Publications by authors named "Saheli Chowdhury"

11 Publications

  • Page 1 of 1

Neutrophilic inflammation in asthma and defective epithelial translational control.

Eur Respir J 2019 08 15;54(2). Epub 2019 Aug 15.

Amsterdam UMC, University of Amsterdam, Dept of Respiratory Medicine, Amsterdam, The Netherlands

Neutrophilic inflammation in asthma is associated with interleukin (IL)-17A, corticosteroid-insensitivity and bronchodilator-induced forced expiratory volume in 1 s (FEV) reversibility. IL-17A synergises with tumour necrosis factor (TNF)-α in the production of the neutrophil chemokine CXCL-8 by primary bronchial epithelial cells (PBECs).We hypothesised that local neutrophilic inflammation in asthma correlates with IL-17A and TNF-α-induced CXCL-8 production by PBECs from asthma patients.PBECs from most asthma patients displayed an exaggerated CXCL-8 production in response to TNF-α and IL-17A, but not to TNF-α alone, and which was also insensitive to corticosteroids. This hyperresponsiveness of PBECs strongly correlated with CXCL-8 levels and neutrophil numbers in bronchoalveolar lavage from the corresponding patients, but not with that of eosinophils. In addition, this hyperresponsiveness also correlated with bronchodilator-induced FEV % reversibility. At the molecular level, epithelial hyperresponsiveness was associated with failure of the translational repressor T-cell internal antigen-1 related protein (TiAR) to translocate to the cytoplasm to halt CXCL-8 production, as confirmed by TiAR knockdown. This is in line with the finding that hyperresponsive PBECs also produced enhanced levels of other inflammatory mediators.Hyperresponsive PBECs in asthma patients may underlie neutrophilic and corticosteroid-insensitive inflammation and a reduced FEV, irrespective of eosinophilic inflammation. Normalising cytoplasmic translocation of TiAR is a potential therapeutic target in neutrophilic, corticosteroid-insensitive asthma.
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http://dx.doi.org/10.1183/13993003.00547-2019DOI Listing
August 2019

Monitoring of soil radon by SSNTD in Eastern India in search of possible earthquake precursor.

J Environ Radioact 2018 Apr 30;184-185:63-70. Epub 2018 Jan 30.

Centre for Astroparticle Physics and Space Science, Bose Institute, Block-EN, Sector-V, Bidhannagar, Kolkata 700091, India. Electronic address:

The present paper deals with monitoring soil radon-222 concentration at two different locations, designated Site A and Site B, 200 m apart at Jadavpur University campus, Kolkata, India, with a view to find possible precursors for the earthquakes that occurred within a few hundred kilometers from the monitoring site. The solid state nuclear track detector CR-39 has been used for detection of radon gas coming out from soil. Radon-222 time series at both locations during the period August 2012-December 2013 have been analysed. Distinct anomalies in the soil radon time series have been observed for seven earthquakes of magnitude greater than 4.0 M that occurred during this time. Of these, radon anomalies for two earthquakes have been observed at both locations A and B. Absence of anomalies for some other earthquakes has been discussed, and the observations have been compared with some earthquake precursor models.
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http://dx.doi.org/10.1016/j.jenvrad.2018.01.009DOI Listing
April 2018

RADIOLOGICAL IMPACT OF SOME COMMON FOODS OF SOUTHERN PART OF WEST BENGAL, INDIA.

Radiat Prot Dosimetry 2018 Apr;179(2):169-178

School of Studies in Environmental Radiation and Archaeological Sciences, Jadavpur University, Kolkata 700032, India.

An appreciable portion of human exposure to natural radioactivity comes from food and drinking water. Gross alpha radioactivity has been measured in thirty one food items consumed almost every day by the people of southern part of West Bengal, India, by using the solid state nuclear track detector LR-115. The annual effective doses due to intake of alpha-emitting radionuclides through these food items have also been estimated, and the total average annual dose received by an adultthrough ingestion of these foodstuffs calculated, considering the food habit of the people of the region. The total average annual dose is below the 1 mSv y-1 limit proposed by WHO, and over half of this annual dose comes from consumption of cereals.
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http://dx.doi.org/10.1093/rpd/ncx246DOI Listing
April 2018

IL-17 attenuates degradation of ARE-mRNAs by changing the cooperation between AU-binding proteins and microRNA16.

PLoS Genet 2013 26;9(9):e1003747. Epub 2013 Sep 26.

Department of Respiratory Medicine, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands ; Department of Experimental Immunology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.

Interleukin 17A (IL-17), a mediator implicated in chronic and severe inflammatory diseases, enhances the production of pro-inflammatory mediators by attenuating decay of the encoding mRNAs. The decay of many of these mRNAs depends on proteins (AUBps) that target AU-rich elements in the 3'-untranslated region of mRNAs and facilitate either mRNA decay or stabilization. Here we show that AUBps and the target mRNA assemble in a novel ribonucleoprotein complex in the presence of microRNA16 (miR16), which leads to the degradation of the target mRNA. Notably, IL-17 attenuates miR16 expression and promotes the binding of stabilizing AUBps over that of destabilizing AUBps, reducing mRNA decay. These findings indicate that miR16 independently of a seed sequence, directs the competition between degrading and stabilizing AUBps for target mRNAs. Since AUBps affect expression of about 8% of the human transcriptome and miR16 is ubiquitously expressed, IL-17 may in addition to inflammation affect many other cellular processes.
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http://dx.doi.org/10.1371/journal.pgen.1003747DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3784493PMC
March 2014

Protein folding by domain V of Escherichia coli 23S rRNA: specificity of RNA-protein interactions.

J Bacteriol 2008 May 29;190(9):3344-52. Epub 2008 Feb 29.

University College of Science, Department of Biophysics, Molecular Biology and Genetics, 92 A.P.C. Road, Kolkata-700009, India.

The peptidyl transferase center, present in domain V of 23S rRNA of eubacteria and large rRNA of plants and animals, can act as a general protein folding modulator. Here we show that a few specific nucleotides in Escherichia coli domain V RNA bind to unfolded proteins and, as shown previously, bring the trapped proteins to a folding-competent state before releasing them. These nucleotides are the same for the proteins studied so far: bovine carbonic anhydrase, lactate dehydrogenase, malate dehydrogenase, and chicken egg white lysozyme. The amino acids that interact with these nucleotides are also found to be specific in the two cases tested: bovine carbonic anhydrase and lysozyme. They are either neutral or positively charged and are present in random coils on the surface of the crystal structure of both the proteins. In fact, two of these amino acid-nucleotide pairs are identical in the two cases. How these features might help the process of protein folding is discussed.
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http://dx.doi.org/10.1128/JB.01800-07DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2347393PMC
May 2008

In vitro protein folding by E. coli ribosome: unfolded protein splitting 70S to interact with 50S subunit.

Biochem Biophys Res Commun 2008 Feb 7;366(2):598-603. Epub 2007 Dec 7.

Department of Biophysics, Molecular Biology and Genetics, University College of Science, 92 A.P.C. Road, Kolkata 700009, India.

Folding of unfolded protein on Escherichia coli 70S ribosome is accompanied by rapid dissociation of the ribosome into 50S and 30S subunits. The dissociation rate of 70S ribosome with unfolded protein is much faster than that caused by combined effect of translation and polypeptide release factors known to be involved in the dissociation of ribosome into subunits. The protein then reaches a "folding competent" state on 50S and is released to take up native conformation by itself. Release before attaining the folding competent state or prevention of release by cross-linking it with ribosome, would not allow the protein to get back to its native conformation.
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http://dx.doi.org/10.1016/j.bbrc.2007.11.143DOI Listing
February 2008

Molecular basis for temperature sensing by an RNA thermometer.

EMBO J 2006 Jun 18;25(11):2487-97. Epub 2006 May 18.

Institute of Molecular Biology and Biophysics, ETH Zurich, Zürich, Switzerland.

Regulatory RNA elements, like riboswitches, respond to intracellular signals by three-dimensional (3D) conformational changes. RNA thermometers employ a similar strategy to sense temperature changes in the cell and regulate the translational machinery. We present here the first 3D NMR structure of the functional domain of a highly conserved bacterial RNA thermometer containing the ribosome binding site that remains occluded at normal temperatures (30 degrees C). We identified a region adjacent to the Shine-Dalgarno sequence that has a network of weak hydrogen bonds within the RNA helix. With the onset of heat shock at 42 degrees C, destabilisation of the RNA structure initiates at this region and favours the release of the ribosome binding site and of the start codon. Deletion of a highly conserved G residue leads to the formation of a stable regular RNA helix that loses thermosensing ability. Our results indicate that RNA thermometers are able to sense temperature changes without the aid of accessory factors.
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http://dx.doi.org/10.1038/sj.emboj.7601128DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1478195PMC
June 2006

RNA thermometers.

FEMS Microbiol Rev 2006 Jan;30(1):3-16

Lehrstuhl für Biologie der Mikroorganismen, Ruhr-Universität Bochum, Bochum, Germany.

Temperature is an important parameter that free-living cells monitor constantly. The expression of heat-shock, cold-shock and some virulence genes is coordinated in response to temperature changes. Apart from protein-mediated transcriptional control mechanisms, translational control by RNA thermometers is a widely used regulatory strategy. RNA thermometers are complex RNA structures that change their conformation in response to temperature. Most, but not all, RNA thermometers are located in the 5'-untranslated region and mask ribosome-binding sites by base pairing at low temperatures. Melting of the structure at increasing temperature permits ribosome access and translation initiation. Different cis-acting RNA thermometers and a trans-acting thermometer will be presented.
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http://dx.doi.org/10.1111/j.1574-6976.2005.004.xDOI Listing
January 2006

Temperature-controlled structural alterations of an RNA thermometer.

J Biol Chem 2003 Nov 8;278(48):47915-21. Epub 2003 Sep 8.

Institut of Microbiology, Eidgenössische Technische Hochschule, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland.

Thermoresponsive structures in the 5'-untranslated region of mRNA are known to control translation of heat shock and virulence genes. Expression of many rhizobial heat shock genes is regulated by a conserved sequence element called ROSE for repression of heat shock gene expression. This cis-acting, untranslated mRNA is thought to prevent ribosome access at low temperature through an extended secondary structure, which partially melts when the temperature rises. We show here by a series of in vivo and in vitro approaches that ROSE is a sensitive thermometer responding in the physiologically relevant temperature range between 30 and 40 degrees C. Point mutations predicted to disrupt base pairing enhanced expression at 30 degrees C. Compensatory mutations restored repression, emphasizing the importance of secondary structures in the sensory RNA. Only moderate inducibility of a 5'-truncated ROSE variant suggests that interactions between individual stem loops coordinate temperature sensing. In the presence of a complementary oligonucleotide, the functionally important stem loop of ROSE was rendered susceptible to RNase H treatment at heat shock temperatures. Since major structural rearrangements were not observed during UV and CD spectroscopy, subtle structural changes involving the Shine-Dalgarno sequence are proposed to mediate translational control. Temperature perception by the sensory RNA is an ordered process that most likely occurs without the aid of accessory factors.
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http://dx.doi.org/10.1074/jbc.M306874200DOI Listing
November 2003

23S rRNA assisted folding of cytoplasmic malate dehydrogenase is distinctly different from its self-folding.

Nucleic Acids Res 2002 Jun;30(11):2390-7

Department of Biophysics, Molecular Biology and Genetics, University College of Science, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India.

The role of the 50S particle of Escherichia coli ribosome and its 23S rRNA in the refolding and subunit association of dimeric porcine heart cytoplasmic malate dehydrogenase (s-MDH) has been investigated. The self-reconstitution of s-MDH is governed by two parallel pathways representing the folding of the inactive monomeric and the dimeric intermediates. However, in the presence of these folding modulators, only one first order kinetics was observed. To understand whether this involved the folding of the monomers or the dimers, subunit association of s-MDH was studied using fluorescein-5-isothiocyanate-rhodamine-isothiocyanate (FITC-RITC) fluorescence energy transfer and chemical cross-linking with gluteraldehyde. The observation suggests that during refolding the interaction of the unstructured monomers of s-MDH with these ribosomal folding modulators leads to very fast formation of structured monomers that immediately dimerise. These inactive dimers then fold to the native ones, which is the rate limiting step in 23S or 50S assisted refolding of s-MDH. Furthermore, the sequential action of the two fragments of domain V of 23S rRNA has been investigated in order to elucidate the mechanism. The central loop of domain V of 23S rRNA (RNA1) traps the monomeric intermediates, and when they are released by the upper stem-loop region of the domain V of 23S rRNA (RNA2) they are already structured enough to form dimeric intermediates which are directed towards the proper folding pathway.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC117201PMC
http://dx.doi.org/10.1093/nar/30.11.2390DOI Listing
June 2002

Mutations in domain V of the 23S ribosomal RNA of Bacillus subtilis that inactivate its protein folding property in vitro.

Nucleic Acids Res 2002 Mar;30(5):1278-85

Department of Biophysics, Molecular Biology and Genetics, University of Calcutta, 92 A.P.C. Road, Calcutta 700 009, India.

The active site of a protein folding reaction is in domain V of the 23S rRNA in the bacterial ribosome and its homologs in other organisms. This domain has long been known as the peptidyl transferase center. Domain V of Bacillus subtilis is split into two segments, the more conserved large peptidyl transferase loop (RNA1) and the rest (RNA2). These two segments together act as a protein folding modulator as well as the complete domain V RNA. A number of site-directed mutations were introduced in RNA1 and RNA2 of B.subtilis, taking clues from reports of these sites being involved in various steps of protein synthesis. For example, sites like G2505, U2506, U2584 and U2585 in Escherichia coli RNA1 region are protected by deacylated tRNA at high Mg2+ concentration and A2602 is protected by amino acyl tRNA when the P site remains occupied already. Mutations A2058G and A2059G in the RNA1 region render the ribosome Ery(r )in E.coli and Lnc(r )in tobacco chloroplast. Sites in P loop G2252 and G2253 in E.coli are protected against modification by the CCA end of the P site bound tRNA. Mutations were introduced in corresponding nucleotides in B.subtilis RNA1 and RNA2 of domain V. The mutants were tested for refolding using unfolded protein binding assays with unfolded carbonic anhydrase. In the protein folding assay, the mutants showed partial to complete loss of this activity. In the filter binding assay for the RNA-refolding protein complex, the mutants showed an extent of protein binding that agreed well with their protein folding activity.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC101228PMC
http://dx.doi.org/10.1093/nar/30.5.1278DOI Listing
March 2002