Transcription Of Specific Target Genes Research Articles

Targeting of STAT5 using the small molecule topotecan hydrochloride suppresses acute myeloid leukemia progression.

Acute myeloid leukemia (AML) is a common type of acute leukemia in adults and relapse is one of the main reasons for treatment failure. FLT3‑ITD mutations are associated with poor prognosis, short disease‑free progression survival and high relapse rates in patients with AML. STAT5 is activated by FLT3‑ITD and drives the pathogenesis of AML. STAT5 activation is usually a hallmark of hematologic malignancies and occurs in ~70% of patients with AML. Moreover, STAT5 is a key molecule which regulates hematopoiesis, and its high expression is closely associated with drug resistance, thus direct targeting of STAT5 for AML is of great clinical value. The present study introduces a new small‑molecule inhibitor that targets STAT5, presenting a promising approach for AML therapy. A high throughput fluorescence polarization (FP) screening system for STAT5 was designed and established, and used to screen an existing compound library to obtain the highly active small molecule inhibitor, topotecan hydrochloride. Topotecan hydrochloride was demonstrated to be an effective inhibitor of STAT5 by molecular docking prediction and cellular thermal shift assay. Topotecan hydrochloride bound to STAT5, inhibiting its dimerization, phosphorylation and transcription of specific target genes. The compound exhibits cellular activity at the nanomolar level and significantly inhibits the proliferation of human AML cell lines and FLT3‑ITD+ AML cells. Furthermore, topotecan hydrochloride has the potential to exert an anti‑tumor effect invivo. Overall, topotecan hydrochloride offers a new opportunity for the treatment of AML and other hematologic malignancies by directly targeting STAT5.

The antiactivator FleN uses an allosteric mechanism to regulate σ54-dependent expression of flagellar genes in Pseudomonas aeruginosa.

Diverse sigma factors associate with the RNA polymerase (RNAP) core enzyme to initiate transcription of specific target genes in bacteria. σ54-Mediated transcription uses AAA+ activators that utilize their ATPase activity for transcription initiation. FleQ is a σ54-dependent master transcriptional regulator of flagellar genes in Pseudomonas aeruginosa. The ATPase activity of FleQ is regulated via a P-loop ATPase, FleN, through protein-protein interaction. We report a high-resolution crystal structure of the AAA+ domain of FleQ in complex with antiactivator FleN. The data reveal that FleN allosterically prevents ATP binding to FleQ. Furthermore, FleN remodels the region of FleQ essential for engagement with σ54 for transcription initiation. Disruption of the conserved protein-protein interface, by mutation, shows motility and transcription defects in vivo and multiflagellate phenotype. Our study provides a detailed mechanism used by monoflagellate bacteria to fine-tune the expression of flagellar genes to form and maintain a single flagellum.

A teosinte-derived allele of a MYB transcription repressor confers multiple disease resistance in maize

Natural alleles that control multiple disease resistance (MDR) are valuable for crop breeding. However, only one MDR gene has been cloned in maize, and the molecular mechanisms of MDR remain unclear in maize. In this study, through map-based cloning we cloned a teosinte-derived allele of a resistance gene, Mexicana lesion mimic 1 (ZmMM1), which causes a lesion mimic phenotype and confers resistance to northern leaf blight (NLB), gray leaf spot (GLS), and southern corn rust (SCR) in maize. Strong MDR conferred by the teosinte allele is linked with polymorphisms in the 3′ untranslated region of ZmMM1 that cause increased accumulation of ZmMM1 protein. ZmMM1 acts as a transcription repressor and negatively regulates the transcription of specific target genes, including ZmMM1-target gene 3 (ZmMT3), which functions as a negative regulator of plant immunity and associated cell death. The successful isolation of the ZmMM1 resistance gene will help not only in developing broad-spectrum and durable disease resistance but also in understanding the molecular mechanisms underlying MDR.

Oxidative Stress Transcriptional Responses of Escherichia coli at GaN Interfaces

Microorganisms regulate their interactions with surfaces by altering the transcription of specific target genes in response to physicochemical surface cues. To assess the influence of surface charge and surface chemistry on the transcriptional oxidative stress response, we evaluated the expression of three genes, oxyS, katE, and sodB from the Gram-negative bacterium, Escherichia coli, after a short exposure to GaN interfaces. We observed that both surface charge and surface chemistry were the factors regulating the transcriptional response of the target genes, which indicates that reactive oxygen species (ROS) generation and the ROS response at the GaN interfaces were affected by changing surface properties. The changes in transcription did not correlate to the surface charge in all cases, indicating that there was an influence from multiple interfacial properties on the interactions. Alteration of the bacterial morphology also was a critical factor in these transcriptional responses to the surface cues. When compared to wild-type E. coli bacteria, bacteria missing either flagella or curli exhibited altered transcriptional profiles of the three oxidative stress genes when exposed to GaN materials. These results indicate that the bacterial flagella and curli modulated the oxidative stress response in different ways. The results of this work add to our understanding of the interactions of microbes at interfaces and will be useful for guiding the development of electronic biointerfaces.

Redefining the Clostridioides difficile σB Regulon: σB Activates Genes Involved in Detoxifying Radicals That Can Result from the Exposure to Antimicrobials and Hydrogen Peroxide.

In many Gram-positive bacteria, the general stress response is regulated at the transcriptional level by the alternative sigma factor sigma B (σB). In C. difficile, σB has been implicated in protection against stressors such as reactive oxygen species (ROS) and antimicrobial compounds. Here, we used an anti-σB antibody to demonstrate time-limited overproduction of σB in C. difficile despite its toxicity at higher cellular concentrations. This toxicity eventually led to the loss of the plasmid used for anhydrotetracycline-induced σB gene expression. Inducible σB overproduction uncouples σB expression from its native regulatory network and allows for the refinement of the previously proposed σB regulon. At least 32% of the regulon was found to consist of genes involved in the response to reactive radicals. Direct gene activation by C. difficile σB was demonstrated through in vitro runoff transcription of specific target genes (cd0350, cd3614, cd3605, and cd2963). Finally, we demonstrated that different antimicrobials and hydrogen peroxide induce these genes in a manner dependent on this sigma factor, using a plate-based luciferase reporter assay. Together, our work suggests that lethal exposure to antimicrobials may result in the formation of toxic radicals that lead to σB-dependent gene activation.IMPORTANCE Sigma B is the alternative sigma factor governing stress response in many Gram-positive bacteria. In C. difficile, a sigB mutant shows pleiotropic transcriptional effects. Here, we determine genes that are likely direct targets of σB by evaluating the transcriptional effects of σB overproduction, provide biochemical evidence of direct transcriptional activation by σB, and show that σB-dependent genes can be activated by antimicrobials. Together, our data suggest that σB is a key player in dealing with toxic radicals.

Conditional Deletion of PGC-1α Results in Energetic and Functional Defects in NK Cells.

SummaryDuring an immune response, natural killer (NK) cells activate specific metabolic pathways to meet the increased energetic and biosynthetic demands associated with effector functions. Here, we found in vivo activation of NK cells during Listeria monocytogenes infection-augmented transcription of genes encoding mitochondria-associated proteins in a manner dependent on the transcriptional coactivator PGC-1α. Using an Ncr1Cre-based conditional knockout mouse, we found that PGC-1α was crucial for optimal NK cell effector functions and bioenergetics, as the deletion of PGC-1α was associated with decreased cytotoxic potential and cytokine production along with altered ADP/ATP ratios. Lack of PGC-1α also significantly impaired the ability of NK cells to control B16F10 tumor growth in vivo, and subsequent gene expression analysis showed that PGC-1α mediates transcription required to maintain mitochondrial activity within the tumor microenvironment. Together, these data suggest that PGC-1α-dependent transcription of specific target genes is required for optimal NK cell function during the response to infection or tumor growth.

Bioinformatic Identification of Chinese Hamster Ovary (CHO) Cold-Shock Genes and Biological Evidence of their Cold-Inducible Promoters.

Lower cultivation temperature dramatically affects cell growth and cellular productivity in Chinese hamster ovary cells (CHO) and is often used in industrial applications with the aim to enhance productivity. Cold-inducible proteins whose activity is induced at lower temperature play an important role in understanding the mechanisms of cold-induced changes in gene expression. One of these mechanisms is increased transcription of specific target genes controlled by sequence elements in cold-inducible promoters. This study provides a list of cold-inducible genes and endogenous cold-inducible promoters of CHO cells. Transcriptome data before and after a temperature shift from 37 to 33°C are analyzed to identify 94 cold-inducible genes, which are highly expressed and have a high fold change in expression after the temperature shift. Cold-inducible promoters are identified from the top ten cold-inducible genes, showing up to 11-fold increased luciferase expression at lowered temperature in transient transfections. Additionally, several common transcription factor binding sites are identified in the top cold-inducible promoter sequences and expression of their corresponding transcription factors over temperature-shift cultivation is evaluated. These may be responsible for enhanced promoter activity under lower temperature and can be used as engineering targets.

HDAC1 Is a Required Cofactor of CBFβ-SMMHC and a Potential Therapeutic Target in Inversion 16 Acute Myeloid Leukemia.

Acute myeloid leukemia (AML) is a neoplastic disease characterized by the uncontrolled proliferation and accumulation of immature myeloid cells. A common mutation in AML is the inversion of chromosome 16 [inv (16)], which generates a fusion between the genes for core binding factor beta (CBFB) and smooth muscle myosin heavy chain gene (MYH11), forming the oncogene CBFB-MYH11. The expressed protein, CBFβ-SMMHC, forms a heterodimer with the key hematopoietic transcription factor RUNX1. Although CBFβ-SMMHC was previously thought to dominantly repress RUNX1, recent work suggests that CBFβ-SMMHC functions together with RUNX1 to activate transcription of specific target genes. However, the mechanism of this activity or a requirement for additional cofactors is not known. Here, we show that the epigenetic regulator histone deacetylase 1 (HDAC1) forms a complex with CBFβ-SMMHC, colocalizes with RUNX1 and CBFβ-SMMHC on the promoters of known fusion protein target genes, and that Hdac1 is required for expression of these genes. These results imply that HDAC1 is an important component of the CBFβ-SMMHC transcriptional complex, and that leukemia cells expressing the fusion protein may be sensitive to treatment with HDAC1 inhibitors. Using a knock-in mouse model expressing CBFβ-SMMHC, we found that in vivo treatment with the HDAC1 inhibitor entinostat decreased leukemic burden, and induced differentiation and apoptosis of leukemia cells. Together, these results demonstrate that HDAC1 is an important cofactor of CBFβ-SMMHC and a potential therapeutic target in inv (16) AML. IMPLICATIONS: This report describes a novel role for HDAC1 as a cofactor for the leukemogenic fusion protein CBFβ-SMMHC and shows that inhibitors of HDAC1 effectively target leukemia cells expressing the fusion protein in vivo.

Gamma secretase dependent release of the CD44 cytoplasmic tail upregulates IFI16 in cd44-/- tumor cells, MEFs and macrophages.

The adhesion molecule and co-receptor of receptor tyrosine kinases, CD44, is expressed in all cells of the immune system, but also in numerous non-immune cells. CD44 plays roles in the cellular response to different pathogens. The molecular actions of CD44 during these processes are by and large still unknown. The CD44 molecule undergoes a sequential proteolytic cleavage which leads to the release of a soluble intracellular domain (CD44-ICD). Previous reports had shown that the CD44-ICD is taken up into the nucleus where it enhances transcription of specific target genes. By RNA profiling we identified a CD44-dependent transcriptional increase of interferon-responsive genes, among them IFI16. IFI16 is important in the innate immune response. It senses and binds pathogenic DNA and, together with cGAS, activates the cGAS-cGAMP-STING pathway and induces the expression of genes relevant for the response, e.g. IFN-β. Our results show that the enhancement of IFI16 expression depended on CD44 cleavage. A CD44-negative tumor cell line, embryonic fibroblasts and bone marrow-derived macrophages from cd44-/- mice were reduced in their response to IFN-γ, to viral DNA fragments and to Listeria monocytogenes infection. We could rescue the deficiency of CD44 negative RPM-MC cells and cd44-/- MEFs by expressing only the soluble CD44-ICD in the absence of any other CD44 domain. Expression of the CD44-ICD carrying a mutation that prevented the uptake into the nucleus, could not rescue the absence of CD44. This molecular aspect of regulation by CD44 may explain part of the immune phenotypes of mice with cd44 gene disruption.

Inhibition of p53 prevents diabetic cardiomyopathy by preventing early-stage apoptosis and cell senescence, reduced glycolysis, and impaired angiogenesis

Elevated tumor suppressor p53 expression has been associated with heart diseases, including the diabetic heart. However, its precise role in the pathogenesis of diabetic cardiomyopathy (DCM) remains unclear. We hypothesized that the development of DCM is attributed to up-regulated p53-mediated both early cardiac cell death and persistent cell senescence, glycolytic and angiogenetic dysfunctions. The present study investigated the effect of p53 inhibition with its specific inhibitor pifithrin-α (PFT-α) on the pathogenesis of DCM and its associated mechanisms. Type 1 diabetes was induced with multiple low doses of streptozotocin. Both hyperglycemic and age-matched control mice were treated with and without PFT-α five times a week for 2 months and then sacrificed at 3 and 6 months post-diabetes. Treatment with PFT-α significantly prevented the progression of diabetes-induced cardiac remodeling and dysfunction (i.e., DCM). Mechanistically, the inhibition of p53 prevented the cardiac apoptosis during early-stage diabetes (0.5 month), attenuated diabetes-induced cell senescence (3 and 6 months), and improved both glycolytic and angiogenic defects by increasing hypoxia-induced factor (HIF)-1α protein stability and upregulating HIF-1α transcription of specific target genes at 3 and 6 months after diabetes. Therefore, the targeted inhibition of p53 in diabetic individuals may provide a novel approach for the prevention of DCM.

Improvement of synaptic plasticity by pharmacological activation of RXR nuclear receptors is PPARα dependent.

Event Abstract Back to Event Improvement of synaptic plasticity by pharmacological activation of RXR nuclear receptors is PPARα dependent. Nathalie PIERROT1, 2*, Laurence Ris3, Ilie-Cosmin STANCU STANCU4, Karelle Leroy5, Pascal Kienlen-Campard1, Philippe Gailly1, Jean-Pierre Brion5, Ilse Dewachter4* and Jean-Noël Octave1 1 Université Catholique de Louvain, Belgium 2 Institute of Neuroscience, Catholic University of Leuven, Belgium 3 University of Mons, Belgium 4 University of Hasselt, Belgium 5 Free University of Brussels, Belgium Retinoid X receptors (RXRs) are receptors belonging to the nuclear receptor superfamily of ligand-dependent transcription factors, containing different members including the Peroxisome Proliferator-Activated Receptors (PPARs). These receptors regulate the transcription of target genes through their binding with sequence-specific elements located in gene promoters. Activation of PPARs, which form obligatory heterodimers with RXRs, stimulates the transcription of specific target genes encoding proteins involved in numerous biological processes such as reproduction, development, adipogenesis, energy balance, lipid and glucose biosynthesis and inflammation. Interestingly, a potential involvement of RXRs in neuronal activity was recently proposed since activation of RXRs with specific ligands improves behaviour and cognition in various mouse models of neurodegenerative diseases. However, the mechanisms involved are not fully understood. We have analyzed how bexarotene-mediated activation of RXRs nuclear receptors could modulate synaptic plasticity, an activity-dependent change in synaptic strength in the hippocampus considered as a prominent mechanism underlying learning and memory formation in the mammalian brain. By measuring long-term potentiation (LTP) at hippocampal CA3-CA1 synapses, we observed that activation of RXRs improved hippocampal synaptic plasticity in a transgenic mouse model with cognitive deficits by specifically increasing the expression of the GluA1 subunit of the AMPA receptors. This upregulation of GluA1 expression together with improvement of hippocampal synaptic plasticity induced by activation of RXRs were completely abolished in the absence of PPARalpha. These results indicate that improvement of synaptic functions induced by activation of RXRs is PPARalpha dependent. Keywords: Nuclear receptors (LXR, PPAR, RXR), synaptic plasiticty, LTP (Long Term Potentiation), glutamate receptor, Hippocampus Conference: Belgian Brain Congress 2018 — Belgian Brain Council, LIEGE, Belgium, 19 Oct - 19 Oct, 2018. Presentation Type: e-posters Topic: NOVEL STRATEGIES FOR NEUROLOGICAL AND MENTAL DISORDERS: SCIENTIFIC BASIS AND VALUE FOR PATIENT-CENTERED CARE Citation: PIERROT N, Ris L, STANCU I, Leroy K, Kienlen-Campard P, Gailly P, Brion J, Dewachter I and Octave J (2019). Improvement of synaptic plasticity by pharmacological activation of RXR nuclear receptors is PPARα dependent.. Front. Neurosci. Conference Abstract: Belgian Brain Congress 2018 — Belgian Brain Council. doi: 10.3389/conf.fnins.2018.95.00017 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Jul 2018; Published Online: 17 Jan 2019. * Correspondence: PhD. Nathalie PIERROT, Université Catholique de Louvain, Louvain-la-Neuve, Belgium, nathalie.pierrot@uclouvain.be Prof. Ilse Dewachter, University of Hasselt, Hasselt, Limburg, 3500, Belgium, ilse.dewachter@uhasselt.be Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Nathalie PIERROT Laurence Ris Ilie-Cosmin STANCU STANCU Karelle Leroy Pascal Kienlen-Campard Philippe Gailly Jean-Pierre Brion Ilse Dewachter Jean-Noël Octave Google Nathalie PIERROT Laurence Ris Ilie-Cosmin STANCU STANCU Karelle Leroy Pascal Kienlen-Campard Philippe Gailly Jean-Pierre Brion Ilse Dewachter Jean-Noël Octave Google Scholar Nathalie PIERROT Laurence Ris Ilie-Cosmin STANCU STANCU Karelle Leroy Pascal Kienlen-Campard Philippe Gailly Jean-Pierre Brion Ilse Dewachter Jean-Noël Octave PubMed Nathalie PIERROT Laurence Ris Ilie-Cosmin STANCU STANCU Karelle Leroy Pascal Kienlen-Campard Philippe Gailly Jean-Pierre Brion Ilse Dewachter Jean-Noël Octave Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Retinoic Acid Signaling in P19 Stem Cell Differentiation.

Retinoic acid (RA), especially all-trans retinoic acid is the most potent natural metabolite of vitamin A. RA is involved in a variety of biological functions including embryogenesis, cell differentiation and apoptosis. RA acts through its nuclear receptors to induce transcription of specific target genes. Mouse P19 embryonic carcinoma (EC) stem cells (ES) are one of the most studied in vitro systems for RA-induced differentiation. P19 ES cells can differentiate to endodermal-like, mesodermal-like, and neuronal-like phenotypes in response to specific morphogens including RA and dimethyl sulfoxide (DMSO). At low concentrations, RA directs P19 ES cells to differentiate into cells displaying an endodermal phenotype, whereas at higher concentrations it induces differentiation to neuroectoderm. In the past, many RA---regulated genes have been discovered in EC and ES cells and efforts are ongoing to elucidate the exact mechanisms of RA-induced ES cell differentiation and apoptosis. In the RA-triggered differentiation process of the P19 ES cells, several proteins belonging to different families participate, some being obligatory while others, dispensable. Revealing the mechanisms behind RA-induced effects on ES cells has a bearing on understanding how cells proliferate, differentiate and undergo apoptosis that can provide greater insight into cancer biology and therapy. In addition to summarizing the reports on gene/protein targets of RA in stem cells, the signaling pathways driven by some of the specific class of proteins in the presence or absence of RA in P19 ES cell differentiation, especially to an endodermal phenotype, are the focus of this review.

Modulation of light-driven arousal by LIM-homeodomain transcription factor Apterous in large PDF-positive lateral neurons of the Drosophila brain.

Apterous (Ap), the best studied LIM-homeodomain transcription factor in Drosophila, cooperates with the cofactor Chip (Chi) to regulate transcription of specific target genes. Although Ap regulates various developmental processes, its function in the adult brain remains unclear. Here, we report that Ap and Chi in the neurons expressing PDF, a neuropeptide, play important roles in proper sleep/wake regulation in adult flies. PDF-expressing neurons consist of two neuronal clusters: small ventral-lateral neurons (s-LNvs) acting as the circadian pacemaker and large ventral-lateral neurons (l-LNvs) regulating light-driven arousal. We identified that Ap localizes to the nuclei of s-LNvs and l-LNvs. In light-dark (LD) cycles, RNAi knockdown or the targeted expression of dominant-negative forms of Ap or Chi in PDF-expressing neurons or l-LNvs promoted arousal. In contrast, in constant darkness, knockdown of Ap in PDF-expressing neurons did not promote arousal, indicating that a reduced Ap function in PDF-expressing neurons promotes light-driven arousal. Furthermore, Ap expression in l-LNvs showed daily rhythms (peaking at midnight), which are generated by a direct light-dependent mechanism rather than by the endogenous clock. These results raise the possibility that the daily oscillation of Ap expression in l-LNvs may contribute to the buffering of light-driven arousal in wild-type flies.

Long noncoding RNA linc00598 regulates CCND2 transcription and modulates the G1 checkpoint.

Data derived from genomic and transcriptomic analyses have revealed that long noncoding RNAs (lncRNAs) have important roles in the transcriptional regulation of various genes. Recent studies have identified the mechanism underlying this function. To date, a variety of noncoding transcripts have been reported to function in conjunction with epigenetic regulator proteins. In this study, we investigated the function of linc00598, which is transcribed by a genomic sequence on chromosome 13, downstream of FoxO1 and upstream of COG6. Microarray analysis showed that linc00598 regulates the transcription of specific target genes, including those for cell cycle regulators. We discovered that linc00598 regulates CCND2 transcription through modulation of the transcriptional regulatory effect of FoxO1 on the CCND2 promoter. Moreover, we observed that knockdown of linc00598 induced G0/G1 cell cycle arrest and inhibited proliferation. These data indicate that linc00598 plays an important role in cell cycle regulation and proliferation through its ability to regulate the transcription of CCND2.

Oct-1, to go or not to go? That is the PolII question

The Oct transcription factors recognise an octamer DNA element from which they regulate transcription of specific target genes. Oct-1 is the only member of the subfamily that is ubiquitously expressed and has a wide role in transcriptional control. Through interaction with various partner proteins, Oct-1 can modulate accessibility to the chromatin to recruit the transcription machinery and form the pre-initiation complex. The recruited PolII is induced to initiate transcription and stalled until elongation is triggered on interaction with signalling transcription factors. In this way, Oct-1 can fulfil general roles in transcription by opening the chromatin as well as transduce extracellular signals by relaying activation through various interacting partners. The emerging picture of Oct-1 is that of a complex and versatile transcription factor with fundamental functions in cell homeostasis and signal response in general as well as cell specific contexts. This article is part of a Special Issue entitled: The Oct Transcription Factor Family, edited by Dr. Dean Tantin.

Wnt/β-catenin signaling in bone marrow niche.

The bone marrow (BM) niche is a specific physiological environment for hematopoietic and non-hematopoietic stem cells (HSCs). Several signaling pathways (including Wnt/β-catenin) regulate various aspects of stem cell growth, function and death in the BM niche. In addition, the canonical Wnt pathway is crucial for directing self-renewal and differentiation as important mechanisms in many types of stem cells. We review the role of the Wnt/β-catenin pathway in the BM niche and its importance in stem cells. Relevant literature was identified by a PubMed search (1997-2014) of English-language literature by using the following keywords: BM niche, Wnt/β-catenin signaling, osteoblast, osteoclast and bone disease. The Wnt/β-catenin pathway regulates the stability of the β-catenin proto-oncogene. The stabilized β-catenin then translocates to the nucleus, forming a β-catenin-TCF/LEF complex regulating the transcription of specific target genes. Stem cells require β-catenin to mediate their response to Wnt signaling for maintenance and transition from the pluripotent state during embryogenesis. In adult stem cells, Wnt signaling functions at various hierarchical levels to contribute to the specification of the diverse tissues. Aberrant Wnt/β-catenin signaling and its downstream transcriptional regulators are observed in several malignant stem cells and human cancers. Because Wnt signaling can maintain stem cells and cancer cells, the ability to modulate the Wnt pathway either positively or negatively may be of therapeutic relevance. The controlled activation of Wnt signaling might allow us to enhance stem and progenitor cell activity when regeneration is needed.

Abstract 997: Loss of Miz-1 increases latency of T-ALL by preventing induction of autophagy

Abstract The Myc-Interacting Zinc-finger protein-1 (Miz-1) can bind to the proto-oncogene c-Myc and the Miz-1/c-Myc complex can regulate the transcription of specific target genes. Miz-1 contains a BTB/POZ domain and thirteen zinc finger domains that mediate binding to DNA and its interaction with partner proteins. While Miz-1 itself functions as a transcriptional transactivator, it enables c-Myc to act as a transcriptional repressor of genes negatively regulating cell cycle progression. We have previously reported that Miz-1 plays an essential role during early stages of T cell development by regulating the translation of p53 via the ribosomal protein L22. Based on this function of Miz-1 in T cell development, we have decided to investigate a potential role of Miz-1 in the development of T cell leukemia or lymphoma. We have used several different experimental models to induce T-ALL in mice that are conditionally deficient for Miz-1. We used non-acute transforming retroviruses, such as Moloney Murine Leukemia Virus (MMLV), which induces T-cell leukemia by activating known oncogenes, including Gfi1, Pim1 and c-Myc via proviral insertion. We also used ENU mutagenesis, which induces T-cell leukemia through activation of the Ras pathway. We observed that Miz-1 is required for the development of T cell leukemia regardless of whether it is induced by MMLV or ENU, since Miz-1-deficient mice succumb to the disease with a significantly longer latency period than WT animals. Importantly, during tumorigenesis a strong counter selection occurs against the loss of Miz-1. Interestingly, MycV394D transgenic animals, carrying a c-Myc protein that can no longer interact directly with Miz-1, develop tumors at a rate comparable to WT mice, indicating that a function of Miz-1 is required for T cell tumorigenesis that is independent of its interaction with c-Myc. Transcriptome analyses showed that Miz-1 deficiency correlated with a decrease of expression in autophagy-related genes, consistent with earlier reports that Miz-1 is necessary for the induction of this pathway. ChIP-seq confirmed that Miz-1 binds to the promoters of these autophagy-related genes, indicating that these genes are activated in the presence of Miz-1, also consistent with previous reports. Furthermore, Miz-1-deficient tumors undergo higher levels of apoptosis than WT tumors. Based on these results, we conclude that Miz-1 is essential for the efficient development of T-ALL and that loss of Miz-1 significantly hinders T-ALL development in part through the inability of these cells to induce autophagy. Citation Format: Marissa Rashkovan, Charles Vadnais, Julie Ross, Jennifer Fraszczak, Tarik Moroy. Loss of Miz-1 increases latency of T-ALL by preventing induction of autophagy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 997. doi:10.1158/1538-7445.AM2015-997

Covering the Cover

Covering the Cover

SWI/SNF chromatin-remodeling enzymes Brahma-related gene 1 (BRG1) and Brahma (BRM) are dispensable in multiple models of postnatal angiogenesis but are required for vascular integrity in infant mice.

BackgroundMammalian SWItch/Sucrose NonFermentable (SWI/SNF) adenosine triphosphate (ATP)‐dependent chromatin‐remodeling complexes play important roles in embryonic vascular development by modulating transcription of specific target genes. We sought to determine whether SWI/SNF complexes likewise impact postnatal physiological and pathological angiogenesis.Methods and ResultsBrahma‐related gene 1 (BRG1) and Brahma gene (BRM) are ATPases within mammalian SWI/SNF complexes and are essential for the complexes to function. Using mice with vascular‐specific mutations in Brg1 or with a global mutation in Brm, we employed 3 models to test the role of these ATPases in postnatal angiogenesis. We analyzed neonatal retinal angiogenesis, exercise‐induced angiogenesis in adult quadriceps muscles, and tumor angiogenesis in control and mutant animals. We found no evidence of defective angiogenesis in Brg1 or Brm mutants using these 3 models. Brg1/Brm double mutants likewise show no evidence of vascular defects in the neonatal retina or tumor angiogenesis models. However, 100% of Brg1/Brm‐double mutants in which Brg1 deletion is induced at postnatal day 3 (P3) die by P19 with hemorrhaging in the small intestine and heart.ConclusionsDespite their important roles in embryonic vascular development, SWI/SNF chromatin‐remodeling complexes display a surprising lack of participation in the 3 models of postnatal angiogenesis we analyzed. However, these complexes are essential for maintaining vascular integrity in specific tissue beds before weaning. These findings highlight the temporal and spatial specificity of SWI/SNF activities in the vasculature and may indicate that other chromatin‐remodeling complexes play redundant or more essential roles during physiological and pathological postnatal vascular development.

Ligand binding and functional selectivity of L-tryptophan metabolites at the mouse aryl hydrocarbon receptor (mAhR).

The aryl hydrocarbon receptor (AhR) is a nuclear receptor regulating a wide range of biological and toxicological effects. Metabolites of L-tryptophan are able to bind and activate AhR, providing a link between tryptophan catabolism and a novel mechanism of protective tolerance, referred to as "disease tolerance". The notion that pharmacologic modulation of genes associated with endotoxin tolerance would be beneficial in clinical settings dominated by acute hyperinflammatory responses to infection thrusts AhR into the limelight as an interesting druggable target. Combining homology modeling, docking studies, and molecular dynamic simulations with mutagenesis experiments and gene profiling, in this work we report that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and two different L-tryptophan metabolites, namely L-Kynurenine and FICZ (6-formylindolo[3,2-b]carbazole), are able to bind to mAhR, exploiting different key interactions with distinct set of fingerprint residues. As a result, they stabilize different conformations of mAhR that, in turn, selectively regulate downstream signaling and transcription of specific target genes. Collectively, these results open new avenues for the design and development of selective AhR modulators that, by targeting specific receptor conformations associated with specific AhR functions, may offer novel therapeutic opportunities in infectious diseases and other morbidity that may be associated with the receptor.