Motifs Q and I are required for ATP hydrolysis but not for ATP binding in SWI2/SNF2 proteins

Active DNA-dependent ATPase A Domain (ADAAD) is a SWI2/SNF2 protein that hydrolyzes ATP in the presence of stem-loop DNA that contains both double-stranded and single-stranded regions. ADAAD possesses the seven helicase motifs that are a characteristic feature of all the SWI2/SNF2 proteins present in yeast as well as mammalian cells. In addition, these proteins also possess the Q motif ~17 nucleotides upstream of motif I. Using site-directed mutagenesis, we have sought to define the role of motifs Q and I in ATP hydrolysis mediated by ADAAD. We show that in ADAAD both motifs Q and I are required for ATP catalysis but not for ATP binding. In addition, the conserved glutamine present in motif Q also dictates the catalytic rate. The ability of the conserved glutamine present in motif Q to dictate the catalytic rate has not been observed in helicases. Further, the SWI2/SNF2 proteins contain a conserved glutamine, one amino acid residue downstream of motif I. This conserved glutamine, Q244 in ADAAD, also directs the rate of catalysis but is not required either for hydrolysis or for ligand binding. Finally, we show that the adenine moiety of ATP is sufficient for interaction with SWI2/SNF2 proteins. The γ-phosphate of ATP is required for inducing the conformational change that leads to ATPase activity. Thus, the SWI2/SNF2 proteins despite sequence conservation with helicases appear to behave in a manner distinct from that of the helicases.     

Centrosome positioning and primary cilia assembly orchestrate neuronal development

Establishment of axon and dendrite polarity, migration to a desired location in the developing brain, and establishment of proper synaptic connections are essential processes during neuronal development. The cellular and molecular mechanisms that govern these processes are under intensive investigation. The function of the centrosome in neuronal development has been examined and discussed in few recent studies that underscore the fundamental role of the centrosome in brain development. Clusters of emerging studies have shown that centrosome positioning tightly regulates neuronal development, leading to the segregation of cell factors, directed neurite differentiation, neuronal migration, and synaptic integration. Furthermore, cilia, that arise from the axoneme, a modified centriole, are emerging as new regulatory modules in neuronal development in conjunction with the centrosome. In this review, we focus on summarizing and discussing recent studies on centrosome positioning during neuronal development and also highlight recent findings on the role of cilia in brain development. We further discuss shared molecular signaling pathways that might regulate both centrosome and cilia associated signaling in neuronal development. Furthermore, molecular determinants such as DISC1 and LKB1 have been recently demonstrated to be crucial regulators of various aspects of neuronal development. Strikingly, these determinants might exert their function, at least in part, via the regulation of centrosome and cilia associated signaling and serve as a link between these two signaling centers. We thus include an overview of these molecular determinants.     

Prediction of stenosis behaviour in artery by neural network and multiple linear regressions

Biomechanics and Modeling in Mechanobiology - Blood flow analysis in the artery is a paramount study in the field of arterial stenosis evaluation. Studies conducted so far have reported the...     

Association of age with class VI composite restoration

Dental caries is the major oral health problem in most of the countries, affecting 60-90% of school children and a vast majority of adults. Therefore, it is of interest to evaluate the association of age with Class VI defects restored with composite restorations. We used 102 cases with data regarding Class VI composite restorations in a datasheet of 86,000 records at Saveetha Dental College, India for this study. Data shows that Class VI restorations were commonly seen in upper anterior teeth in the age group of 51 and above. The cavities prepared to receive Class VI restoration followed a conservative design of caries removal and used direct restoration techniques for reconstruction of the lost tooth structure.     

Supervillin binding to myosin II and synergism with anillin are required for cytokinesis

Cytokinesis, the process by which cytoplasm is apportioned between dividing daughter cells, requires coordination of myosin II function, membrane trafficking, and central spindle organization. Most known regulators act during late cytokinesis; a few, including the myosin II–binding proteins anillin and supervillin, act earlier. Anillin''s role in scaffolding the membrane cortex with the central spindle is well established, but the mechanism of supervillin action is relatively uncharacterized. We show here that two regions within supervillin affect cell division: residues 831–1281, which bind central spindle proteins, and residues 1–170, which bind the myosin II heavy chain (MHC) and the long form of myosin light-chain kinase. MHC binding is required to rescue supervillin deficiency, and mutagenesis of this site creates a dominant-negative phenotype. Supervillin concentrates activated and total myosin II at the furrow, and simultaneous knockdown of supervillin and anillin additively increases cell division failure. Knockdown of either protein causes mislocalization of the other, and endogenous anillin increases upon supervillin knockdown. Proteomic identification of interaction partners recovered using a high-affinity green fluorescent protein nanobody suggests that supervillin and anillin regulate the myosin II and actin cortical cytoskeletons through separate pathways. We conclude that supervillin and anillin play complementary roles during vertebrate cytokinesis.     

Dietary Selenium Supplementation Does Not Attenuate Mammary Tumorigenesis-Mediated Bone Loss in Male MMTV-PyMT Mice

Biological Trace Element Research - Bone wasting occurs during the progression of breast cancer and contributes to breast cancer mortality. We evaluated the effect of methylseleninic acid (MSeA),...     

Suppression,disaggregation, and modulation of γ‐Synuclein fibrillation pathway by green tea polyphenol EGCG

Oligomerization of γ‐Synuclein is known to have implications for both neurodegeneration and cancer. Although it is known to co‐exist with the fibrillar deposits of α‐Synuclein (Lewy bodies), a hallmark in Parkinson's disease (PD), the effect of potential therapeutic modulators on the fibrillation pathway of γ‐Syn remains unexplored. By a combined use of various biophysical tools and cytotoxicity assays we demonstrate that the flavonoid epigallocatechin‐3‐gallate (EGCG) significantly suppresses γ‐Syn fibrillation by affecting its nucleation and binds with the unstructured, nucleus forming oligomers of γ‐Syn to modulate the pathway to form α‐helical containing higher‐order oligomers (~158 kDa and ~ 670 kDa) that are SDS‐resistant and conformationally restrained in nature. Seeding studies reveal that these oligomers although “on‐pathway” in nature, are kinetically retarded and rate‐limiting species that slows down fibril elongation. We observe that EGCG also disaggregates the protofibrils and mature γ‐Syn fibrils into similar SDS‐resistant oligomers. Steady‐state and time‐resolved fluorescence spectroscopy and isothermal titration calorimetry (ITC) reveal a weak non‐covalent interaction between EGCG and γ‐Syn with the dissociation constant in the mM range (K_d ~ 2–10 mM). Interestingly, while EGCG‐generated oligomers completely rescue the breast cancer (MCF‐7) cells from γ‐Syn toxicity, it reduces the viability of neuroblastoma (SH‐SY5Y) cells. However, the disaggregated oligomers of γ‐Syn are more toxic than the disaggregated fibrils for MCF‐7cells. These findings throw light on EGCG‐mediated modulation of γ‐Syn fibrillation and suggest that investigation on the effects of such modulators on γ‐Syn fibrillation is critical in identifying effective therapeutic strategies using small molecule modulators of synucleopathies.     

Identification of marker genes in Alzheimer's disease using a machine-learning model

Alzheimer''s Disease (AD) is one of the most common causes of dementia, mostly affecting the elderly population. Currently, there is no proper diagnostic tool or method available for the detection of AD. The present study used two distinct data sets of AD genes, which could be potential biomarkers in the diagnosis. The differentially expressed genes (DEGs) curated from both datasets were used for machine learning classification, tissue expression annotation and co-expression analysis. Further, CNPY3, GPR84, HIST1H2AB, HIST1H2AE, IFNAR1, LMO3, MYO18A, N4BP2L1, PML, SLC4A4, ST8SIA4, TLE1 and N4BP2L1 were identified as highly significant DEGs and exhibited co-expression with other query genes. Moreover, a tissue expression study found that these genes are also expressed in the brain tissue. In addition to the earlier studies for marker gene identification, we have considered a different set of machine learning classifiers to improve the accuracy rate from the analysis. Amongst all the six classification algorithms, J48 emerged as the best classifier, which could be used for differentiating healthy and diseased samples. SMO/SVM and Logit Boost further followed J48 to achieve the classification accuracy.