Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 34
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Nucleic Acids Res ; 2024 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-39225047

RESUMO

RNA binding proteins drive proliferation and tumorigenesis by regulating the translation and stability of specific subsets of messenger RNAs (mRNAs). We have investigated the role of eukaryotic initiation factor 4B (eIF4B) in this process and identify 10-fold more RNA binding sites for eIF4B in tumour cells from patients with diffuse large B-cell lymphoma compared to control B cells and, using individual-nucleotide resolution UV cross-linking and immunoprecipitation, find that eIF4B binds the entire length of mRNA transcripts. eIF4B stimulates the helicase activity of eIF4A, thereby promoting the unwinding of RNA structure within the 5' untranslated regions of mRNAs. We have found that, in addition to its well-documented role in mRNA translation, eIF4B additionally interacts with proteins associated with RNA turnover, including UPF1 (up-frameshift protein 1), which plays a key role in histone mRNA degradation at the end of S phase. Consistent with these data, we locate an eIF4B binding site upstream of the stem-loop structure in histone mRNAs and show that decreased eIF4B expression alters histone mRNA turnover and delays cell cycle progression through S phase. Collectively, these data provide insight into how eIF4B promotes tumorigenesis.

2.
EMBO Rep ; 21(3): e46734, 2020 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-32017402

RESUMO

The mechanisms that regulate the switch between epidermal progenitor state and differentiation are not fully understood. Recent findings indicate that the chromatin remodelling BAF complex (Brg1-associated factor complex or SWI/SNF complex) and the transcription factor p63 mutually recruit one another to open chromatin during epidermal differentiation. Here, we identify a long non-coding transcript that includes an ultraconserved element, uc.291, which physically interacts with ACTL6A and modulates chromatin remodelling to allow differentiation. Loss of uc.291 expression, both in primary keratinocytes and in three-dimensional skin equivalents, inhibits differentiation as indicated by epidermal differentiation complex genes down-regulation. ChIP experiments reveal that upon uc.291 depletion, ACTL6A is bound to the differentiation gene promoters and inhibits BAF complex targeting to induce terminal differentiation genes. In the presence of uc.291, the ACTL6A inhibitory effect is released, allowing chromatin changes to promote the expression of differentiation genes. Thus, uc.291 interacts with ACTL6A to modulate chromatin remodelling activity, allowing the transcription of late differentiation genes.


Assuntos
Actinas/genética , Proteínas Cromossômicas não Histona/genética , Proteínas de Ligação a DNA/genética , RNA Longo não Codificante , Células Cultivadas , Cromatina/genética , Montagem e Desmontagem da Cromatina , Proteínas Cromossômicas não Histona/metabolismo , Humanos , RNA Longo não Codificante/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
3.
Int J Mol Sci ; 23(5)2022 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-35269953

RESUMO

The advance of experimental and computational techniques has allowed us to highlight the existence of numerous different mechanisms of RNA maturation, which have been so far unknown. Besides canonical splicing, consisting of the removal of introns from pre-mRNA molecules, non-canonical splicing events may occur to further increase the regulatory and coding potential of the human genome. Among these, splicing of microexons, recursive splicing and biogenesis of circular and chimeric RNAs through back-splicing and trans-splicing processes, respectively, all contribute to expanding the repertoire of RNA transcripts with newly acquired regulatory functions. Interestingly, these non-canonical splicing events seem to occur more frequently in the central nervous system, affecting neuronal development and differentiation programs with important implications on brain physiology. Coherently, dysregulation of non-canonical RNA processing events is associated with brain disorders, including brain tumours. Herein, we summarize the current knowledge on molecular and regulatory mechanisms underlying canonical and non-canonical splicing events with particular emphasis on cis-acting elements and trans-acting factors that all together orchestrate splicing catalysis reactions and decisions. Lastly, we review the impact of non-canonical splicing on brain physiology and pathology and how unconventional splicing mechanisms may be targeted or exploited for novel therapeutic strategies in cancer.


Assuntos
Neoplasias , Splicing de RNA , Processamento Alternativo/genética , Encéfalo/metabolismo , Humanos , Íntrons , Neoplasias/genética , RNA/genética , Precursores de RNA/genética , Splicing de RNA/genética
4.
Proc Natl Acad Sci U S A ; 115(24): 6219-6224, 2018 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-29844156

RESUMO

TAp73 is a transcription factor that plays key roles in brain development, aging, and cancer. At the cellular level, TAp73 is a critical homeostasis-maintaining factor, particularly following oxidative stress. Although major studies focused on TAp73 transcriptional activities have indicated a contribution of TAp73 to cellular metabolism, the mechanisms underlying its role in redox homeostasis have not been completely elucidated. Here we show that TAp73 contributes to the oxidative stress response by participating in the control of protein synthesis. Regulation of mRNA translation occupies a central position in cellular homeostasis during the stress response, often by reducing global rates of protein synthesis and promoting translation of specific mRNAs. TAp73 depletion results in aberrant ribosomal RNA (rRNA) processing and impaired protein synthesis. In particular, polysomal profiles show that TAp73 promotes the integration of mRNAs that encode rRNA-processing factors in polysomes, supporting their translation. Concurrently, TAp73 depletion causes increased sensitivity to oxidative stress that correlates with reduced ATP levels, hyperactivation of AMPK, and translational defects. TAp73 is important for maintaining active translation of mitochondrial transcripts in response to oxidative stress, thus promoting mitochondrial activity. Our results indicate that TAp73 contributes to redox homeostasis by affecting the translational machinery, facilitating the translation of specific mitochondrial transcripts. This study identifies a mechanism by which TAp73 contributes to the oxidative stress response and describes a completely unexpected role for TAp73 in regulating protein synthesis.


Assuntos
Estresse Oxidativo/genética , Biossíntese de Proteínas/genética , Proteína Tumoral p73/genética , Proteína Tumoral p73/metabolismo , Células A549 , Células HEK293 , Humanos , Mitocôndrias/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/metabolismo
5.
Proc Natl Acad Sci U S A ; 115(46): E10869-E10878, 2018 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-30381462

RESUMO

Mutations in the TP53 gene and microenvironmentally driven activation of hypoxia-inducible factor-1 (HIF-1) typically occur in later stages of tumorigenesis. An ongoing challenge is the identification of molecular determinants of advanced cancer pathogenesis to design alternative last-line therapeutic options. Here, we report that p53 mutants influence the tumor microenvironment by cooperating with HIF-1 to promote cancer progression. We demonstrate that in non-small cell lung cancer (NSCLC), p53 mutants exert a gain-of-function (GOF) effect on HIF-1, thus regulating a selective gene expression signature involved in protumorigenic functions. Hypoxia-mediated activation of HIF-1 leads to the formation of a p53 mutant/HIF-1 complex that physically binds the SWI/SNF chromatin remodeling complex, promoting expression of a selective subset of hypoxia-responsive genes. Depletion of p53 mutants impairs the HIF-mediated up-regulation of extracellular matrix (ECM) components, including type VIIa1 collagen and laminin-γ2, thus affecting tumorigenic potential of NSCLC cells in vitro and in mouse models in vivo. Analysis of surgically resected human NSCLC revealed that expression of this ECM gene signature was highly correlated with hypoxic tumors exclusively in patients carrying p53 mutations and was associated with poor prognosis. Our data reveal a GOF effect of p53 mutants in hypoxic tumors and suggest synergistic activities of p53 and HIF-1. These findings have important implications for cancer progression and might provide innovative last-line treatment options for advanced NSCLC.


Assuntos
Carcinoma Pulmonar de Células não Pequenas/genética , Fator 1 Induzível por Hipóxia/genética , Neoplasias Pulmonares/genética , Proteína Supressora de Tumor p53/metabolismo , Animais , Carcinoma Pulmonar de Células não Pequenas/metabolismo , Carcinoma Pulmonar de Células não Pequenas/patologia , Hipóxia Celular/genética , Linhagem Celular Tumoral , Matriz Extracelular , Genes p53 , Xenoenxertos , Humanos , Fator 1 Induzível por Hipóxia/metabolismo , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/patologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Mutação , Ativação Transcricional , Microambiente Tumoral , Proteína Supressora de Tumor p53/genética
6.
Chemphyschem ; 15(7): 1336-44, 2014 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-24470302

RESUMO

We present a computational investigation of the nematic phase of the bent-core liquid crystal A131. We use an integrated approach that bridges density functional theory calculations of molecular geometry and torsional potentials to elastic properties through the molecular conformational and orientational distribution function. This unique capability to simultaneously access different length scales enables us to consistently describe molecular and material properties. We can reassign (13)C NMR chemical shifts and analyze the dependence of phase properties on molecular shape. Focusing on the elastic constants we can draw some general conclusions on the unconventional behavior of bent-core nematics and highlight the crucial role of a properly-bent shape.

7.
J Exp Clin Cancer Res ; 42(1): 214, 2023 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-37599362

RESUMO

BACKGROUND: Medulloblastoma (MB) is the most common cerebellar malignancy during childhood. Among MB, MYC-amplified Group 3 tumors display the worst prognosis. MYC is an oncogenic transcription factor currently thought to be undruggable. Nevertheless, targeting MYC-dependent processes (i.e. transcription and RNA processing regulation) represents a promising approach. METHODS: We have tested the sensitivity of MYC-driven Group 3 MB cells to a pool of transcription and splicing inhibitors that display a wide spectrum of targets. Among them, we focus on THZ531, an inhibitor of the transcriptional cyclin-dependent kinases (CDK) 12 and 13. High-throughput RNA-sequencing analyses followed by bioinformatics and functional analyses were carried out to elucidate the molecular mechanism(s) underlying the susceptibility of Group 3 MB to CDK12/13 chemical inhibition. Data from International Cancer Genome Consortium (ICGC) and other public databases were mined to evaluate the functional relevance of the cellular pathway/s affected by the treatment with THZ531 in Group 3 MB patients. RESULTS: We found that pharmacological inhibition of CDK12/13 is highly selective for MYC-high Group 3 MB cells with respect to MYC-low MB cells. We identified a subset of genes enriched in functional terms related to the DNA damage response (DDR) that are up-regulated in Group 3 MB and repressed by CDK12/13 inhibition. Accordingly, MYC- and CDK12/13-dependent higher expression of DDR genes in Group 3 MB cells limits the toxic effects of endogenous DNA lesions in these cells. More importantly, chemical inhibition of CDK12/13 impaired the DDR and induced irreparable DNA damage exclusively in MYC-high Group 3 MB cells. The augmented sensitivity of MYC-high MB cells to CDK12/13 inhibition relies on the higher elongation rate of the RNA polymerase II in DDR genes. Lastly, combined treatments with THZ531 and DNA damage-inducing agents synergically suppressed viability of MYC-high Group 3 MB cells. CONCLUSIONS: Our study demonstrates that CDK12/13 activity represents an exploitable vulnerability in MYC-high Group 3 MB and may pave the ground for new therapeutic approaches for this high-risk brain tumor.


Assuntos
Neoplasias Cerebelares , Meduloblastoma , Humanos , Meduloblastoma/tratamento farmacológico , Meduloblastoma/genética , Regulação para Cima , Anilidas , Neoplasias Cerebelares/tratamento farmacológico , Neoplasias Cerebelares/genética , Proteína Quinase CDC2 , Quinases Ciclina-Dependentes/genética
8.
Chemphyschem ; 13(17): 3958-65, 2012 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-23001812

RESUMO

An azobenzene derivative, namely diheptylazobenzene, showing the nematic and smectic A liquid crystalline phases, was investigated by means of a combined approach based on NMR and DFT calculations. (14)N NMR quadrupole- and chemical-shift-perturbed spectra were acquired in the whole mesophasic range, providing both experimental quadrupolar splittings and chemical shift anisotropy values. On the same mesogen, deuterium labelled at the α-position of the hydrocarbon chain, (2)H NMR quadrupole-perturbed spectra were recorded. The analysis of these NMR data was performed with the help of ab initio calculations, in vacuo and by taking into account the effect of the anisotropic environment typical of liquid crystals, by using the IEF-PCM model. The geometry optimizations of the azomesogen in the trans and cis configurations were performed by DFT calculations employing the combination of B3LYP functional with the 6-311G(d) basis set. The analysis of experimental NMR data was performed by considering the trans configuration as the most populated one and the corresponding quadrupolar tensors and chemical shielding tensors were determined at the DFT level of theory. The main result of this work is the determination of a relatively high and temperature-dependent molecular biaxiality of the trans state of this azomesogen.

9.
Phys Chem Chem Phys ; 13(27): 12595-602, 2011 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-21660321

RESUMO

A Density Functional Theory (DFT) study of the absorbance and fluorescence emission characteristics of the cyanine thiazole orange (TO) in solution and when intercalated in DNA was carried out in combination with spectrophotometric and spectrofluorometric experiments under different conditions (temperature, concentration, solvent viscosity). T-jump relaxation kinetics of the TO monomer-dimer conversion enabled the thermodynamic parameters of this process to be evaluated. The overall data collected provided information on the features of the "light-switch" by the fluorescent TO and the comparison between experimental and calculated photo-physical properties allowed us to explain and rationalize both shifts and quenching/enhancing effects on fluorescence due to solvation, dimerisation and intercalation in the DNA.


Assuntos
Benzotiazóis/química , Quinolinas/química , DNA/química , Substâncias Intercalantes/química , Luz , Teoria Quântica , Soluções/química , Espectrometria de Fluorescência
10.
J Phys Chem A ; 115(35): 10035-44, 2011 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-21797250

RESUMO

In this study we combined QM calculations and NMR measurements to understand at a detailed level the complex interplay of structural/electronic properties with the effects of the solvent in the NLO activity of push-pull systems, quantified in terms of variations of the static hyperpolarizability. Different parameters (bond lengths and bond length alternation, vibrational frequencies, electronic charge distribution) are introduced and tested to rationalize both the solvent sensitivity of three molecular systems (namely, p-nitroaniline, ethyl 4-ammino benzoate, and 5-nitro-1H-indole) and the differences among them. This analysis has finally allowed us to establish a clear correlation between the charge transfer behavior of the systems, their NLO properties, and NMR parameters also validating simplified but effective chemical analyses based on resonance limit forms.

11.
Nat Commun ; 12(1): 4920, 2021 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-34389715

RESUMO

Malignant mesothelioma (MpM) is an aggressive, invariably fatal tumour that is causally linked with asbestos exposure. The disease primarily results from loss of tumour suppressor gene function and there are no 'druggable' driver oncogenes associated with MpM. To identify opportunities for management of this disease we have carried out polysome profiling to define the MpM translatome. We show that in MpM there is a selective increase in the translation of mRNAs encoding proteins required for ribosome assembly and mitochondrial biogenesis. This results in an enhanced rate of mRNA translation, abnormal mitochondrial morphology and oxygen consumption, and a reprogramming of metabolic outputs. These alterations delimit the cellular capacity for protein biosynthesis, accelerate growth and drive disease progression. Importantly, we show that inhibition of mRNA translation, particularly through combined pharmacological targeting of mTORC1 and 2, reverses these changes and inhibits malignant cell growth in vitro and in ex-vivo tumour tissue from patients with end-stage disease. Critically, we show that these pharmacological interventions prolong survival in animal models of asbestos-induced mesothelioma, providing the basis for a targeted, viable therapeutic option for patients with this incurable disease.


Assuntos
Mesotelioma Maligno/genética , Oncogenes/genética , Biossíntese de Proteínas/genética , RNA Mensageiro/genética , Animais , Amianto , Humanos , Alvo Mecanístico do Complexo 1 de Rapamicina/antagonistas & inibidores , Alvo Mecanístico do Complexo 1 de Rapamicina/metabolismo , Alvo Mecanístico do Complexo 2 de Rapamicina/antagonistas & inibidores , Alvo Mecanístico do Complexo 2 de Rapamicina/metabolismo , Mesotelioma Maligno/induzido quimicamente , Mesotelioma Maligno/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mitocôndrias/genética , Mitocôndrias/metabolismo , Naftiridinas/farmacologia , Polirribossomos/efeitos dos fármacos , Polirribossomos/metabolismo , Biossíntese de Proteínas/efeitos dos fármacos , RNA Mensageiro/metabolismo , Células Tumorais Cultivadas
12.
Langmuir ; 26(22): 16762-70, 2010 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-20883045

RESUMO

The aggregation of perfluoroctanoate salts in H(2)O is studied by (19)F NMR on solutions of LiPFO, NaPFO, and CsPFO, without and with the addition of two poly(ethylene glycol) (PEG) oligomers of molecular weight 1500 and 3400 Da, respectively, and with the addition of suitable crown ethers. The (19)F chemical shift (cs) trends are monitored, at 25 °C, in a concentration range including the critical micellar concentration (cmc) or, in the presence of PEG, the critical aggregation concentration (cac). The cac values in the samples with PEG are lower than the cmc values of the corresponding samples without PEG; moreover, the (19)F cs trends above the cac and above the polymer saturation concentration reveal and help to explain some peculiarities of the aggregation process of PEG on PFO micelles, which, in the first step, seems to occur while the surfactant concentration in water is still increasing. Also in LiPFO/H(2)O or NaPFO/H(2)O solutions containing 12-crown-4 or 15-crown-5 ethers, suitable to complex Li(+) or Na(+) ions, respectively, the cmc decreases. On the other hand, the micellization process in the presence of crown ethers does not show other peculiarities. The prevailing conformations of the PFO chain are discussed on the basis of quantum-mechanical calculations. The theoretical chemical shifts were computed at the DFT level of theory, taking into account the effects of the environment by means of the IEF-PCM method. The helical structure is the most stable one, but anti conformations are easily accessible, in both the aqueous and fluorinated environment. The comparison between computed and experimental chemical shifts indicates that anti conformations are more important in the micelles than in water and in CsPFO micelles than in LiPFO or NaPFO ones.

13.
Phys Chem Chem Phys ; 12(31): 8999-9010, 2010 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-20532298

RESUMO

With this study we show that the maturity reached by quantum-mechanical (QM) modeling has allowed a new analytical approach to the design of molecular probes. In this approach, the strategy is to integrate suited computational tools with multi-spectroscopic measurements to identify specific signals for the characterization of the molecular probe with respect to the perturbation used and the environmental conditions applied. The application of the strategy to a typical optical probe (2-acetylanthracene) has allowed the identification of specific IR and NMR signals for the characterization of the conformational states in both solid and solution states. This analysis has been successively extended to the investigation of specific optical signals. In particular we have shown that the introduction of a substituent in specific positions of the aromatic structure induces a different perturbation in the different excited states of the precursor anthracene with consequent differentiations of the states with respect to their solvent sensitivity (both in terms of bulk and specific effects). Finally, the integration of simulated and experimental emission spectra has revealed a possible isomerization in the excited state with resulting change of the conformational state in the absorbing and the emitting species.


Assuntos
Sondas Moleculares/química , Antracenos/química , Espectroscopia de Ressonância Magnética , Teoria Quântica , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta
14.
J Phys Chem A ; 114(12): 4375-87, 2010 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-20187622

RESUMO

Cardiolipin is a key lipid component in many biological membranes. Proton conduction and proton-lipid interactions on the membrane surface are thought to be central to mitochondrial energy production. However, details on the cardiolipin headgroup structure are lacking and the protonation state of this lipid at physiological pH is not fully established. Here we present ab initio DFT calculations of the cardiolipin (CL) headgroup and its 2'-deoxy derivative (dCL), with the aim of establishing a connection between structure and acid-base equilibrium in CL. Furthermore, we investigate the effects of solvation on the molecular conformations. In our model, both CL and dCL showed a significant gap between the two pK(a) values, with pK(a2) above the physiological range, and intramolecular hydrogen bonds were found to play a central role in the conformations of both molecules. This behavior was also observed experimentally in CL. Structures derived from the DFT calculations were compared with those obtained experimentally, collected for CL in the Protein Data Bank, and conformations from previous as well as new molecular dynamics simulations of cardiolipin bilayers. Transition states for proton transfer in CL were investigated, and we estimate that protons can exchange between phosphate groups with an approximate 4-5 kcal/mol barrier. Computed NMR and IR spectral properties were found to be in reasonable agreement with experimental results available in the literature.


Assuntos
Cardiolipinas/química , Modelos Químicos , Teoria Quântica , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Simulação de Dinâmica Molecular , Fosfatos/química , Prótons , Espectrofotometria Infravermelho , Termodinâmica
15.
Oncogene ; 39(4): 754-766, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31570788

RESUMO

Efficient repair of DNA double-strand breaks (DSBs) is of critical importance for cell survival. Although non-homologous end joining (NHEJ) is the most used DSBs repair pathway in the cells, how NHEJ factors are sequentially recruited to damaged chromatin remains unclear. Here, we identify a novel role for the zinc-finger protein ZNF281 in participating in the ordered recruitment of the NHEJ repair factor XRCC4 at damage sites. ZNF281 is recruited to DNA lesions within seconds after DNA damage through a mechanism dependent on its DNA binding domain and, at least in part, on poly-ADP ribose polymerase (PARP) activity. ZNF281 binds XRCC4 through its zinc-finger domain and facilitates its recruitment to damaged sites. Consequently, depletion of ZNF281 impairs the efficiency of the NHEJ repair pathway and decreases cell viability upon DNA damage. Survival analyses from datasets of commonly occurring human cancers show that higher levels of ZNF281 correlate with poor prognosis of patients treated with DNA-damaging therapies. Thus, our results define a late ZNF281-dependent regulatory step of NHEJ complex assembly at DNA lesions and suggest additional possibilities for cancer patients' stratification and for the development of personalised therapeutic strategies.


Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA por Junção de Extremidades , Neoplasias/genética , Neoplasias/patologia , Proteínas Repressoras/metabolismo , Sistemas CRISPR-Cas , Linhagem Celular Tumoral , Proteínas de Ligação a DNA/metabolismo , Bases de Dados Genéticas , Humanos , Neoplasias/metabolismo , Poli(ADP-Ribose) Polimerase-1/genética , Poli(ADP-Ribose) Polimerase-1/metabolismo , Prognóstico , Proteínas Repressoras/genética , Taxa de Sobrevida
16.
Chemphyschem ; 10(15): 2679-91, 2009 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-19728341

RESUMO

The molecular dynamics of a ferroelectric liquid crystal, denoted ZLL 7/*, is investigated by means of (2)H NMR relaxation. The spin-lattice (T(1Q) and T(1Z)) and spin-spin (T(2)) relaxation times of two isotopomers of ZLL 7/*, labeled on the phenyl and biphenyl fragments, are measured and their behavior upon passing from the SmA to the hexatic phase, through the ferroelectric SmC*, antiferroelectric SmC*(A), and re-entrant ferroelectric SmC*(re) phases, is discussed. A comparison between the measured T(2) and T(2)*, directly related to the experimental linewidth, provides information on the heterogeneity of the system, thus allowing confirmation of previous hypotheses concerning the structural and ordering properties of the SmC*(A) and SmC*(re) phases. The possibility to look at different sites of the core of the ZLL 7/* smectogen reveals a peculiar sensitivity of the phenyl moiety with respect to the biphenyl fragment, which may be justified by its vicinity to the chiral centers. Interestingly, the trend of the longitudinal relaxation times is characterized by a minimum that corresponds to the SmC*(A) and SmC*(re) phases, which is reproducible for the two isotopomers and at several Larmor frequencies. A quantitative analysis of T(1Q) and T(1Z) is performed in the SmA and SmC* phases, for which the narrowing regime approximation is valid. A multifrequency approach is applied to self-consistently determine the diffusion coefficients for the overall molecular motions, namely spinning and tumbling, and the internal rotations around the para axes of the phenyl and biphenyl fragments. The effect of the magnetic field in unwinding the helical structure of the SmC* phase (for H>9 T) allows observation of a sensitive change in the rotational diffusion coefficients in the frustrated unwound SmC* phase with respect to the SmC* phase.

17.
Chemphyschem ; 8(18): 2575-87, 2007 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-18067200

RESUMO

We present a theoretical and experimental (2)H NMR study of the effect of external magnetic fields on the supramolecular organization of chiral smectic liquid-crystalline mesophases, such as SmC* and re-entrant SmC*. Three experimental cases in which the supramolecular helical structure of the smectic C* phase is unwound by a magnetic field (H), parallel to the helical axes of this phase, are discussed in detail. Unwinding of the helical structure is described by using a theoretical model based on the Landau-de Gennes theory, which allows us to explain the transition temperatures among the SmA, SmC*, and uSmC* phases. The energy-density behavior in the vicinity of the transitions and the value of the critical magnetic field H(C) for unwinding the helical structure are discussed by applying this model to three ferroelectric smectogens (MBHB, 11EB1M7, ZLL7/*), which are studied by (2)H NMR spectroscopy at different magnetic fields (from 2.4 to 9.4 Tesla). Furthermore, the tilt angle of the three smectogens in the SmC* phase has been directly evaluated, for the first time, by comparing the quadrupolar splittings at different magnetic fields. In one case, (2)H NMR angular measurements are used to obtain the tilt angle in the re-entrant smectic C phase.


Assuntos
Carbono/química , Físico-Química/métodos , Espectroscopia de Ressonância Magnética/métodos , Magnetismo , Campos Eletromagnéticos , Imageamento por Ressonância Magnética , Modelos Químicos , Modelos Moleculares , Modelos Teóricos , Conformação Molecular , Transição de Fase , Temperatura
18.
Oncotarget ; 8(22): 35669-35680, 2017 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-27447964

RESUMO

Transcribed-ultraconserved regions (T-UCRs) are long non-coding RNAs (lncRNA) encoded by a subset of long ultraconserved stretches in the human genome. Recent studies revealed that the expression of several T-UCRs is altered in cancer and growing evidences underline the importance of T-UCRs in oncogenesis, offering also potential new strategies for diagnosis and prognosis. We found that overexpression of one specific T-UCRs named uc.63 is associated with bad outcome in luminal A subtype of breast cancer patients. uc.63 is localized in the third intron of exportin-1 gene (XPO1) and is transcribed in the same orientation of its host gene. Interestingly, silencing of uc.63 induces apoptosis in vitro. However, silencing of host gene XPO1 does not cause the same effect suggesting that the transcription of uc.63 is independent of XPO1. Our results reveal an important role of uc.63 in promoting breast cancer cells survival and offer the prospect to identify a signature associated with poor prognosis.


Assuntos
Neoplasias da Mama/genética , RNA Longo não Codificante/genética , Neoplasias da Mama/mortalidade , Linhagem Celular Tumoral , Biologia Computacional/métodos , Sequência Conservada , Feminino , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Humanos , Carioferinas/genética , Prognóstico , RNA Mensageiro/genética , Receptores Citoplasmáticos e Nucleares/genética , Transcrição Gênica , Proteína Exportina 1
19.
J Phys Chem B ; 110(33): 16459-70, 2006 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-16913777

RESUMO

In this work, two selectively deuterium-labeled isotopomers of the (S)-2-methylbutyl- [4'-(4' '-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')-benzoyl)-propionyl)]-propionate (ZLL 7/), one labeled on the phenyl ring (ZLL 7/-phe-D2) and the other one on the biphenyl fragment (ZLL 7/-biphe-D2), have been investigated by deuterium NMR (DNMR) spectroscopy and other experimental techniques. These compounds possess the paraelectric SmA, the ferroelectric SmC, the antiferroelectric SmC(A), the re-entrant ferroelectric SmC(re), and the ferroelectric hexatic phases down to room temperature. The orientational ordering properties of the two labeled fragments have been determined by means of DNMR, and the mesophase behavior at two magnetic fields is discussed. In particular, the effect of the magnetic field on the supramolecular structure of the SmC and SmC(re) phases is commented. This study revealed to be useful to understand the structural and conformational properties of the ferroelectric/antiferroelectric/re-entrant/hexatic smectic phases. Mesomorphic properties, spontaneous tilt angle, polarization, and layer spacing have been studied for the labeled materials and compared with those obtained for the nonlabeled compound. The two self-consistent set of data, from optical and DNMR measurements and X-ray results, allow us to associate at the transition from the SmC to the SmC(A) phase a change of the molecular conformation.

20.
Oncotarget ; 7(38): 61890-61904, 2016 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-27542265

RESUMO

Drug resistance of cancer cells is recognized as the primary cause of failure of chemotherapeutic treatment in most human cancers. Growing evidences support the idea that deregulated cellular metabolism is linked to such resistance. Indeed, both components of the glycolytic and mitochondrial pathways are involved in altered metabolism linked to chemoresistance of several cancers. Here we investigated the drug-induced metabolic adaptations able to confer advantages to docetaxel resistant prostate cancer (PCa) cells. We found that docetaxel-resistant PC3 cells (PC3-DR) acquire a pro-invasive behavior undergoing epithelial-to-mesenchymal-transition (EMT) and a decrease of both intracellular ROS and cell growth. Metabolic analyses revealed that PC3-DR cells have a more efficient respiratory phenotype than sensitive cells, involving utilization of glucose, glutamine and lactate by the mitochondrial oxidative phosphorylation (OXPHOS). Consequently, targeting mitochondrial complex I by metformin administration, impairs proliferation and invasiveness of PC3-DR cells without effects on parental cells. Furthermore, stromal fibroblasts, which cause a "reverse Warburg" phenotype in PCa cells, reduce docetaxel toxicity in both sensitive and resistant PCa cells. However, re-expression of miR-205, a microRNA strongly down-regulated in EMT and associated to docetaxel resistance, is able to shift OXPHOS to a Warburg metabolism, thereby resulting in an elevated docetaxel toxicity in PCa cells. Taken together, these findings suggest that resistance to docetaxel induces a shift from Warburg to OXPHOS, mandatory for conferring a survival advantage to resistant cells, suggesting that impairing such metabolic reprogramming could be a successful therapeutic approach.


Assuntos
Antineoplásicos/farmacologia , Resistencia a Medicamentos Antineoplásicos , Fosforilação Oxidativa , Neoplasias da Próstata/tratamento farmacológico , Taxoides/farmacologia , Apoptose , Linhagem Celular Tumoral , Técnicas de Cocultura , Docetaxel , Transição Epitelial-Mesenquimal , Fibroblastos/efeitos dos fármacos , Glucose/metabolismo , Glutamina/metabolismo , Glicólise , Humanos , Masculino , Mitocôndrias/metabolismo , NADP/metabolismo , Fenótipo , Próstata/efeitos dos fármacos , Próstata/metabolismo , Neoplasias da Próstata/metabolismo , Espécies Reativas de Oxigênio/metabolismo
SELEÇÃO DE REFERÊNCIAS
Detalhe da pesquisa