nuclear translocation of β-catenin and reflected invasive potential of CRC. They demonstrated that inhibition of GSK-3β induced NAT10 redistribution through increasing its stability and nuclear export, which consequently enhanced cytoskeletal remodeling and promoted migration, invasion, and metastasis of cancer cells. These findings suggest NAT10 could be a useful prognostic marker and potential therapeutic target in CRC.

HALP, A Novel Transcriptional U Three Protein (t-UTP), Activates RNA Polymerase I Transcription by Binding and Acetylating the Upstream Binding Factor (UBF)

Transcription of ribosome RNA precursor (pre-rRNA) and pre-rRNA processing are coordinated by a subset of U three proteins (UTPs) known as transcriptional UTPs (t-UTPs), which participate in pre-rRNA transcription in addition to participation in 18 S rRNA processing. However, the mechanism by which t-UTPs function in pre-rRNA transcription remains undetermined. In the present study, we identified hALP, a histone acetyl-transferase as a novel t-UTP. We first showed that hALP is nucleolar, and is associated with U3 snoRNA and required for 18 S rRNA processing. Moreover, depletion of hALP resulted in a decreased level of 47 S pre-rRNA. Ectopic expression of hALP activated the rDNA promoter luciferase reporter and knockdown of hALP inhibited the reporter. In addition, hALP bound rDNA. Taken together these data identify hALP as a novel t-UTP. Immunoprecipitation and GST pulldown experiments showed that hALP binds the upstream binding factor (UBF) in vivo and in vitro. It is of importance that hALP acetylated UBF depending on HAT in vivo, and hALP but not hALP (ΔHAT) facilitated the nuclear translocation of the RNA polymerase I (Pol I)-associated factor 53 (PAF53) from the cytoplasm and promoted the association of UBF with PAF53. Thus, we provide a mechanism in which a novel t-UTP activates Pol I transcription by binding and acetylating UBF.

DNA damage induces N-acetyltransferase NAT10 gene expression through transcriptional activation

NAT10 (N-acetyltransferase 10) is a protein with histone acetylation activity and primarily identified to be involved in regulation of telomerase activity. The presented research shows its transcriptional activation by genotoxic agents and possible role in DNA damage. NAT10 mRNA could be markedly increased by using hydrogen peroxide (H2O2) or cisplatin in a dose- and time-dependent way, and the immunofluorescent staining revealed that the treatment of H2O2 or cisplatin induced focal accumulation of NAT10 protein in cellular nuclei. Both H2O2 and cisplatin could stimulate the transcriptional activity of the NAT10 promoter through the upstream sequences from -615 bp to +110 bp, with which some nuclear proteins interacted. Ectopic expression of NAT10 could enhance the number of survival cells in the presence of H2O2 or cisplatin. The above results suggested that NAT10 could be involved in DNA damage response and increased cellular resistance to genotoxicity.