Subcellular dynamics of variants of SG2NA in NIH3T3 fibroblasts

SG2NA, a WD40 repeat protein of the Striatin subfamily, has four splicing and one messenger RNA edit variants. It is fast emerging as a scaffold for multimeric signaling complexes with roles in tissue development and disease. The green fluorescent protein (GFP)‐tagged variants of SG2NA were ectopically expressed in NIH3T3 cells and their modulation by serum and GSK3β‐ERK signaling were monitored. The 87, 78, and 35 kDa variants showed a biphasic modulation by serum till 24 h but the 52 kDa variant remained largely unresponsive. Inhibition of phosphatases by okadaic acid increased the levels of the endogenous 78 kDa and the ectopically expressed GFP‐tagged 87 and 78 kDa SG2NAs. Contrastingly, okadaic acid treatment reduced the level of GFP‐tagged 35 kDa SG2NA, suggesting differential modes of their stability through phosphorylation‐dephosphorylation. The inhibition of GSK3β by LiCl showed a gradual decrease in the levels of 78 kDa. In the case of the other variants viz, GFP‐tagged 35, 52, and 87 kDa, inhibition of GSK3β caused an initial increase followed by a decrease with a subtle difference in kinetics and intensities. Similar results were also seen upon inhibition of GSK3β by small interfering RNA. All the variants showed an increase followed by a decrease upon inhibition of extracellular‐signal‐regulated‐kinase (ERK). These variants are localized in the plasma membrane, endoplasmic reticulum, mitochondria, and the nucleus with different propensities and no discernable subcellular distribution was seen upon stimulation by serum and the inhibition of phosphatases, GSK3β, and ERK. Taken together, the variants of SG2NA are modulated by the kinase‐phosphatase network in a similar but characteristic manner.     

A Study on Cadmium Phytoremediation Potential of Indian Mustard,Brassica juncea

The objective of this study was to investigate Cd phytoremediation ability of Indian mustard, Brassica juncea. The study was conducted with 25, 50, 100, 200 and 400 mg Kg^?1 CdCl₂ in laboratory for 21 days and Cd concentrations in the root, shoot and leaf tissues were estimated by atomic absorption spectroscopy. The plant showed high Cd tolerance of up to 400 mg Kg^?1 but there was a general trend of decline in the root and shoot length, tissue biomass, leaf chlorophyll and carotenoid contents. The tolerance index (TI) of plants were calculated taking both root and shoot lengths as variables. The maximum tolerance (TI _shoot = 87.4 % and TI _root = 89.6 %) to Cd toxicity was observed at 25 mg Kg^?1, which progressively decreased with increase in dose. The highest shoot (10791 μg g^?1 dry wt) and root (9602 μg g^?1 dry wt) Cd accumulation was achieved at 200 mg kg^?1 Cd treatment and the maximum leaf Cd accumulation was 10071.6 μg g^?1 dry wt achieved at 100 mg Kg^?1 Cd, after 21 days of treatment. The enrichment coefficient and root to shoot translocation factor were calculated, which, pointed towards the suitability of Indian mustard for removing Cd from soil.     

Host modification of the adherence properties of Chlamydia trachomatis

The adherence of Chlamydia trachomatis LGV440(L1) to human HeLa 229 and mouse McCoy cells was stimulated by the lectin wheat germ agglutinin (WGA) and inhibited by the sugars N-acetyl-D-glucosamine, N-acetyl-D-galactosamine and chitobiose, but only when the chlamydiae had been passaged several times in HeLa cells. After passage in McCoy cells, the lectin and the sugars elicited little response. The non-LGV serovar UW-31(K), however, differed from LGV440(L1) in that, regardless of passage, the lectin and sugar effects were observed only in HeLa cells. Affinity chromatography on WGA-agarose confirmed that HeLa-grown LGV440(L1) bound to a significantly greater extent relative to McCoy-grown chlamydiae. In addition, participation of heterogeneous chlamydial ligands was suggested by the observation that the adherence of heated (60 degrees C, 5 min) UW-31(K) to HeLa cells at 37 degrees C was not inhibited at all, but at 5 degrees C, the adherence rate was greatly reduced, indicating the participation of heat-stable as well as heat-labile ligands. These data are interpreted to indicate that the passage history of C. trachomatis results in the acquisition of altered surface components that participate in the initial interaction of the bacterium with the host.     

Manipulation of inositol metabolism for improved plant survival under stress: a “network engineering approach”

Emergence of high-throughput sequencing tools and omics technologies paved the way for systems biology in last decade. While we have started to look at the biology of the plant in a more unified manner, the integration of such knowledge in agricultural biotechnology has become an arena of potential interest. The network of several central molecules operating in various life and developmental processes are now more adequately known, and fine tuning of such molecule pools, if connected to stress response, can result in enhanced stress tolerance of plants.This review interprets the potential of manipulation of myo-inositol and its derivatives in generation of transgenic crop plants. Being a molecule of central importance in plant life, inositol is connected to numerous life processes. The exploration of such pathways indicates that inositol itself and many of its derivatives can impart abiotic stress tolerance (against salinity, dehydration, chilling or oxidative stress) to plants when overexpressed. We propose that engineering inositol metabolic network is a potential approach towards stress-tolerant transgenic crop plant generation and thus its exploitation in agricultural biotechnology is the call of time.     

Reactive oxygen species mediate microRNA-302 regulation of AT-rich interacting domain 4a and C-C motif ligand 5 expression during transitions between quiescence and proliferation

Normal cell growth consists of two distinct phases, quiescence and proliferation. Quiescence, or G(0), is a reversible growth arrest in which cells retain the ability to reenter the proliferative cycle (G(1), S, G(2), and M). Although not actively dividing, quiescent cells are metabolically active and quiescence is actively maintained. Our results from microRNA PCR arrays and Taqman PCR assays showed a significant decrease (4-fold) in miR-302 levels during quiescence compared to proliferating normal human fibroblasts, suggesting that miR-302 could regulate cellular proliferation. Results from a Q-RT-PCR and dual-luciferase-3'-UTR reporter assays identified ARID4a (AT-rich interacting domain 4a, also known as RBP1) and CCL5 (C-C motif ligand 5) as targets for miR-302. Ionizing radiation decreased miR-302 levels, which was associated with an increase in its target mRNA levels, ARID4a and CCL5. Such an inverse correlation was also observed in cells treated with hydrogen peroxide as well as SOD2-overexpressing cells. Overexpression of miR-302 suppresses ARID4a and CCL5 mRNA levels, and increased the percentage of S-phase cells. These results identified miR-302 as an ROS-sensitive regulator of ARID4a and CCL5 mRNAs as well as demonstrate a regulatory role of miR-302 during quiescence and proliferation.     

Hereditary hemochromatosis protein, HFE, interaction with transferrin receptor 2 suggests a molecular mechanism for mammalian iron sensing

HFE and transferrin receptor 2 (TFR2) are membrane proteins integral to mammalian iron homeostasis and associated with human hereditary hemochromatosis. Here we demonstrate that HFE and TFR2 interact in cells, that this interaction is not abrogated by disease-associated mutations of HFE and TFR2, and that TFR2 competes with TFR1 for binding to HFE. We propose a new model for the mechanism of iron status sensing that results in the regulation of iron homeostasis.     

Molecular and functional interactions between Escherichia coli nucleoside-diphosphate kinase and the uracil-DNA glycosylase Ung

Escherichia coli nucleoside-diphosphate kinase (Ndk) catalyzes nucleoside triphosphate synthesis and maintains intracellular triphosphate pools. Mutants of E. coli lacking Ndk exhibit normal growth rates but show a mutator phenotype that cannot be entirely attributed to the absence of Ndk catalytic activity or to an imbalance in cellular triphosphates. It has been suggested previously that Ndk, similar to its human counterparts, possesses nuclease and DNA repair activities, including the excision of uracil from DNA, an activity normally associated with the Ung and Mug uracil-DNA glycosylases (UDGs) in E. coli. Here we have demonstrated that recombinant Ndk purified from wild-type E. coli contains significant UDG activity that is not intrinsic, but rather, is a consequence of a direct physical and functional interaction between Ung and Ndk, although a residual amount of intrinsic UDG activity exists as well. Co-purification of Ung and Ndk through multicolumn low pressure and nickel-nitrilotriacetic acid affinity chromatography suggests that the interaction occurs in a cellular context, as was also suggested by co-immunoprecipitation of endogenous Ung and Ndk from cellular extracts. Glutathione S-transferase pulldown and far Western analyses demonstrate that the interaction also occurs at the level of purified protein, suggesting that it is specific and direct. Moreover, significant augmentation of Ung catalytic activity by Ndk was observed, suggesting that the interaction between the two enzymes is functionally relevant. These findings represent the first example of Ung interacting with another E. coli protein and also lend support to the recently discovered role of nucleoside-diphosphate kinases as regulatory components of multiprotein complexes.