Mutagenesis of hepatitis B virus protein HBx and studies of its interaction with RNA and human proteins

Orientador: Jorg KobargTese (doutorado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: A hepatite B constitui um grave problema de saúde pública. Dados epidemiológicos estimam que aproximadamente 350 milhões de pessoas são portadores do vírus da hepatite B (HBV). Admite-se que a infecção evolui para a cura em média 95% dos casos, entretanto nos portadores crônicos a infecção pode evoluir para cirrose e carcinoma hepatocelular (HCC). Há um crescente acúmulo de evidências que relaciona a proteína HBx do HBV ao desenvolvimento do HCC. A maioria dos estudos sobre a função da proteína HBx sugere que ela é uma proteína reguladora de funções pleiotrópicas com a capacidade de induzir o crescimento tumoral. Isso é possivelmente devido à sua capacidade de interagir com uma vasta gama de proteínas celulares. No presente estudo investigamos os aspectos moleculares da estrutura e função da proteína HBx e os resultados foram contextualizados no processo de transformação celular. Observamos pela primeira vez a capacidade da proteína HBx em se ligar ao RNA contendo seqüências ricas em adenina e uracila (AU), que são presentes em alguns proto-oncogenes como c-myc e c-fos. A geração de proteínas truncadas permitiu mapear a região de interação entre HBx e RNA. Realizamos ensaios de mutação sítio-dirigida em HBx e substituímos todas as cisteínas por serinas. Nossos resultados sugerem que as cisteínas na proteína HBx são de menor importância para a sua interação com o RNA e com as proteínas humanas p53 e RXR. Descobrimos ainda uma nova proteína humana que interage com HBx: E4F. Este fator de transcrição humano está relacionado com o controle do ciclo celular, com a segregação cromossômica e com a embriogênese. Ensaios em leveduras e in vitro mostraram que HBx selvagem, bem como as suas formas mutadas, foram capazes de interagir e regular a função de E4F, indicando um possível novo mecanismo para a transformação celular e a regulação da transcrição viral, uma vez que E4F exibiu uma capacidade de interagir com a região ¿enhancer II¿ do genoma do HBVAbstract: Viral hepatitis is an important global public health problem. Epidemiological data show that worldwide 350 million people are chronically infected with the hepatitis B virus. About 95% of the infections cure spontaneously, but the chronically infected patients may develop liver cirrhosis or even hepatocellular carcinoma (HCC). A large body of evidence points to the viral onco-protein HBx as the principal cause for the cellular transformation. The majority of studies on HBx function suggest that it is a regulatory protein with pleiotropic functions and its capacity to induce tumor growth may be due to its ability to interact with a diverse array of cellular proteins. In the present study we investigated molecular and structural aspects of the function of the HBx protein in order to be able to shed light on the process of cellular transformation. We were able to demonstrate that HBx protein has the ability to bind to an AU-rich RNA sequences present in the mRNAs of certain proto-oncogenes such as c-myc and c-fos. The generation of truncated proteins allowed to map the region of interaction of HBx with the RNA. Furthermore, we performed site directed mutagenesis studies of HBx protein and substituted all of its cysteine residues with serines. Our data suggest that the cysteine residues in the HBx protein are of minor importance for its interaction with RNA, p53 and RXR proteins. Finally, we discovered in E4F a new human interacting protein partner for the HBx protein. The transcription factor E4F has been functionally implicated in the control of the cell cycle, the chromosomal segregation and embriogenesis. In studies using the yeast we further showed that wild-type HBx, as well as its mutated forms, can physically interact with the E4F protein and regulate its function. This indicates a possible new mechanism of cellular transformation and the regulation of the viral transcription, since the human protein E4F demonstrated the capacity to bind to the enhancer II region of the HBV genomeDoutoradoBioquimicaDoutor em Biologia Funcional e Molecula

Nitrogen fertilization management and nitrogen (15N) utilization by corn crop in Red Latosol

O N é o nutriente absorvido em maior quantidade pelo milho, o que mais influencia a produtividade de grãos e o de manejo mais complexo. O objetivo deste trabalho foi avaliar o efeito de doses e parcelamentos de N, na forma de uréia 15N, sobre a produtividade de grãos, o aproveitamento do N do fertilizante e a quantidade de N nativo do solo absorvida pelo milho em um Latossolo Vermelho. O delineamento experimental foi o de blocos casualizados com nove tratamentos e quatro repetições, compreendido de cinco doses de N: 0, 55, 95, 135 e 175 kg ha-1 de N, aplicando-se 15 kg na semeadura e o restante em diferentes estratégias de parcelamentos: 40 e 80 kg ha-1 no estádio de oito folhas ou ½ no estádio de quatro folhas + ½ no estádio de oito folhas; 120 kg ha-1 fracionados em ½ + ½ ou ¹/3 + ¹/3 + ¹/3 no estádio de quatro, oito ou 12 folhas; e 160 kg ha-1 parcelados em ¼ + ³/8 + ³/8 ou ¼ + ¼ + ¼ + ¼ no estádio de quatro, oito, 12 folhas ou de florescimento e polinização. O aproveitamento do N do fertilizante pelo milho foi, em média, de 39 % e o solo foi a principal fonte do nutriente para a cultura. A aplicação de 135 kg ha-1 de N parcelados em três vezes, até o estádio de oito folhas, proporcionou maior aproveitamento do N do fertilizante (52 %) e maior produtividade de grãos.Nitrogen is the nutrient that is most absorbed by corn crop, influences grain yield most, and requires the most complex management. The objective of this work was to evaluate the effect of nitrogen (urea 15N) rate and split-applications, on grain yield, N fertilizer utilization and amount of soil native N absorbed by corn crop in a Red Latosol. The experiment was arranged in a randomized complete block design, with nine treatments and four replications, represented by five N rates: 0, 55, 95, 135 and 175 kg ha-1 N, 15 kg of N applied at sowing, and the remaining amount in different split-applications: 40 and 80 kg ha-1 applied in single rates in the 8-leaf stage or half in the 4-leaf stage + half in the 8-leaf stage; 120 kg ha-1 split in 1/2 + 1/2 or 1/3 + 1/3 + 1/3 in the 4, 8 or 12-leaf stage; 160 kg ha-1 split in 1/4 + 3/8 + 3/8 or 1/4 + 1/4 + 1/4 + 1/4 in the 4, 8, 12-leaf stages or at flowering and pollination. The N fertilizer use by corn was, on average, 39 %, and the soil was the main source of the nutrient for the crop. With three split applications of 135 kg ha-1 N, until 8 leaves, the N fertilizer use is most efficient (52 %) and the grain yield highest.International Atomic Energy Agenc

Measurement of the top quark forward-backward production asymmetry and the anomalous chromoelectric and chromomagnetic moments in pp collisions at √s = 13 TeV

Abstract The parton-level top quark (t) forward-backward asymmetry and the anomalous chromoelectric (d̂ t) and chromomagnetic (μ̂ t) moments have been measured using LHC pp collisions at a center-of-mass energy of 13 TeV, collected in the CMS detector in a data sample corresponding to an integrated luminosity of 35.9 fb−1. The linearized variable AFB(1) is used to approximate the asymmetry. Candidate t t ¯ events decaying to a muon or electron and jets in final states with low and high Lorentz boosts are selected and reconstructed using a fit of the kinematic distributions of the decay products to those expected for t t ¯ final states. The values found for the parameters are AFB(1)=0.048−0.087+0.095(stat)−0.029+0.020(syst),μ̂t=−0.024−0.009+0.013(stat)−0.011+0.016(syst), and a limit is placed on the magnitude of | d̂ t| < 0.03 at 95% confidence level. [Figure not available: see fulltext.

Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

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An embedding technique to determine ττ backgrounds in proton-proton collision data

An embedding technique is presented to estimate standard model tau tau backgrounds from data with minimal simulation input. In the data, the muons are removed from reconstructed mu mu events and replaced with simulated tau leptons with the same kinematic properties. In this way, a set of hybrid events is obtained that does not rely on simulation except for the decay of the tau leptons. The challenges in describing the underlying event or the production of associated jets in the simulation are avoided. The technique described in this paper was developed for CMS. Its validation and the inherent uncertainties are also discussed. The demonstration of the performance of the technique is based on a sample of proton-proton collisions collected by CMS in 2017 at root s = 13 TeV corresponding to an integrated luminosity of 41.5 fb(-1).Peer reviewe

MUSiC : a model-unspecific search for new physics in proton-proton collisions at root s=13TeV

Results of the Model Unspecific Search in CMS (MUSiC), using proton-proton collision data recorded at the LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1), are presented. The MUSiC analysis searches for anomalies that could be signatures of physics beyond the standard model. The analysis is based on the comparison of observed data with the standard model prediction, as determined from simulation, in several hundred final states and multiple kinematic distributions. Events containing at least one electron or muon are classified based on their final state topology, and an automated search algorithm surveys the observed data for deviations from the prediction. The sensitivity of the search is validated using multiple methods. No significant deviations from the predictions have been observed. For a wide range of final state topologies, agreement is found between the data and the standard model simulation. This analysis complements dedicated search analyses by significantly expanding the range of final states covered using a model independent approach with the largest data set to date to probe phase space regions beyond the reach of previous general searches.Peer reviewe

Measurement of prompt open-charm production cross sections in proton-proton collisions at root s=13 TeV

The production cross sections for prompt open-charm mesons in proton-proton collisions at a center-of-mass energy of 13TeV are reported. The measurement is performed using a data sample collected by the CMS experiment corresponding to an integrated luminosity of 29 nb(-1). The differential production cross sections of the D*(+/-), D-+/-, and D-0 ((D) over bar (0)) mesons are presented in ranges of transverse momentum and pseudorapidity 4 < p(T) < 100 GeV and vertical bar eta vertical bar < 2.1, respectively. The results are compared to several theoretical calculations and to previous measurements.Peer reviewe

Search for Physics beyond the Standard Model in Events with Overlapping Photons and Jets

Results are reported from a search for new particles that decay into a photon and two gluons, in events with jets. Novel jet substructure techniques are developed that allow photons to be identified in an environment densely populated with hadrons. The analyzed proton-proton collision data were collected by the CMS experiment at the LHC, in 2016 at root s = 13 TeV, and correspond to an integrated luminosity of 35.9 fb(-1). The spectra of total transverse hadronic energy of candidate events are examined for deviations from the standard model predictions. No statistically significant excess is observed over the expected background. The first cross section limits on new physics processes resulting in such events are set. The results are interpreted as upper limits on the rate of gluino pair production, utilizing a simplified stealth supersymmetry model. The excluded gluino masses extend up to 1.7 TeV, for a neutralino mass of 200 GeV and exceed previous mass constraints set by analyses targeting events with isolated photons.Peer reviewe

Measurement of nuclear modification factors of gamma(1S)), gamma(2S), and gamma(3S) mesons in PbPb collisions at root s(NN)=5.02 TeV

The cross sections for ϒ(1S), ϒ(2S), and ϒ(3S) production in lead-lead (PbPb) and proton-proton (pp) collisions at √sNN = 5.02 TeV have been measured using the CMS detector at the LHC. The nuclear modification factors, RAA, derived from the PbPb-to-pp ratio of yields for each state, are studied as functions of meson rapidity and transverse momentum, as well as PbPb collision centrality. The yields of all three states are found to be significantly suppressed, and compatible with a sequential ordering of the suppression, RAA(ϒ(1S)) > RAA(ϒ(2S)) > RAA(ϒ(3S)). The suppression of ϒ(1S) is larger than that seen at √sNN = 2.76 TeV, although the two are compatible within uncertainties. The upper limit on the RAA of ϒ(3S) integrated over pT, rapidity and centrality is 0.096 at 95% confidence level, which is the strongest suppression observed for a quarkonium state in heavy ion collisions to date. © 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3.Peer reviewe