Role of RNA binding protein HuR in antagonizing the microRNA-mediated repression

MicroRNAs (miRNAs) are ~21-nt-long non-coding RNAs regulating gene expression in eukaryotes. In metazoa, miRNAs control gene expression by base-pairing to target mRNAs, bringing about their translational repression and/or deadenylation resulting in mRNA degradation. MiRNA-mediated translational repression is a reversible process in mammalian cells. It was previously demonstrated that target mRNAs containing AU-rich regulatory elements (AREs) in the 3’UTR, can be relieved from miRNA repression in human hepatoma Huh7 or HeLa cells in response to different forms of cellular stress. The derepression required binding of the ELAV family protein HuR to the mRNA 3’UTR (Bhattacharyya et al., Cell 125, 111-1124, 2006). However, whether stress-induced factors other than HuR participate in the process and the actual mechanism of HuR action remain unknown. In the present study, we have addressed these questions, using different cell-based and in vitro assays. Using mutants of HuR accumulating in the cytoplasm in the absence of stress and tumor cell lines constitutively accumulating endogenous HuR in the cytoplasm, we were able to uncouple the HuR effect on miRNA repression from stress. We also found that Ago2 and HuR do not interact with each other and that their binding to target mRNA appears to be largely mutually exclusive. Using an in vitro system with purified miRISC and recombinant HuR and its mutants, we demonstrate that HuR, by oligomerizing along RNA, leads to displacement of miRISC from RNA, even when miRISC is positioned at a distance from the primary HuR-binding site. Further, we show that HuR association with AREs can inhibit RISC-mediated endonucleolytic cleavage of target RNAs both in vivo and in vitro, and also miRNA-mediated deadenylation of RNA in the Krebs-2 ascites extract

Transition metal catalysed Grignard-like allylic activation across tetragonal tin(II) oxide

The reaction of allyl halide and a carbonyl compound under the aegis of tetragonal tin(II) oxide and catalytic d8, d10 metal complexes provides the corresponding homoallylic alcohol, via a novel allyl tin intermediate

HuR protein attenuates miRNA-mediated repression by promoting miRISC dissociation from the target RNA

The microRNA (miRNA)-mediated repression of protein synthesis in mammalian cells is a reversible process. Target mRNAs with regulatory AU-rich elements (AREs) in their 3′-untranslated regions (3′-UTR) can be relieved of miRNA repression under cellular stress in a process involving the embryonic lethal and altered vision family ARE-binding protein HuR. The HuR-mediated derepression occurred even when AREs were positioned at a considerable distance from the miRNA sites raising questions about the mechanism of HuR action. Here, we show that the relief of miRNA-mediated repression involving HuR can be recapitulated in different in vitro systems in the absence of stress, indicating that HuR alone is sufficient to relieve the miRNA repression upon binding to RNA ARE. Using in vitro assays with purified miRISC and recombinant HuR and its mutants, we show that HuR, likely by its property to oligomerize along RNA, leads to the dissociation of miRISC from target RNA even when miRISC and HuR binding sites are positioned at a distance. Further, we demonstrate that HuR association with AREs can also inhibit miRNA-mediated deadenylation of mRNA in the Krebs-2 ascites extract, in a manner likewise depending on the potential of HuR to oligomeriz

HuR protein attenuates miRNA-mediated repression by promoting miRISC dissociation from the target RNA

The microRNA (miRNA)-mediated repression of protein synthesis in mammalian cells is a reversible process. Target mRNAs with regulatory AU-rich elements (AREs) in their 3′-untranslated regions (3′-UTR) can be relieved of miRNA repression under cellular stress in a process involving the embryonic lethal and altered vision family ARE-binding protein HuR. The HuR-mediated derepression occurred even when AREs were positioned at a considerable distance from the miRNA sites raising questions about the mechanism of HuR action. Here, we show that the relief of miRNA-mediated repression involving HuR can be recapitulated in different in vitro systems in the absence of stress, indicating that HuR alone is sufficient to relieve the miRNA repression upon binding to RNA ARE. Using in vitro assays with purified miRISC and recombinant HuR and its mutants, we show that HuR, likely by its property to oligomerize along RNA, leads to the dissociation of miRISC from target RNA even when miRISC and HuR binding sites are positioned at a distance. Further, we demonstrate that HuR association with AREs can also inhibit miRNA-mediated deadenylation of mRNA in the Krebs-2 ascites extract, in a manner likewise depending on the potential of HuR to oligomerize

SEGMENTATION OF BRAIN MR IMAGES USING FUZZY SETS AND MODIFIED CO-OCCURRENCE MATRIX

matrix, fuzzy correlation. Image segmentation is an indispensable process in the visualization of human tissues, particularly during clinical analysis of magnetic resonance (MR) images. A robust segmentation technique based on fuzzy set theory for brain MR images is proposed in this paper. The histogram of the given image is thresholded according to the similarity between gray levels. The similarity is assessed through second order fuzzy correlation. To calculate the second order fuzzy correlation, a modified co-occurrence matrix is used to extract the local information more accurately. Two parameters- ambiguity and the strength of ambiguity, are introduced to determine the thresholds of the given histogram. The effectiveness of the proposed algorithm, along with a comparison with other methods, has been demonstrated on a set of brain MR images.

Effect of cyclodextrin encapsulation on the photocyclization of diphenylamine: Cavity imposed restriction on the reaction rate

The kinetics of the photocyclization of diphenylamine (DPA) to carbazole (CAZL) has been studied fluorometrically in air-equilibrated aqueous solution as well as in constrained microheterogeneous media provided by [alpha]-, [beta]-, and [gamma]- cyclodextrins (CDs). It is observed that the fluorophore is embedded within the CD cavities without any alteration of the overall reaction quantum yield in the different environments. However, the rate of the photoreaction is modified remarkably within the CD environments. A restriction on the intramolecular rotation of the phenyl planes of DPA, imposed by the steric rigidity within the CD cavities, has been ascribed to be responsible for the suppression of the reaction rates within the CD environments. A semi-empirical (AM1) calculation gives the molecular dimension of the substrate and corroborates the proposition from a consideration of the cavity size of the different cyclodextrins.http://www.sciencedirect.com/science/article/B6TGR-44WJT2F-D/1/fbeee114a055a066bec9406d2538f43

Perspectives About Modulating Host Immune System in Targeting SARS-CoV-2 in India

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of coronavirus induced disease-2019 (COVID-19), is a type of common cold virus responsible for a global pandemic which requires immediate measures for its containment. India has the world’s largest population aged between 10 and 40 years. At the same time, India has a large number of individuals with diabetes, hypertension and kidney diseases, who are at a high risk of developing COVID-19. A vaccine against the SARS-CoV-2, may offer immediate protection from the causative agent of COVID-19, however, the protective memory may be short-lived. Even if vaccination is broadly successful in the world, India has a large and diverse population with over one-third being below the poverty line. Therefore, the success of a vaccine, even when one becomes available, is uncertain, making it necessary to focus on alternate approaches of tackling the disease. In this review, we discuss the differences in COVID-19 death/infection ratio between urban and rural India; and the probable role of the immune system, co-morbidities and associated nutritional status in dictating the death rate of COVID-19 patients in rural and urban India. Also, we focus on strategies for developing masks, vaccines, diagnostics and the role of drugs targeting host-virus protein-protein interactions in enhancing host immunity. We also discuss India’s strengths including the resources of medicinal plants, good food habits and the role of information technology in combating COVID-19. We focus on the Government of India’s measures and strategies for creating awareness in the containment of COVID-19 infection across the country

Copper(II)/tin(II) reagent for allylation, propargylation, alkylation, and benzylation of disulfides and elemental sulfur: new insight into the "Copper Effect"

Organic bromides and iodides react with diorganodisulfides in the presence of stannous chloride and catalytic cupric halide, giving rise to corresponding unsymmetrical sulfides. Similar reactions but with elemental sulfur provide trisulfides and tetrasulfides. The reactions proceed by copper thiolate as principal reactive intermediate