The rockefeller university

Background & Aims: Hepatitis B virus (HBV) infects and replicates in quiescent hepatocytes, which are deficient in dNTPs, the critical precursors of HBV replication. Most tumor viruses promote dNTP production in host cells by inducing cell proliferation. Although HBV is known as a major cause of hepatocellular carcinoma, it does not lead to cellular proliferation. Instead, HBV acquires dNTPs by activating the expression of the R2 subunit of the Ribonucleotide Reductase (RNR) holoenzyme, the cell cycle gene that is rate-limiting for generation of dNTPs, without inducing the cell cycle. We wished to elucidate the molecular basis of HBV-dependent R2 expression in quiescent cells. Methods: Quiescent HepG2 cells were transduced with an HBV-containing lentiviral vector, and primary human hepatocytes were infected with HBV. DNA damage response and RNR-R2 gene expression were monitored under this condition. Results: We report here that HBV-induced R2 expression is mediated by the E2F1 transcription factor, and that HBV induces E2F1 accumulation, modification and binding to the R2 promoter. We found that Chk1, a known E2F1 kinase that functions in response to DNA damage, was activated by HBV. In cells where Chk1 was pharmacologically inhibited, or depleted by shRNA-mediated knockdown, HBV-mediated R2 expression was severely attenuated. Furthermore, we found that HBV attenuates DNA repair, thus reducing cellular dNTP consumption. Conclusions: Our findings demonstrate that HBV exploits the Chk1-E2F1 axis of the DNA damage response pathway to induce R2 expression in a cell cycle-independent manner. This suggests that inhibition of this pathway may have a therapeutic value for HBV carriers. (C) 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Measurements of the ZZ production cross sections in proton-proton collisions at center-of-mass energies of 7 and 8 TeV are presented. Candidate events for the leptonic decay mode ZZ -> 2l2 nu. where l denotes an electron or a muon, are reconstructed and selected from data corresponding to an integrated luminosity of 5.1 (19.6) fb(-1) at 7 (8) TeV collected with the CMS experiment. The measured cross sections, sigma(pp -> ZZ) = 5.1(1.4)(+1.5) (stat)(-1.1)(+1.4) (syst) +/- 0.1 (lumi) pb at 7 TeV, and 7.2(-0.8)(+0.8) (stat)(1.5)(+1.9) (syst) +/- 0.2 (lumi) pb at 8 TeV, are in good agreement with the standard model predictions with next-to-leading-order accuracy. The selected data are analyzed to search for anomalous triple gauge couplings involving the ZZ final state. In the absence of any deviation from the standard model predictions, limits are set on the relevant parameters. These limits are then combined with the previously published CMS results for ZZ in 4l final states, yielding the most stringent constraints on the anomalous couplings.

DNA double-strand break repair involves phosphorylation of histone variant H2AX ('gamma H2AX'), which accumulates in foci at sites of DNA damage. In current models, the recruitment of multiple DNA repair proteins to gamma H2AX foci depends mainly on recognition of this 'mark' by a single protein, MDC1. However, DNA repair proteins accumulate at gH2AX sites without MDC1, suggesting that other 'readers' of this mark exist. Here, we use a quantitative chemical proteomics approach to profile direct, phospho-selective gamma H2AX binders in native proteomes. We identify gamma H2AX binders, including the DNA repair mediator 53BP1, which we show recognizes gamma H2AX through its BRCT domains. Furthermore, we investigate the targeting of wild-type 53BP1, or a mutant form deficient in gamma H2AX binding, to chromosomal breaks resulting from endogenous and exogenous DNA damage. Our results show how direct recognition of gamma H2AX modulates protein localization at DNA damage sites, and suggest how specific chromatin mark-reader interactions contribute to essential mechanisms ensuring genome stability.

Aberrant viral RNAs produced in infected plant cells serve as templates for the synthesis of dsRNAs. The derived virus-related small interfering RNAs (siRNA) mediate cleavage of viral RNAs by post-transcriptional gene silencing (PTGS), thus blocking virus multiplication. Here, we identified ASYMMETRIC LEAVES2 (AS2) as a new component of plant P body complex which mediates mRNA decapping and degradation. We found that AS2 promotes DCP2 decapping activity, accelerates mRNA turnover rate, inhibits siRNA accumulation and functions as an endogenous suppressor of PTGS. Consistent with these findings, as2 mutant plants are resistant to virus infection whereas AS2 over-expression plants are hypersensitive. The geminivirus nuclear shuttle protein BV1 protein, which shuttles between nuclei and cytoplasm, induces AS2 expression, causes nuclear exit of AS2 to activate DCP2 decapping activity and renders infected plants more sensitive to viruses. These principles of gene induction and shuttling of induced proteins to promote mRNA decapping in the cytosol may be used by viral pathogens to weaken antiviral defenses in host plants.

A search for a heavy Higgs boson in the H -> WW and H -> ZZ decay channels is reported. The search is based upon proton-proton collision data samples corresponding to an integrated luminosity of up to 5.1 fb(-1) at root s = 7 TeV and up to 19.7 fb(-1) at root s = 8 TeV, recorded by the CMS experiment at the CERN LHC. Several final states of the H -> WW and H -> ZZ decays are analyzed. The combined upper limit at the 95% confidence level on the product of the cross section and branching fraction exclude a Higgs boson with standard model-like couplings and decays in the range 145 < m(H) < 1000 GeV. We also interpret the results in the context of an electroweak singlet extension of the standard model.

Studies investigating the causes of autism spectrum disorder (ASD) point to genetic, as well as epigenetic, mechanisms of the disease. Identification of epigenetic processes that contribute to ASD development and progression is of major importance and may lead to the development of novel therapeutic strategies. Here, we identify the bromodomain and extraterminal domain-containing proteins (BETs) as epigenetic regulators of genes involved in ASD-like behaviors in mice. We found that the pharmacological suppression of BET proteins in the brain of young mice, by the novel, highly specific, brain-permeable inhibitor I-BET858 leads to selective suppression of neuronal gene expression followed by the development of an autism-like syndrome. Many of the I-BET858-affected genes have been linked to ASD in humans, thus suggesting the key role of the BET-controlled gene network in the disorder. Our studies suggest that environmental factors controlling BET proteins or their target genes may contribute to the epigenetic mechanism of ASD.

Background: Follicular helper T (T-FH) cells underpin T cell-dependent humoral immunity and the success of most vaccines. T-FH cells also contribute to human immune disorders, such as autoimmunity, immunodeficiency, and malignancy. Understanding the molecular requirements for the generation and function of T-FH cells will provide strategies for targeting these cells to modulate their behavior in the setting of these immunologic abnormalities. Objective: We sought to determine the signaling pathways and cellular interactions required for the development and function of T-FH cells in human subjects. Methods: Human primary immunodeficiencies (PIDs) resulting from monogenic mutations provide a unique opportunity to assess the requirement for particular molecules in regulating human lymphocyte function. Circulating follicular helper T (cT(FH)) cell subsets, memory B cells, and serum immunoglobulin levels were quantified and functionally assessed in healthy control subjects, as well as in patients with PIDs resulting from mutations in STAT3, STAT1, TYK2, IL21, IL21R, IL10R, IFNGR1/2, IL12RB1, CD40LG, NEMO, ICOS, or BTK. Results: Loss-of-function (LOF) mutations in STAT3, IL10R, CD40LG, NEMO, ICOS, or BTK reduced cT(FH) cell frequencies. STAT3 and IL21/R LOF and STAT1 gain-of-function mutations skewed cT(FH) cell differentiation toward a phenotype characterized by overexpression of IFN-gamma and programmed death 1. IFN-gamma inhibited cT(FH) cell function in vitro and in vivo, as corroborated by hypergammaglobulinemia in patients with IFNGR1/2, STAT1, and IL12RB1 LOF mutations. Conclusion: Specific mutations affect the quantity and quality of cT(FH) cells, highlighting the need to assess T-FH cells in patients by using multiple criteria, including phenotype and function. Furthermore, IFN-gamma functions in vivo to restrain T-FH cell-induced B-cell differentiation. These findings shed new light on T-FH cell biology and the integrated signaling pathways required for their generation, maintenance, and effector function and explain the compromised humoral immunity seen in patients with some PIDs.

Two searches for physics beyond the standard model in events containing photons are presented. The data sample used corresponds to an integrated luminosity of 19.7 fb(-1) of proton-proton collisions at root s = 8 TeV, collected with the CMS experiment at the CERN LHC. The analyses pursue different inclusive search strategies. One analysis requires at least one photon, at least two jets, and a large amount of transverse momentum imbalance, while the other selects events with at least two photons and at least one jet, and uses the razor variables to search for signal events. The background expected from standard model processes is evaluated mainly from data. The results are interpreted in the context of general gauge-mediated supersymmetry, with the next-to-lightest supersymmetric particle either a bino- or wino-like neutralino, and within simplified model scenarios. Upper limits at the 95% confidence level are obtained for cross sections as functions of the masses of the intermediate supersymmetric particles.

In a short hairpin RNA screen for genes that affect AKT phosphorylation, we identified the RAB35 small guanosine triphosphatase (GTPase)-a protein previously implicated in endomembrane trafficking-as a regulator of the phosphatidylinositol 3'-OH kinase (PI3K) pathway. Depletion of RAB35 suppresses AKT phosphorylation in response to growth factors, whereas expression of a dominant active GTPase-deficient mutant of RAB35 constitutively activates the PI3K/AKT pathway. RAB35 functions downstream of growth factor receptors and upstream of PDK1 and mTORC2 and copurifies with PI3K in immunoprecipitation assays. Two somatic RAB35 mutations found in human tumors generate alleles that constitutively activate PI3K/AKT signaling, suppress apoptosis, and transform cells in a PI3K-dependent manner. Furthermore, oncogenic RAB35 is sufficient to drive platelet-derived growth factor receptor a to LAMP2-positive endomembranes in the absence of ligand, suggesting that there may be latent oncogenic potential in dysregulated endomembrane trafficking.

Treatment with ionizing radiation (IR) can lead to the accumulation of tumor-infiltrating regulatory T cells (T-reg cells) and subsequent resistance of tumors to radiotherapy. Here we focused on the contribution of the epidermal mononuclear phagocytes Langerhans cells (LCs) to this phenomenon because of their ability to resist depletion by high-dose IR. We found that LCs resisted apoptosis and rapidly repaired DNA damage after exposure to IR. In particular, we found that the cyclin-dependent kinase inhibitor CDKN1A (p21) was overexpressed in LCs and that Cdkn1a(-/-) LCs underwent apoptosis and accumulated DNA damage following IR treatment. Wild-type LCs upregulated major histocompatibility complex class II molecules, migrated to the draining lymph nodes and induced an increase in T-reg cell numbers upon exposure to IR, but Cdkn1a(-/-) LCs did not. Our findings suggest a means for manipulating the resistance of LCs to IR to enhance the response of cutaneous tumors to radiotherapy.