Transcription Of Proapoptotic Genes Research Articles

Astaxanthin enhances the development of bovine cloned embryos by inhibiting apoptosis and improving DNA methylation reprogramming of pluripotency genes

Low cloning efficiency limits the wide application of somatic cell nuclear transfer technology. Apoptosis and incomplete DNA methylation reprogramming of pluripotency genes are considered as the main causes for low cloning efficiency. Astaxanthin (AST), a powerfully antioxidative and antiapoptotic carotenoid, is recently shown to improve the development of early embryos, however, the potential role of AST during the development of cloned embryos remains unclear. This study displayed that treating cloned embryos with AST significantly increased the blastocyst rate and total blastocyst cell number in a concentration dependent manner, and also alleviated the damage of H2O2 to the development of cloned embryos. In addition, compared with the control group, AST significantly reduced the apoptotic cell number and rate in cloned blastocysts, and the significantly upregulated expression of anti-apoptotic gene Bcl2l1 and antioxidative genes (Sod1 and Gpx4) and downregulated transcription of pro-apoptotic genes (Bax, P53 and Caspase3) were observed in the AST group. Moreover, AST treatment facilitated DNA demethylation of pluripotency genes (Pou5f1, Nanog and Sox2), in accompany with the improved transcription levels of DNA methylation reprogramming genes (Tet1, Tet3, Dnmt1, Dnmt3a and Dnmt3b) in cloned embryos, and then, the significantly upregulated expression levels of embryo development related genes including Pou5f1, Nanog, Sox2 and Cdx2 were observed in comparison with the control group. In conclusion, these results revealed that astaxanthin enhanced the developmental potential of bovine cloned embryos by inhibiting apoptosis and improving DNA methylation reprogramming of pluripotency genes, and provided a promising approach to improve cloning efficiency.

Retraction Note: Human papillomavirus type 77 E6 protein selectively inhibits p53-dependent transcription of proapoptotic genes following UV-B irradiation.

Retraction Note: Human papillomavirus type 77 E6 protein selectively inhibits p53-dependent transcription of proapoptotic genes following UV-B irradiation.

Low-Dose Trans-Resveratrol Ameliorates Diabetes-Induced Retinal Ganglion Cell Degeneration via TyrRS/c-Jun Pathway.

The purpose of this study was to investigate the protective effect of low-dose trans-resveratrol (trans-RSV) on diabetes-induced retinal ganglion cell (RGC) degeneration and its possible mechanism. A streptozotocin-induced diabetic mouse model was established and treated with or without trans-RSV intragastric administration (10 mg/kg body weight/day) for 12 weeks. Oscillatory potentials (Ops) of the dark-adapted electroretinogram (ERG) were recorded. The number of RGCs was detected by Tuj1 and TUNEL staining. The apoptosis markers in the retina were analyzed by Western blot. The cross sections of optic nerves were observed by transmission electron microscopy. In addition, mouse neuroblastoma N2a cells were injured by high-glucose (HG) treatment. Cell viability and apoptosis were measured with or without low-dose trans-RSV treatment. The intracellular localization of tyrosyl transfer-RNA synthetase (TyrRS) was observed in both mouse retinas and N2a cells. The effects of low-dose trans-RSV on the binding of TyrRS to the transcription factor c-Jun and the binding of c-Jun to pro-apoptotic genes were analyzed by co-IP and ChIP assays in HEK 293 cells. Trans-RSV relieved electrophysiological injury of retinas and inhibited RGC apoptosis in diabetic mice. It also protected N2a cells from HG-induced apoptosis. Additionally, it promoted TyrRS nuclear translocation in both diabetic mouse retinas and HG-treated N2a cells. Trans-RSV promoted TyrRS binding to c-Jun, inhibited the phosphorylation of Ser-63 of c-Jun, and downregulated pro-apoptotic gene transcription. Low-dose trans-RSV can ameliorate diabetes-induced RGC degeneration via the TyrRS/c-Jun pathway. It can promote TyrRS nuclear translocation and bind to c-Jun, downregulating c-Jun phosphorylation and downstream pro-apoptotic genes.

β-arrestin1-E2F1-ac axis regulates physiological apoptosis and cell cycle exit in cellular models of early postnatal cerebellum.

Development of the cerebellum is characterized by rapid proliferation of cerebellar granule cell precursors (GCPs) induced by paracrine stimulation of Sonic hedgehog (Shh) signaling from Purkinje cells, in the external granular layer (EGL). Then, granule cell precursors differentiate and migrate into the inner granular layer (IGL) of the cerebellum to form a terminally differentiated cell compartment. Aberrant activation of Sonic hedgehog signaling leads to granule cell precursors hyperproliferation and the onset of Sonic hedgehog medulloblastoma (MB), the most common embryonal brain tumor. β-arrestin1 (ARRB1) protein plays an important role downstream of Smoothened, a component of the Sonic hedgehog pathway. In the medulloblastoma context, β-arrestin1 is involved in a regulatory axis in association with the acetyltransferase P300, leading to the acetylated form of the transcription factor E2F1 (E2F1-ac) and redirecting its activity toward pro-apoptotic gene targets. This axis in the granule cell precursors physiological context has not been investigated yet. In this study, we demonstrate that β-arrestin1 has antiproliferative and pro-apoptotic functions in cerebellar development. β-arrestin1 silencing increases proliferation of Sonic hedgehog treated-cerebellar precursor cells while decreases the transcription of E2F1-ac pro-apoptotic targets genes, thus impairing apoptosis. Indeed, chromatin immunoprecipitation experiments show a direct interaction between β-arrestin1 and the promoter regions of the pro-apoptotic E2F1 target gene and P27, indicating the double role of β-arrestin1 in controlling apoptosis and cell cycle exit in a physiological context. Our data elucidate the role of β-arrestin1 in the early postnatal stages of cerebellar development, in those cell compartments that give rise to medulloblastoma. This series of experiments suggests that the physiological function of β-arrestin1 in neuronal progenitors is to directly control, cooperating with E2F1 acetylated form, transcription of pro-apoptotic genes.

Investigation of Potential In Vitro Anticancer and Antimicrobial Activities of Balanites aegyptiaca (L.) Delile Fruit Extract and Its Phytochemical Components.

The therapeutic importance of Balanites aegyptiaca in folk medicine for the treatment of several common human diseases has led researchers to conduct phytochemical and pharmacological studies on extracts from various parts of the plant. In the current study, the phytochemical composition of the B. aegyptiaca methanolic fruit extract was characterized, and its antimicrobial activity was evaluated together with the cytotoxic activity against MCF-7, PC-3, and Caco-2, compared with normal Vero cells. Further, its effects on cell cycle arrest, apoptosis induction and expression of apoptosis-related genes were assessed. The phytochemical screening revealed the presence of fatty acids and their esters in addition to phytosterols, steroid derivatives, and bioflavonoid glycosides with oleic and palmitic acids being the prevalent components (24.12 and 21.56%, respectively). The results showed considerable cytotoxic activity of the extract against the three cancer cell lines (MCF-7, PC-3, and Caco-2) with a selectivity index ranging from 5.07 to 6.52. This effect was further confirmed with the accompanied increased total apoptosis of treated PC-3 cells (19.22% of the total number of cells) compared to the control cells (0.64% of the total number of cells) with cell cycle arrest at G1 phase and the increased transcription of pro-apoptotic genes including P53 (3.69) and BAX (3.33) expressed as fold change (2^ ΔΔCT). The calculated minimum inhibitory concentration (MIC) was similar (62.5 µg/mL) against the three tested bacterial strains (Acinetobacter johnsonii, Serratia marcescens and Agrobacterium tumefaciens), while it was higher than 1000 µg/mL for the fungal species (Rhizoctonia solani, Penicillium italicum, and Fusarium oxysporium). Our findings suggest a promising anticancer activity for B. aegyptiaca, which paves the way for more detailed future studies.

Quantitative Phosphoproteomics and Acetylomics of Safranal Anticancer Effects in Triple-Negative Breast Cancer Cells.

Safranal, as an aroma in saffron, is one of the cytotoxic compounds in saffron that causes cell death in triple-negative breast cancer cells. Our recent research reported the anti-cancer effects of safranal, which further demonstrated its impact on protein translation, mitochondrial dysfunction, and DNA fragmentation. To better understand the underlying mechanisms, we identified acetylated and phosphorylated peptides in safranal-treated cancer cells. We conducted a comprehensive phosphoproteomics and acetylomics analysis of safranal-treated MDA-MB-231 cells by using a combination of TMT labeling and enrichment methods including titanium dioxide and immunoprecipitation. We provide a wide range of phosphoproteome regulation in different signaling pathways that are disrupted by safranal treatment. Safranal influences the phosphorylation level on proteins involved in DNA replication and repair, translation, and EGFR activation/accumulation, which can lead the cells into apoptosis. Safranal causes DNA damage which is followed by the activation of cell cycle checkpoints for DNA repair. Over time, checkpoints and DNA repair are inhibited and cells are under a mitotic catastrophe. Moreover, safranal prevents repair by the hypo-acetylation of H4 and facilitates the transcription of proapoptotic genes by hyper-acetylation of H3, which push the cells to the brink of death.

Chromatin remodeler Dmp18 regulates apoptosis by controlling H2Av incorporation in Drosophila imaginal disc development.

Programmed Cell Death (PCD) or apoptosis is a highly conserved biological process and plays essential roles both in the development and stress context. In Drosophila, expression of pro-apoptotic genes, including reaper (rpr), head involution defective (hid), grim, and sickle (skl), is sufficient to induce cell death. Here, we demonstrate that the chromatin remodeler Dmp18, the homolog of mammalian Znhit1, plays a crucial role in regulating apoptosis in eye and wing development. We showed that loss of Dmp18 disrupted eye and wing development, up-regulated transcription of pro-apoptotic genes, and induced apoptosis. Inhibition of apoptosis suppressed the eye defects caused by Dmp18 deletion. Furthermore, loss of Dmp18 disrupted H2Av incorporation into chromatin, promoted H3K4me3, but reduced H3K27me3 modifications on the TSS regions of pro-apoptotic genes. These results indicate that Dmp18 negatively regulates apoptosis by mediating H2Av incorporation and histone H3 modifications at pro-apoptotic gene loci for transcriptional regulation. Our study uncovers the role of Dmp18 in regulating apoptosis in Drosophila eye and wing development and provides insights into chromatin remodeling regulating apoptosis at the epigenetic levels.

Altering mammalian transcription networking with ADAADi: An inhibitor of ATP-dependent chromatin remodeling

Active DNA-dependent ATPase A Domain inhibitor (ADAADi) is the only known inhibitor of ATP-dependent chromatin remodeling proteins that targets the ATPase domain of these proteins. The molecule is synthesized by aminoglycoside phosphotransferase enzyme in the presence of aminoglycosides. ADAADi interacts with ATP-dependent chromatin remodeling proteins through motif Ia present in the conserved helicase domain, and thus, can potentially inhibit all members of this family of proteins. We show that mammalian cells are sensitive to ADAADi but with variable responses in different cell lines. ADAADi can be generated from a wide variety of aminoglycosides; however, cells showed differential response to ADAADi generated from various aminoglycosides. Using HeLa and DU145 cells as model system we have explored the effect of ADAADi on cellular functions. We show that the transcriptional network of a cell type is altered when treated with sub-lethal concentration of ADAADi. Although ADAADi has no known effects on DNA chemical and structural integrity, expression of DNA-damage response genes was altered. The transcripts encoding for the pro-apoptotic proteins were found to be upregulated while the anti-apoptotic genes were found to be downregulated. This was accompanied by increased apoptosis leading us to hypothesize that the ADAADi treatment promotes apoptotic-type of cell death by upregulating the transcription of pro-apoptotic genes. ADAADi also inhibited migration of cells as well as their colony forming ability leading us to conclude that the compound has effective anti-tumor properties.

Cooperative treatment effectiveness of ATR and HSP90 inhibition in Ewing\u2019s sarcoma cells

IntroductionEwing's sarcoma is an aggressive childhood malignancy whose outcome has not substantially improved over the last two decades. In this study, combination treatments of the HSP90 inhibitor AUY922 with either the ATR inhibitor VE821 or the ATM inhibitor KU55933 were investigated for their effectiveness in Ewing's sarcoma cells.MethodsEffects were determined in p53 wild-type and p53 null Ewing's sarcoma cell lines by flow cytometric analyses of cell death, mitochondrial depolarization and cell-cycle distribution as well as fluorescence and transmission electron microscopy. They were molecularly characterized by gene and protein expression profiling, and by quantitative whole proteome analysis.ResultsAUY922 alone induced DNA damage, apoptosis and ER stress, while reducing the abundance of DNA repair proteins. The combination of AUY922 with VE821 led to strong apoptosis induction independent of the cellular p53 status, yet based on different molecular mechanisms. p53 wild-type cells activated pro-apoptotic gene transcription and underwent mitochondria-mediated apoptosis, while p53 null cells accumulated higher levels of DNA damage, ER stress and autophagy, eventually leading to apoptosis. Impaired PI3K/AKT/mTOR signaling further contributed to the antineoplastic combination effects of AUY922 and VE821. In contrast, the combination of AUY922 with KU55933 did not produce a cooperative effect.ConclusionOur study reveals that HSP90 and ATR inhibitor combination treatment may be an effective therapeutic approach for Ewing's sarcoma irrespective of the p53 status.

PRAS40 Phosphorylation Correlates with Insulin-Like Growth Factor-1 Receptor-Induced Resistance to Epidermal Growth Factor Receptor Inhibition in Head and Neck Cancer Cells.

EGFR inhibitors have shown poor efficacy in head and neck squamous cell carcinoma (HNSCC) with demonstrated involvement of the insulin-like growth factor-1 receptor (IGF1R) in resistance to EGFR inhibition. IGF1R activates the PI3K-Akt pathway, which phosphorylates proline-rich Akt substrate of 40 kDa (PRAS40) to cease mTOR inhibition resulting in increased mTOR signaling. Proliferation assays separated six HNSCC cell lines into two groups: sensitive to EGFR inhibition or resistant; all sensitive cell lines demonstrated reduced sensitivity to EGFR inhibition upon IGF1R activation. Reverse phase protein microarray analysis and immunoblot identified a correlation between increased PRAS40 phosphorylation and IGFR-mediated resistance to EGFR inhibition. In sensitive cell lines, PRAS40 phosphorylation decreased 44%-80% with EGFR inhibition and was restored to 98%-196% of control by IGF1R activation, while phosphorylation was unaffected in resistant cell lines. Possible involvement of mTOR in this resistance mechanism was demonstrated through a similar pattern of p70S6K phosphorylation. However, addition of temsirolimus, an mTORC1 inhibitor, was insufficient to overcome IGF1R-mediated resistance and suggested an alternative mechanism. Forkhead box O3a (FOXO3a), which has been reported to complex with PRAS40 in the cytoplasm, demonstrated a 6-fold increase in nuclear to cytoplasmic ratio upon EGFR inhibition that was eliminated with concurrent IGF1R activation. Transcription of FOXO3a-regulated TRAIL and PTEN-induced putative kinase-1 (PINK1) was increased with EGFR inhibition in sensitive cell lines; this effect was diminished with IGF1R stimulation. IMPLICATIONS: These data suggest PRAS40 may play an important role in IGF1R-based therapeutic resistance to EGFR inhibition, and this likely occurs via inhibition of FOXO3a-mediated proapoptotic gene transcription.

AATF/Che-1-An RNA Binding Protein at the Nexus of DNA Damage Response and Ribosome Biogenesis.

The DNA damage response (DDR) is a complex signaling network that is activated upon genotoxic stress. It determines cellular fate by either activating cell cycle arrest or initiating apoptosis and thereby ensures genomic stability. The Apoptosis Antagonizing Transcription Factor (AATF/Che-1), an RNA polymerase II-interacting transcription factor and known downstream target of major DDR kinases, affects DDR signaling by inhibiting p53-mediated transcription of pro-apoptotic genes and promoting cell cycle arrest through various pathways instead. Specifically, AATF was shown to inhibit p53 expression at the transcriptional level and repress its pro-apoptotic activity by direct binding to p53 protein and transactivation of anti-apoptotic genes. Solid and hematological tumors of various organs exploit this function by overexpressing AATF. Both copy number gains and high expression levels of AATF were associated with worse prognosis or relapse of malignant tumors. Recently, a number of studies have enabled insights into the molecular mechanisms by which AATF affects both DDR and proliferation. AATF was found to directly localize to sites of DNA damage upon laser ablation and interact with DNA repair proteins. In addition, depletion of AATF resulted in increased DNA damage and decrease of both proliferative activity and genotoxic tolerance. Interestingly, considering the role of ribosomal stress in the regulation of p53, more recent work established AATF as ribosomal RNA binding protein and enabled insights into its role as an important factor for rRNA processing and ribosome biogenesis. This Mini Review summarizes recent findings on AATF and its important role in the DDR, malignancy, and ribosome biogenesis.

ROS-mediated JNK pathway critically contributes to PFOS-triggered apoptosis in SH-SY5Y cells

Recent studies have indicated that perfluorooctane sulfonate (PFOS) and its derivatives can lead to neurotoxicity. In the present study, we showed that PFOS may trigger neuronal apoptosis through a c-Jun N-terminal kinase (JNK)-related mechanism. We revealed that c-Jun N-terminal kinase (JNK) was robustly activated in PFOS-exposed neuronal cells. The doses of PFOS that initiates JNK activation coincides with that inducing neuronal apoptosis, as confirmed by western blot and Annexin V-PE/7-AAD analyses. In addition, we found that reactive oxidative species (ROS) accumulation plays a casual role in PFOS-initiated JNK activation, as treatment with ROS scavenger N-acetyl-l-cysteine (NAC) abrogated PFOS-induced mitochondrial and nuclear translocation of phosphorylated JNK (p-JNK). In keeping with this notion, the expression of JNK downstream pro-apoptotic target Bim was increased following PFOS exposure in JNK- and ROS-dependent manners. Finally, Annexin V-PE/7-AAD analysis uncovered that treatment with NAC or SP600125 could significantly impair PFOS-induced neuronal apoptosis. These findings implicate that JNK signaling is critically involved in PFOS-induced neuronal death by virtue of mitochondrial translocation and the transcription of pro-apoptotic genes.

AZD3759 induces apoptosis in hepatoma cells by activating a p53-SMAD4 positive feedback loop

AZD3759 is a tyrosine kinase inhibitor and has an encouraging future in treating brain metastases of non-small cell lung cancer. Here, we determined that AZD3759 suppressed the viability of HepG2 cells, a hepatoma cell line, and induced their apoptosis, suggesting a new therapeutic potential of AZD3759 in hepatocellular carcinoma (HCC) treatment. Furthermore, we found that the activation of p53-SMAD family member 4 (SMAD4) positive feedback loop was involved in the induction of bulks of apoptosis in HepG2 cells in response to AZD3759 treatment. In this positive feedback loop, p53 induced the expression of SMAD4 by directly promoting its transcription as shown by p53 could bind to SMAD4 promoter; SMAD4, in turn, promoted the nuclear translocation of p53, which increased the transcription of pro-apoptotic genes, including PUMA and BAX (two p53 target genes) and finally resulted in apoptosis. To the best of our knowledge, p53-induced SMAD4 transcription and SMAD4-determined the sub-location of p53 have not been reported. Taken together, our results demonstrated that AZD3759 might be an alternative strategy for HCC treatment and activating p53-SMAD4 positive feedback loop might enhance its therapeutic effects on HCC.

Haploinsufficiency for NR3C1 Drives Glucocorticoid Resistance By Inactivation the PI3K/AKT/GSK3β/Bim Pathway in Adult Acute Lymphoblastic Leukemia

Introduction: Although steady improvements to chemotherapeutic treatments have helped cure 80% of childhood B-cell acute lymphoblastic leukemia (B-ALL) cases, chemotherapy has proven to be less effective in treating the majority of adult patients, the equivalent rate for adults remains poor at 30-40%, with relapse representing the leading cause of mortality in both children and adults. Development of chemo-resistance is a crucial factor contributing to relapse, therefore understanding the biological mechanisms underlying this resistance is imperative for discovering innovative treatment strategies. Relapse specific/enriched genetic alterations in the emergence of clones that have gained a selective advantage under the pressure of specific chemotherapeutics. We previously performed longitudinal whole-exome sequencing analysis in diagnosis/relapse pairs from adult patients with B-ALL revealed relapse-specific mutations in NR3C1 gene, encoding the glucocorticoid receptor (GCR), are frequently detected. Furthermore, the mutations of NR3C1 identified in relapsed B-ALL patients all resulted in haploinsufficiency for NR3C1. In this study, we sought to delineate whether reduced expression of NR3C1 could give rise to chemo-resistance in B-ALL and elucidate the mechanism responsible for the resistance.Methods: We performed clinical sample and ex vivo cell studies to elucidate the relationship between endogenous expression of NR3C1 in ALL cells and the sensitivity to dexamethasone. We further induced enforced expression of NR3C1 in dexamethasone-resistant ALL cells by being transfected with the expression vector of NR3C1. Moreover, we used CRISRP/CAS9 system to knock out NR3C1 gene in dexamethasone- susceptible ALL cell lines. Finally, we performed whole-genome transcriptome sequencing (RNA-seq) and Western-blotting analysis to elucidate the molecular mechanisms.Results: (1) We examined the correlation of endogenous expression of NR3C1 with the sensitivity to dexamethasone in five human ALL cell lines, Reh, Jurkat, CCRF-CEM, Nalm6 and 6T-CEM. Our data suggested that the susceptibility of ALL cells to dexamethasone was positively correlated with endogenous NR3C1 mRNA and protein level. (2) Enforced expression of NR3C1 in dexamethasone-resistant ALL cells can reverse the resistance; (3) Knockout of NR3C1 gene in dexamethasone- susceptible ALL cells can confer resistance to glucocorticoid. (4) RNA-seq analysis showed that NR3C1 protein involved in the regulation of cell apoptosis, p53 pathway and cell cycle. NR3C1 protein regulated transcription of PI3K-related genes in ALL cells, which diminished PIK3CD transcription and increased mRNA level of PIK3R6, PIK3R5, PIK3R2, AKT3 and GSK3β. In addition, NR3C1 increased transcription of pro-apoptotic genes, BCL2L11 (encoding Bim protein), BMF and BOK, and diminished transcription of anti-apoptotic genes, BCL2 and BAG2. Further Western-blotting confirmed that overexpression of NR3C1 increased protein level of p-AKT (Ser 473), p-GSK3β (Ser 9), Bim and Bad, and diminished protein level of of Bcl-2 and Bcl-xl.Conclusions: Our results provide, for the first time, evidence that haploinsufficiency for NR3C1 in ALL cells causes resistance specifically to glucocorticoid, which are the backbone of induction therapy, by disrupting the activation of PI3K/AKT/GSK3 signaling pathway and the balance between pre-apoptotic proteins and anti-apoptotic proteins. DisclosuresNo relevant conflicts of interest to declare.

4-1BB-Costimulated CAR-Mediated Non-Canonical NF-Kb Signaling Enhances CAR T Cell Survival and Suppresses Bim Expression

Chimeric Antigen Receptor (CAR) T cell therapy induces deep and durable responses in a large percentage of patients with B-cell malignancies. These responses often correlate with CAR T cell persistence in patients. The first two FDA-approved CAR-T cell therapies employ 2nd generation CARs that use different costimulatory domains derived from either CD28 or 4-1BB. Data from pre-clinical studies as well as clinical trials suggest that 4-1BB CAR (BBz) T cells persist longer than CD28 CAR (28z) T cells.One signal associated with cellular survival and activated by endogenous 4-1BB, but not CD28, is the non-canonical NF-kB (ncNF-kB) pathway. NcNF-kB is required for memory T cell persistence and enhances tumor cell survival by suppressing pro-apoptotic gene transcription. Therefore, we hypothesize that the BBz, but not the 28z CAR, activates ncNF-kB signaling, which promotes CAR T cell persistence by suppressing pro-apoptotic gene expression.Using primary human T cells isolated from the apheresis products of anonymous healthy donors, we generated 28z or BBz T cells by lentiviral transduction following activation by CD3 and CD28. Induction of ncNF-kB signaling following CAR activation was assessed by western blot. NcNF-kB function was evaluated by concomitant expression of a dominant-negative mutant of NF-kB-inducing Kinase (dnNIK) to block the ncNF-kB pathway. In addition to pathway analysis by western blotting, T cell proliferation, immunophenotype and survival were assessed by bead-based counting via flow cytometry. To explore mechanisms affecting survival, pro- and anti-apoptotic gene expression was analyzed by qPCR and western blot over three weeks following restimulation through the CAR.Following CAR activation, ncNF-kB signaling was detected in BBz but not 28z T cell lysates. Control mRFP BBz T cells expanded approximately 10 fold more than BBz T cells coexpressing dnNIK. DnNIK-expressing BBz T cells exhibited higher rates of cell death contributing to the observed differences apparent in ex vivo expansion. This cell death was associated with a 2 fold increase in the message and nearly 3 fold increase in the expression of the pro-apoptotic protein, Bim, in the dnNIK BBz T cells relative to control. In contrast, dnNIK 28z T cells had no appreciable difference in proliferation or survival compared with control.Therefore, BBz, but not 28z signaling activates the ncNF-kB pathway, which protects BBz T cells from cell death likely by restricting the expression of the pro-apoptotic protein, Bim. DisclosuresMilone:Novartis: Patents & Royalties.

Expression of the human TRIM14 and its mutant form (P207L) promotes apoptosis in transgenic loaches.

The tripartite-motif (TRIM)14 protein, one of the TRIM family members, was shown to participate in the antiviral and antibacterial defence. Besides, it appears to play an essential role in the processes of oncogenesis. In some types of human tumour cells, TRIM14 has been shown to inhibit apoptosis, while in others-the overexpression of TRIM14 promotes apoptosis. However, whether TRIM14 mediates apoptosis in the normal cells remains unknown. In the present study, we investigated the possible participation of the human TRIM14 gene and its mutant form (620C > T) in the induction of apoptosis in the transgenic larvae loach Misgurnus fossilis L. We observed that the expression of both forms of TRIM14 gene was accompanied by the increase of the frequency of pyknotic nuclei in fish embryos compared to control groups. Accordingly, using the TUNEL assay, the enhanced apoptosis was revealed upon expression of both forms of TRIM14 gene. The transcription of proapoptotic genes (bax, tp53, and casp9) was significantly increased in transgenic loaches expressing human wild-type TRIM14, but remained unchanged upon expression of its mutant form. In addition, the transcription of c-myc was upregulated in transgenic loaches expressing both forms. Thus, it can be assumed that during embryonic development TRIM14 has a proapoptotic effect on the cells via the activation of c-myc, tp53, and bax genes. Apparently, the mutant TRIM14 directs apoptosis via c-myc by p53-independent mechanism.

XAF1 forms a positive feedback loop with IRF-1 to drive apoptotic stress response and suppress tumorigenesis

X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1) is a proapoptotic tumor suppressor that is frequently inactivated in multiple human cancers. However, the molecular basis for the XAF1-mediated growth inhibition remains largely undefined. Here, we report that XAF1 forms a positive feedback loop with interferon regulatory factor-1 (IRF-1) and functions as a transcriptional coactivator of IRF-1 to suppress tumorigenesis. Under various stressful conditions, XAF1 transcription is activated by IRF-1, and elevated XAF1 stabilizes and activates IRF-1. Mechanistically, XAF1 binds to the multifunctional domain 2 of IRF-1 via the zinc finger domain 6, thereby hindering C-terminus of Hsc70-interacting protein (CHIP) interaction with and ubiquitination of IRF-1. Activation of the IRF-1−XAF1 loop greatly increases stress-induced apoptosis and decreases the invasive capability of tumor cells. Oncogenic Ras and growth factors interfere with the IRF-1−XAF1 interplay via Erk-mediated repression of XAF1 transcription. Furthermore, XAF1 enhances IRF-1-mediated transcription of proapoptotic genes via the XAF1-IRF-1 complex formation on these target promoters. Meanwhile, XAF1 inhibits NF-κB-mediated tumor cell malignancy by reinforcing IRF-1 binding to a subset of coregulated promoters. Expression levels of IRF-1 and XAF1 correlate tightly in both cancer cell lines and primary tumors, and XAF1-induced tumor regression is markedly attenuated in IRF-1-depleted tumors. Collectively, this study identifies a novel mechanism of XAF1-mediated tumor suppression, uncovering XAF1 as a feedback coactivator of IRF-1 under stressful conditions.

Overexpression of histone methyltransferase NSD in Drosophila induces apoptotic cell death via the Jun-N-terminal kinase pathway

The nuclear receptor-binding SET domain protein gene (NSD) family encodes a group of highly conserved SET domain-containing histone lysine methyltransferases that are important in multiple aspects of development in various organisms. The association of NSD1 duplications has been reported with growth retardation diseases in humans. In this study, to gain insight into the molecular mechanisms by which the overexpression of NSD1 influences the disease progression, we analyzed the gain-of-function mutant phenotypes of the Drosophila NSD using the GAL4/UAS system. Ubiquitous overexpression of NSD in the fly caused developmental delay and reduced body size at the larval stage, resulting in pupal lethality. Moreover, targeted overexpression in various developing tissues led to significant phenotype alterations, and the gain-of-function phenotypes were rescued by NSD RNAi knockdown. We also demonstrated that NSD overexpression not only enhanced the transcription of pro-apoptotic genes but also activated caspase. The atrophied phenotype of NSD-overexpressing wing was strongly suppressed by a loss-of-function mutation in hemipterous, which encodes a Drosophila Jun N-terminal kinase. Taken together, our findings suggest that NSD induces apoptosis via the activation of JNK, and thus contributes to the understanding of the molecular mechanisms involved in NSD1-related diseases in humans.

Sp1 phosphorylation by ATM downregulates BER and promotes cell elimination in response to persistent DNA damage.

ATM (ataxia-telangiectasia mutated) is a central molecule for DNA quality control. Its activation by DNA damage promotes cell-cycle delay, which facilitates DNA repair prior to replication. On the other hand, persistent DNA damage has been implicated in ATM-dependent cell death via apoptosis; however, the mechanisms underlying this process remain elusive. Here we find that, in response to persistent DNA strand breaks, ATM phosphorylates transcription factor Sp1 and initiates its degradation. We show that Sp1 controls expression of the key base excision repair gene XRCC1, essential for DNA strand break repair. Therefore, degradation of Sp1 leads to a vicious cycle that involves suppression of DNA repair and further aggravation of the load of DNA damage. This activates transcription of pro-apoptotic genes and renders cells susceptible to elimination via both apoptosis and natural killer cells. These findings constitute a previously unrecognized ‘gatekeeper’ function of ATM as a detector of cells with persistent DNA damage.

Essential but partially redundant roles for POU4F1/Brn-3a and POU4F2/Brn-3b transcription factors in the developing heart

Congenital heart defects contribute to embryonic or neonatal lethality but due to the complexity of cardiac development, the molecular changes associated with such defects are not fully understood. Here, we report that transcription factors (TFs) Brn-3a (POU4F1) and Brn-3b (POU4F2) are important for normal cardiac development. Brn-3a directly represses Brn-3b promoter in cardiomyocytes and consequently Brn-3a knockout (KO) mutant hearts express increased Brn-3b mRNA during mid-gestation, which is linked to hyperplastic growth associated with elevated cyclin D1, a known Brn-3b target gene. However, during late gestation, Brn-3b can cooperate with p53 to enhance transcription of pro-apoptotic genes e.g. Bax, thereby increasing apoptosis and contribute to morphological defects such as non-compaction, ventricular wall/septal thinning and increased crypts/fissures, which may cause lethality of Brn-3a KO mutants soon after birth. Despite this, early embryonic lethality in e9.5 double KO (Brn-3a−/− : Brn-3b−/−) mutants indicate essential functions with partial redundancy during early embryogenesis. High conservation between mammals and zebrafish (ZF) Brn-3b (87%) or Brn-3a (76%) facilitated use of ZF embryos to study potential roles in developing heart. Double morphant embryos targeted with morpholino oligonucleotides to both TFs develop significant cardiac defects (looping abnormalities and valve defects) suggesting essential roles for Brn-3a and Brn-3b in developing hearts.