Description: Toxins play a major role in the pathogenesis of Bacillus anthracis by subverting the host defenses. However, besides toxins, B. anthracis expresses effector proteins, whose role in pathogenesis are yet to be investigated. Here we present that suppressor-of-variegation, enhancer-of-zeste, trithorax protein from B. anthracis (BaSET) methylates human histone H1, resulting in repression of NF-κB functions. Notably, BaSET is secreted and undergoes nuclear translocation to enhance H1 methylation in B. anthracis-infected macrophages. Compared with wild type Sterne, delayed growth kinetics and altered septum formation were observed in the BaSET knock-out (BaΔSET) bacilli. Uncontrolled BaSET expression during complementation of the BaSET gene in BaΔSET partially restored growth during stationary phase but resulted in substantially shorter bacilli throughout the growth cycle. Importantly, in contrast to Sterne, the BaΔSET B. anthracis is avirulent in a lethal murine bacteremia model of infection. Collectively, BaSET is required for repression of host transcription as well as proper B. anthracis growth, making it a potentially unique virulence determinant.

Description: Prostate cancer (PCa) stem/progenitor cells are known to have higher chemoresistance than non-stem/progenitor cells, but the underlying molecular mechanism remains unclear. We found the expression of testicular nuclear receptor 4 (TR4) is significantly higher in PCa CD133+ stem/progenitor cells compared with CD133− non-stem/progenitor cells. Knockdown of TR4 levels in the established PCa stem/progenitor cells and the CD133+ population of the C4-2 PCa cell line with lentiviral TR4 siRNA led to increased drug sensitivity to the two commonly used chemotherapeutic drugs, docetaxel and etoposide, judging from significantly reduced IC50 values and increased apoptosis in the TR4 knockdown cells. Mechanism dissection studies found that suppression of TR4 in these stem/progenitor cells led to down-regulation of Oct4 expression, which, in turn, down-regulated the IL-1 receptor antagonist (IL1Ra) expression. Neutralization experiments via adding these molecules into the TR4 knockdown PCa stem/progenitor cells reversed the chemoresistance, suggesting that the TR4-Oct4-IL1Ra axis may play a critical role in the development of chemoresistance in the PCa stem/progenitor cells. Together, these studies suggest that targeting TR4 may alter chemoresistance of PCa stem/progenitor cells, and this finding provides the possibility of targeting TR4 as a new and better approach to overcome the chemoresistance problem in PCa therapeutics.

Description: Embryonic stem cells (ESCs) are considered to be a promising cell source for regenerative medicine because of their unlimited capacity for self-renewal and differentiation. However, little is known about the innate immunity in ESCs and ESC-derived cells. We investigated the responses of mouse (m)ESCs to three types of live viruses as follows: La Crosse virus, West Nile virus, and Sendai virus. Our results demonstrated mESCs were susceptible to viral infection, but they were unable to express type I interferons (IFNα and IFNβ, IFNα/β), which differ from fibroblasts (10T1/2 cells) that robustly express IFNα/β upon viral infections. The failure of mESCs to express IFNα/β was further demonstrated by treatment with polyIC, a synthetic viral dsRNA analog that strongly induced IFNα/β in 10T1/2 cells. Although polyIC transiently inhibited the transcription of pluripotency markers, the stem cell morphology was not significantly affected. However, polyIC can induce dsRNA-activated protein kinase in mESCs, and this activation resulted in a strong inhibition of cell proliferation. We conclude that the cytosolic receptor dsRNA-activated protein kinase is functional, but the mechanisms that mediate type I IFN expression are deficient in mESCs. This conclusion is further supported by the findings that the major viral RNA receptors are either expressed at very low levels (TLR3 and MDA5) or may not be active (retinoic acid-inducible gene I) in mESCs.

Description: Huntington disease (HD) is a neurodegenerative disorder characterized by progressive motor impairment and cognitive alterations. Hereditary HD is primarily caused by the expansion of a CAG trinucleotide repeat in the huntingtin (Htt) gene, which results in the production of mutant huntingtin protein (mHTT) with an expanded amino-terminal polyglutamine (poly(Q)) stretch. Besides pathological mHTT aggregation, reduced brain-derived neurotrophic factor (BDNF) levels, impaired neurotrophin signaling, and compromised mitochondrial functions also contribute to the deleterious progressive etiology of HD. As a well tolerated Food and Drug Administration-approved antidepressant, amitriptyline (AMI) has shown efficacy in treating neurodegenerative murine models via potentiation of BDNF levels and amelioration of alterations in neurotrophin signaling pathways. In this study, we observed profound improvements in the motor coordination of AMI-treated N171-82Q HD model mice. The beneficial effects of AMI treatment were associated with its ability to reduce mHTT aggregation, potentiation of the BDNF-TrkB signaling system, and support of mitochondrial integrity and functionality. Our study not only provides preclinical evidence for the therapeutic potency of AMI in treating HD, but it also represents an important example of the usefulness of additional pharmacogenomic profiling of pre-existing drugs for novel therapeutic effects with often intractable pathological scenarios.

Description: NUT midline carcinoma (NMC) is a rare but highly aggressive cancer typically caused by the translocation t(15;19), which results in the formation of the BRD4-NUT fusion oncoprotein. Previous studies have demonstrated that fusion of the NUT protein with the double bromodomains of BRD4 may significantly alter the cellular gene expression profile to contribute to NMC tumorigenesis. However, the mechanistic details of this BRD4-NUT function remain poorly understood. In this study, we examined the NUT function in transcriptional regulation by targeting it to a LacO transgene array integrated in U2OS 2-6-3 cells, which allow us to visualize how NUT alters the in situ gene transcription dynamic. Using this system, we demonstrated that the NUT protein tethered to the LacO locus recruits p300/CREB-binding protein (CBP), induces histone hyperacetylation, and enriches BRD4 to the transgene array chromatin foci. We also discovered that, in BRD4-NUT expressed in NMC cells, the NUT moiety of the fusion protein anchored to chromatin by the double bromodomains also stimulates histone hyperacetylation, which causes BRD4 to bind tighter to chromatin. Consequently, multiple BRD4-interacting factors are recruited to the NUT-associated chromatin locus to activate in situ transgene expression. This gene transcription function was repressed by either expression of a dominant negative inhibitor of the p300-NUT interaction or treatment with (+)-JQ1, which dissociates BRD4 from the LacO chromatin locus. Our data support a model in which BRD4-NUT-stimulated histone hyperacetylation recruits additional BRD4 and interacting partners to support transcriptional activation, which underlies the BRD4-NUT oncogenic mechanism in NMC.

Description: Prenylated flavonoids are attractive specialized metabolites with a wide range of biological activities and are distributed in several plant families. The prenylation catalyzed by prenyltransferases represents a Friedel-Crafts alkylation of the flavonoid skeleton in the biosynthesis of natural prenylated flavonoids and contributes to the structural diversity and biological activities of these compounds. To date, all identified plant flavonoid prenyltransferases (FPTs) have been identified in Leguminosae. In the present study two new FPTs, Morus alba isoliquiritigenin 3′-dimethylallyltransferase (MaIDT) and Cudrania tricuspidata isoliquiritigenin 3′-dimethylallyltransferase (CtIDT), were identified from moraceous plants M. alba and C. tricuspidata, respectively. MaIDT and CtIDT shared low levels of homology with the leguminous FPTs. MaIDT and CtIDT are predicted to be membrane-bound proteins with predicted transit peptides, seven transmembrane regions, and conserved functional domains that are similar to other homogentisate prenyltransferases. Recombinant MaIDT and CtIDT were able to regioselectively introduce dimethylallyl diphosphate into the A ring of three flavonoids with different skeleton types (chalcones, isoflavones, and flavones). Phylogenetic analysis revealed that MaIDT and CtIDT are distantly related to their homologs in Leguminosae, which suggests that FPTs in Moraceae and Leguminosae might have evolved independently. MaIDT and CtIDT represent the first two non-Leguminosae FPTs to be identified in plants and could thus lead to the identification of additional evolutionarily varied FPTs in other non-Leguminosae plants and could elucidate the biosyntheses of prenylated flavonoids in various plants. Furthermore, MaIDT and CtIDT might be used for regiospecific prenylation of flavonoids to produce bioactive compounds for potential therapeutic applications due to their high efficiency and catalytic promiscuity.

Description: Ascl2, a basic helix-loop-helix transcription factor, is a downstream target of WNT signaling that controls the fate of intestinal cryptic stem cells and colon cancer progenitor cells. However, its involvement in colon cancer and downstream molecular events is largely undefined; in particular, the mechanism by which Ascl2 regulates the plasticity of epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) programs in colon cancer cells remains unknown. In this study, we systematically demonstrate that Ascl2 loss of function in colon cancer cells promotes MET by derepressing the expression of microRNA (miR)-200s (i.e. miR-200b, miR-200a, miR-429, miR-200c, and miR-141) and further activating their expression through a transcriptional mechanism that involves direct binding to the most proximal E-box (E-box2) in the miR-200b-a-429 promoter. Activation of miR-200s due to Ascl2 deficiency led to the inhibition of ZEB1/2 expression and the alteration of epithelial and mesenchymal features. Transfection of miR-200b, miR-200a, and miR-429 inhibitors into Ascl2-deficient colon cancer cells promoted the epithelial-mesenchymal transition in a reversible manner. Transfection of miR-200a or miR-429 inhibitors into Ascl2-deficient colon cancer cells increased cellular proliferation and migration. Ascl2 mRNA levels and the miR-200a, miR-200b, miR-200c, miR-141, or miR-429 levels in the colon cancerous samples were inversely correlated. These results provide the first evidence of a link between Ascl2 and miR-200s in the regulation of EMT-MET plasticity in colon cancer.

Description: Idelalisib (also known as GS-1101, CAL-101, IC489666, and Zydelig) is a PI3Kδ inhibitor that has recently been approved for the treatment of several hematological malignancies. Given its use in human diseases, we needed a clear picture of how idelalisib binds to and inhibits PI3Kδ. Our data show that idelalisib is a potent and selective inhibitor of the kinase activity of PI3Kδ. A kinetic characterization clearly demonstrated ATP-competitive inhibition, and several additional biochemical and biophysical assays showed that the compound binds reversibly and noncovalently to the kinase. A crystal structure of idelalisib bound to the p110δ subunit of PI3Kδ furthers our understanding of the binding interactions that confer the potency and selectivity of idelalisib.

Description: Brain accumulation of neurotoxic amyloid β (Aβ) peptide because of increased processing of amyloid precursor protein (APP), resulting in loss of synapses and neurodegeneration, is central to the pathogenesis of Alzheimer disease (AD). Therefore, the identification of molecules that regulate Aβ generation and those that cause synaptic damage is crucial for future therapeutic approaches for AD. We demonstrated previously that COPS5 regulates Aβ generation in neuronal cell lines in a RanBP9-dependent manner. Consistent with the data from cell lines, even by 6 months, COPS5 overexpression in APΔE9 mice (APΔE9/COPS5-Tg) significantly increased Aβ40 levels by 32% (p 〈 0.01) in the cortex and by 28% (p 〈 0.01) in the hippocampus, whereas the increases for Aβ42 were 37% (p 〈 0.05) and 34% (p 〈 0.05), respectively. By 12 months, the increase was even more robust. Aβ40 levels increased by 63% (p 〈 0.001) in the cortex and by 65% (p 〈 0.001) in the hippocampus. Similarly, Aβ42 levels were increased by 69% (p 〈 0.001) in the cortex and by 71% (p 〈 0.011) in the hippocampus. Increased Aβ levels were translated into an increased amyloid plaque burden both in the cortex (54%, p 〈 0.01) and hippocampus (64%, p 〈 0.01). Interestingly, COPS5 overexpression increased RanBP9 levels in the brain, which, in turn, led to increased amyloidogenic processing of APP, as reflected by increased levels of sAPPβ and decreased levels of sAPPα. Furthermore, COPS5 overexpression reduced spinophilin in both the cortex (19%, p 〈 0.05) and the hippocampus (20%, p 〈 0.05), leading to significant deficits in learning and memory skills. Therefore, like RanBP9, COPS5 also plays a pivotal role in amyloid pathology in vivo.

Description: The NH2-terminal region (residues 1–543) of the cardiac ryanodine receptor (RyR2) harbors a large number of mutations associated with cardiac arrhythmias and cardiomyopathies. Functional studies have revealed that the NH2-terminal region is involved in the activation and termination of Ca2+ release. The three-dimensional structure of the NH2-terminal region has recently been solved. It is composed of three domains (A, B, and C). However, the roles of these individual domains in Ca2+ release activation and termination are largely unknown. To understand the functional significance of each of these NH2-terminal domains, we systematically deleted these domains and assessed their impact on caffeine- or Ca2+-induced Ca2+ release and store overload-induced Ca2+ release (SOICR) in HEK293 cells. We found that all deletion mutants were capable of forming caffeine- and ryanodine-sensitive functional channels, indicating that the NH2-terminal region is not essential for channel gating. Ca2+ release measurements revealed that deleting domain A markedly reduced the threshold for SOICR termination but had no effect on caffeine or Ca2+ activation or the threshold for SOICR activation, whereas deleting domain B substantially enhanced caffeine and Ca2+ activation and lowered the threshold for SOICR activation and termination. Conversely, deleting domain C suppressed caffeine activation, abolished Ca2+ activation and SOICR, and diminished protein expression. These results suggest that domain A is involved in channel termination, domain B is involved in channel suppression, and domain C is critical for channel activation and expression. Our data shed new insights into the structure-function relationship of the NH2-terminal domains of RyR2 and the action of NH2-terminal disease mutations.