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81.
Priyanka Das Abhijit Basu Aditi Biswas Darshana Poddar Joel Andrews Sailen Barik Anton A. Komar Barsanjit Mazumder 《Molecular and cellular biology》2013,33(15):2829-2842
In contrast to prokaryotes, the precise mechanism of incorporation of ribosomal proteins into ribosomes in eukaryotes is not well understood. For the majority of eukaryotic ribosomal proteins, residues critical for rRNA binding, a key step in the hierarchical assembly of ribosomes, have not been well defined. In this study, we used the mammalian ribosomal protein L13a as a model to investigate the mechanism(s) underlying eukaryotic ribosomal protein incorporation into ribosomes. This work identified the arginine residue at position 68 of L13a as being essential for L13a binding to rRNA and incorporation into ribosomes. We also demonstrated that incorporation of L13a takes place during maturation of the 90S preribosome in the nucleolus, but that translocation of L13a into the nucleolus is not sufficient for its incorporation into ribosomes. Incorporation of L13a into the 90S preribosome was required for rRNA methylation within the 90S complex. However, mutations abolishing ribosomal incorporation of L13a did not affect its ability to be phosphorylated or its extraribosomal function in GAIT element-mediated translational silencing. These results provide new insights into the mechanism of ribosomal incorporation of L13a and will be useful in guiding future studies aimed at fully deciphering mammalian ribosome biogenesis. 相似文献
82.
Pritha Basu 《Journal of biomolecular structure & dynamics》2013,31(12):2594-2605
A detailed investigation on the interaction of two benzophenanthridine alkaloids, sanguinarine (SGR) and chelerythrine (CHL), with the double-stranded (ds), heat-denatured (hd), and single-stranded (ss) DNA was performed by spectroscopy and calorimetry techniques. Binding to the three DNA conformations leads to quenching of fluorescence of SGR and enhancement in the fluorescence of CHL. The binding was cooperative for both of the alkaloids with all the three DNA conformations. The binding constant values of both alkaloids with the ds DNA were in the order of 106 M?1; binding was weak with hd and much weaker to the ss DNA. The fluorescence emission of the alkaloid molecules bound to the ds and hd DNAs was quenched much less compared to those bound to the ss DNA based on competition with the anionic quencher KI. For both double stranded and heat denatured structures the emission of the bound alkaloid molecules was polarized significantly and strong energy transfer from the DNA bases to the alkaloid molecules occurred. Intercalation of SGR and CHL to ds, hd, and ss DNA was proved from these fluorescence results. Calorimetric studies suggested that the binding to all DNA conformations was both enthalpy and entropy favored. Both the alkaloids preferred double-helical regions for binding, but SGR was a stronger binder than CHL to all the three DNA structures. 相似文献
83.
84.
Chandipura virus (CHPV; genus Vesiculovirus, family Rhabdoviridae) is an emerging tropical pathogen with a case fatality rate of 55 to 75% that predominantly affects children in the age group of 2 to 16 years. Although it has been established as a neurotropic virus causing encephalitis, the molecular pathology leading to neuronal death is unknown. The present study elucidates for the first time the mechanism of cell death in neurons after CHPV infection that answers the basic cause of CHPV-mediated neurodegeneration. Through various cell death assays in vitro and in vivo, a relationship between viral replication within neuron and neuronal apoptosis has been established. We report that expression of CHPV phosphoprotein increases up to 6 h postinfection and diminishes thereafter in neuronal cell lines, signifying the replicative phase of CHPV. Various analyses conducted during the investigation established that CHPV-infected neurons are undergoing apoptosis through an extrinsic pathway mediated through the Fas-associated death domain (FADD) following activation of caspase-8 and -3 and prominent cleavage of poly(ADP-ribose) polymerase (PARP). Knocking down the expression of caspase-3, the final executioner of apoptosis, in a neuronal cell line by endoribonuclease-prepared small interfering RNA (siRNA) validated its pivotal role in CHPV-mediated neurodegeneration by showing reduction in apoptosis after CHPV infection. 相似文献
85.
Sini Thomas Anjali Anand Viswanthan Chinnusamy Anil Dahuja Sudipta Basu 《Acta Physiologiae Plantarum》2013,35(12):3401-3411
Chickpea seeds of Pusa 1053 (Mediterranean) and Pusa 256 (native) were magnetoprimed with 100 mT static magnetic field for 1 h to evaluate the effect of magnetopriming on germination of seeds under saline conditions. Enhanced rate of germination and seedling growth parameters (root and shoot length, and vigour indices) under different salinity levels indicated that magnetopriming was more effective in alleviating salinity stress at early seedling stage in Pusa 1053 as compared to Pusa 256. Dynamics of seed water absorption in magnetoprimed seeds showed increased water uptake in Pusa 1053 under non-saline as compared to saline conditions. This could have resulted in faster hydration of enzymes in primed seeds leading to higher rate of germination. Total amylase, protease and dehydrogenase activities were higher in primed seeds as compared to unprimed seeds under both non-saline and saline conditions. Production of superoxide radicals was enhanced in germinating seeds of both the genotypes under salinity irrespective of priming. Increased levels of hydrogen peroxide in germinating magnetoprimed seeds, under both the growing conditions, suggested its role in promotion of germination. Our results showed that magnetopriming of dry seeds of chickpea can be effectively used as a pre-sowing treatment for mitigating adverse effects of salinity at seed germination and early seedling growth. 相似文献
86.
Subhabrata Kar Priyanka Bajaj Rajan K. Tripathy Abhay H. Pande 《The Journal of membrane biology》2013,246(6):443-452
Oxidative modification of phospholipids generates a variety of oxidized phospholipid (Ox-PL) species which differ considerably in their chemical compositions and molecular structures. Recent results suggest that even closely related Ox-PL species can have considerably different biological effects. However, the molecular mechanism for this is not yet clear. In truncated Ox-PLs (tOx-PLs) the fatty acyl chain is shorter in length than the parent nonoxidized phospholipid molecules and contains a polar functional group(s). In a previous study we showed that two closely related tOx-PL species having a similar polar functional group and differing only in the length of the oxidized fatty acyl chain exerts significantly different effects on the physicochemical properties of the nonoxidized phospholipid particles containing these lipids (Kar et al., Chem Phys Lipids 164:54–61, 2011). In this study we have characterized the effect of polar functional groups of oxidized fatty acyl chain on the physicochemical properties of the nonoxidized phospholipid particles containing these lipids. Our results show that Ox-PL species differing only in the chemical nature of polar functional groups in their oxidized fatty acyl chain modify the properties of nonoxidized phospholipid particles containing them in a distinctive way. These results indicate that different species of Ox-PLs induce unique changes in the physicochemical properties of lipid particles/membranes containing them and that this may lead to their different biological effects. 相似文献
87.
Polycyclic aromatic hydrocarbons and their nitro derivatives are culprits of the detrimental health effects of environmental pollution. These hydrophobic compounds metabolize to reactive species and attach to DNA producing bulky lesions, such as N-[deoxyguanosine-8-yl]-1-aminopyrene (APG), in genomic DNA. The bulky adducts block DNA replication by high-fidelity polymerases and compromise replication fidelities and efficiencies by specialized lesion bypass polymerases. Here we present three crystal structures of the DNA polymerase Dpo4, a model translesion DNA polymerase of the Y family, in complex with APG-lesion-containing DNA in pre-insertion and extension stages. APG is captured in two conformations in the pre-insertion complex; one is highly exposed to the solvent, whereas the other is harbored in a shallow cleft between the finger and unique Y family little finger domain. In contrast, APG is in a single conformation at the extension stage, in which the pyrene ring is sandwiched between the little finger domain and a base from the turning back single-stranded template strand. Strikingly, a nucleotide intercalates the DNA helix to form a quaternary complex with Dpo4, DNA, and an incoming nucleotide, which stabilizes the distorted DNA structure at the extension stage. The unique APG DNA conformations in Dpo4 inhibit DNA translocation through the polymerase active site for APG bypass. We also modeled an insertion complex that illustrates a solvent-exposed pyrene ring contributing to an unstable insertion state. The structural work combined with our lesion replication assays provides a novel structural mechanism on bypass of DNA adducts containing polycyclic aromatic hydrocarbon moieties. 相似文献
88.
Debarati Basu Yan Liang Xiao Liu Klaus Himmeldirk Ahmed Faik Marcia Kieliszewski Michael Held Allan M. Showalter 《The Journal of biological chemistry》2013,288(14):10132-10143
Although plants contain substantial amounts of arabinogalactan proteins (AGPs), the enzymes responsible for AGP glycosylation are largely unknown. Bioinformatics indicated that AGP galactosyltransferases (GALTs) are members of the carbohydrate-active enzyme glycosyltransferase (GT) 31 family (CAZy GT31) involved in N- and O-glycosylation. Six Arabidopsis GT31 members were expressed in Pichia pastoris and tested for enzyme activity. The At4g21060 gene (named AtGALT2) was found to encode activity for adding galactose (Gal) to hydroxyproline (Hyp) in AGP protein backbones. AtGALT2 specifically catalyzed incorporation of [14C]Gal from UDP-[14C]Gal to Hyp of model substrate acceptors having AGP peptide sequences, consisting of non-contiguous Hyp residues, such as (Ala-Hyp) repetitive units exemplified by chemically synthesized (AO)7 and anhydrous hydrogen fluoride-deglycosylated d(AO)51. Microsomal preparations from Pichia cells expressing AtGALT2 incorporated [14C]Gal to (AO)7, and the resulting product co-eluted with (AO)7 by reverse-phase HPLC. Acid hydrolysis of the [14C]Gal-(AO)7 product released 14C-radiolabel as Gal only. Base hydrolysis of the [14C]Gal-(AO)7 product released a 14C-radiolabeled fragment that co-eluted with a Hyp-Gal standard after high performance anion-exchange chromatography fractionation. AtGALT2 is specific for AGPs because substrates lacking AGP peptide sequences did not act as acceptors. Moreover, AtGALT2 uses only UDP-Gal as the substrate donor and requires Mg2+ or Mn2+ for high activity. Additional support that AtGALT2 encodes an AGP GALT was provided by two allelic AtGALT2 knock-out mutants, which demonstrated lower GALT activities and reductions in β-Yariv-precipitated AGPs compared with wild type plants. Confocal microscopic analysis of fluorescently tagged AtGALT2 in tobacco epidermal cells indicated that AtGALT2 is probably localized in the endomembrane system consistent with its function. 相似文献
89.
90.
Pollen grains of M, and C, generation plants of Trichosanthes anguina L. were studied after treatment of seeds with X-rays and colchicine respectively. Pollen sterility increased with increase in X-ray dose and colchicine concentration. The polar axis of X-irradiated populations was shorter than that of controls. But colchicine treatment resulted in larger pollen grains than the controls, although the exine did not increase as much. Ex-perimentally-produced tetraploids had larger pollen grains than diploids and triploids. The triploids were characterised by changes in pore morphology. Of 293 treated plants examined, 11 aberrant plants were isolated in the M, and C, generations. These plants had large and small fertile pollen grains, and also showed treatment effects in external morphology and chromosomal aberration during meiosis. The changes in polar diameter were not associated with variation in chromosomal material. 相似文献