MicroRNAs can regulate human APP levels

A number of studies have shown that increased APP levels, resulting from either a genomic locus duplication or alteration in APP regulatory sequences, can lead to development of early-onset dementias, including Alzheimer's disease (AD). Therefore, understanding how APP levels are regulated could provide valuable insight into the genetic basis of AD and illuminate novel therapeutic avenues for AD. Here we test the hypothesis that APP protein levels can be regulated by miRNAs, evolutionarily conserved small noncoding RNA molecules that play an important role in regulating gene expression. Utilizing human cell lines, we demonstrate that miRNAs hsa-mir-106a and hsa-mir-520c bind to their predicted target sequences in the APP 3'UTR and negatively regulate reporter gene expression. Over-expression of these miRNAs, but not control miRNAs, results in translational repression of APP mRNA and significantly reduces APP protein levels. These results are the first to demonstrate that levels of human APP can be regulated by miRNAs.     

Platelet endothelial cell adhesion molecule 1 (PECAM-1) and its interactions with glycosaminoglycans: 1. Molecular modeling studies

Platelet endothelial cell adhesion molecule 1 (PECAM-1) has many functions, including its roles in leukocyte extravasation as part of the inflammatory response and in the maintenance of vascular integrity through its contribution to endothelial cell-cell adhesion. PECAM-1 has been shown to mediate cell-cell adhesion through homophilic binding events that involve interactions between domain 1 of PECAM-1 molecules on adjacent cells. However, various heterophilic ligands of PECAM-1 have also been proposed. The possible interaction of PECAM-1 with glycosaminoglycans (GAGs) is the focus of this study. The three-dimensional structure of the extracellular immunoglobulin (Ig) domains of PECAM-1 were constructed using homology modeling and threading methods. Potential heparin/heparan sulfate-binding sites were predicted on the basis of their amino acid consensus sequences and a comparison with known structures of sulfate-binding proteins. Heparin and other GAG fragments have been docked to investigate the structural determinants of their protein-binding specificity and selectivity. The modeling has predicted two regions in PECAM-1 that appear to bind heparin oligosaccharides. A high-affinity binding site was located in Ig domains 2 and 3, and evidence for a low-affinity site in Ig domains 5 and 6 was obtained. These GAG-binding regions were distinct from regions involved in PECAM-1 homophilic interactions.     

36 Identification and characterization of small subunit ribosomal intermediates

Bacterial ribosome biogenesis is poorly understood especially in terms of the role of ribosomal RNA (rRNA) maturation in vivo. A major problem in addressing these questions are asynchronous biogenesis, a large population of mature particles and the lack of techniques to isolated in vivo formed ribosome biogenesis intermediates. Our group has taken multiple approaches to allow study of ribosome biogenesis in Escherichia coli. We have used genetic manipulation to discover that for specific biogenesis factors, there is a delicate balance that is necessary for viability. Additionally, we have pioneered an affinity purification approach to allow for isolation of in vivo formed intermediates. Data will be present on our findings for the role of rRNA maturation in biogenesis, subsequent ribosome function, and cell viability. Our findings may result in identification of novel targets for antimicrobial development.     

Aurora kinase Ipl1 facilitates bilobed distribution of clustered kinetochores to ensure error‐free chromosome segregation in Candida albicans

Candida albicans, an ascomycete, has an ability to switch to diverse morphological forms. While C. albicans is predominatly diploid, it can tolerate aneuploidy as a survival strategy under stress. Aurora kinase B homolog Ipl1 is a critical ploidy regulator that controls microtubule dynamics and chromosome segregation in Saccharomyces cerevisiae. In this study, we show that Ipl1 in C. albicans has a longer activation loop than that of the well‐studied ascomycete S. cerevisiae. Ipl1 localizes to the kinetochores during the G1/S phase and associates with the spindle during mitosis. Ipl1 regulates cell morphogenesis and is required for cell viability. Ipl1 monitors microtubule dynamics which is mediated by separation of spindle pole bodies. While Ipl1 is dispensable for maintaining structural integrity and clustering of kinetochores in C. albicans, it is required for the maintenance of bilobed distribution of clustered kinetochores along the mitotic spindle. Depletion of Ipl1 results in erroneous kinetochore‐microtubule attachments leading to aneuploidy due to which the organism can survive better in the presence of fluconazole. Taking together, we suggest that Ipl1 spatiotemporally ensures bilobed kinetochore distribution to facilitate bipolar spindle assembly crucial for ploidy maintenance in C. albicans.     

DrRecQ regulates guanine quadruplex DNA structure dynamics and its impact on radioresistance in Deinococcus radiodurans

The GC‐rich genome of Deinococcus radiodurans contains a very high density of putative guanine quadruplex (G4) DNA motifs and its RecQ (drRecQ) was earlier characterized as a 3′→5′ dsDNA helicase. We saw that N‐Methyl mesoporphyrin IX (NMM), a G4 DNA binding drug affected normal growth as well as the gamma radiation resistance of the wild‐type bacterium. Interestingly, NMM treatment and recQ deletion showed additive effect on normal growth but there was no effect of NMM on gamma radiation resistance of recQ mutant. The recombinant drRecQ showed ~400 times higher affinity to G4 DNA (K_d = 11.74 ± 1.77 nM) as compared to dsDNA (K_d = 4.88 ± 1.30 µM). drRecQ showed ATP independent helicase function on G4 DNA, which was higher than ATP‐dependent helicase activity on dsDNA. Unlike wild‐type cells that sparingly stained for G4 structure with Thioflavin T (ThT), recQ mutant showed very high‐density of ThT fluorescence foci on DNA indicating an important role of drRecQ in regulation of G4 DNA structure dynamics in vivo. These results together suggested that drRecQ is an ATP independent G4 DNA helicase that plays an important role in the regulation of G4 DNA structure dynamics and its impact on radioresistance in D. radiodurans.     

Xanthomonas hortorum – beyond gardens: Current taxonomy,genomics, and virulence repertoires

TaxonomyBacteria; Phylum Proteobacteria; Class Gammaproteobacteria; Order Lysobacterales (earlier synonym of Xanthomonadales); Family Lysobacteraceae (earlier synonym of Xanthomonadaceae); Genus Xanthomonas; Species X. hortorum; Pathovars: pv. carotae, pv. vitians, pv. hederae, pv. pelargonii, pv. taraxaci, pv. cynarae, and pv. gardneri.Host range Xanthomonas hortorum affects agricultural crops, and horticultural and wild plants. Tomato, carrot, artichoke, lettuce, pelargonium, ivy, and dandelion were originally described as the main natural hosts of the seven separate pathovars. Artificial inoculation experiments also revealed other hosts. The natural and experimental host ranges are expected to be broader than initially assumed. Additionally, several strains, yet to be assigned to a pathovar within X. hortorum, cause diseases on several other plant species such as peony, sweet wormwood, lavender, and oak‐leaf hydrangea.Epidemiology and control X. hortorum pathovars are mainly disseminated by infected seeds (e.g., X. hortorum pvs carotae and vitians) or cuttings (e.g., X. hortorum pv. pelargonii) and can be further dispersed by wind and rain, or mechanically transferred during planting and cultivation. Global trade of plants, seeds, and other propagating material constitutes a major pathway for their introduction and spread into new geographical areas. The propagules of some pathovars (e.g., X. horturum pv. pelargonii) are spread by insect vectors, while those of others can survive in crop residues and soils, and overwinter until the following growing season (e.g., X. hortorum pvs vitians and carotae). Control measures against X. hortorum pathovars are varied and include exclusion strategies (i.e., by using certification programmes and quarantine regulations) to multiple agricultural practices such as the application of phytosanitary products. Copper‐based compounds against X. hortorum are used, but the emergence of copper‐tolerant strains represents a major threat for their effective management. With the current lack of efficient chemical or biological disease management strategies, host resistance appears promising, but is not without challenges. The intrastrain genetic variability within the same pathovar poses a challenge for breeding cultivars with durable resistance.Useful websites https://gd.eppo.int/taxon/XANTGA, https://gd.eppo.int/taxon/XANTCR, https://gd.eppo.int/taxon/XANTPE, https://www.euroxanth.eu, http://www.xanthomonas.org, http://www.xanthomonas.org/dokuwiki     

Influence of Zinc on Calcium-Dependent Signal Transduction Pathways During Aluminium-Induced Neurodegeneration

Metals perform important functions in the normal physiological system, and alterations in their levels may lead to a number of diseases. Aluminium (Al) has been implicated as a major risk factor, which is linked to several neurodegenerative diseases including Alzheimer’s disease and Parkinson’s disease. On the other hand, zinc (Zn) is considered as a neuromodulator and an essential dietary element that regulates a number of biological activities in our body. The aim of the present study was to investigate the effects of Zn supplementation, if any, in ameliorating the changes induced by Al on calcium signalling pathway. Male Sprague Dawley rats weighing 140–160 g were divided into four different groups viz.: normal control, aluminium treated (100 mg/kg b.wt./day via oral gavage), zinc treated (227 mg/l in drinking water) and combined aluminium and zinc treated. All the treatments were carried out for a total duration of 8 weeks. Al treatment decreased the Ca²⁺ ATPase activity whereas increased the levels of 3′, 5′-cyclic adenosine monophosphate, intracellular calcium and total calcium content in both the cerebrum and cerebellum, which, however, were modulated upon Zn supplementation. Al treatment exhibited a significant elevation in the protein expressions of phospholipase C, inositol triphosphate and protein kinase A but decreased the expression of protein kinase C, which, however, was reversed upon Zn co-treatment. Al treatment also revealed alterations in neurohistoarchitecture in the form of calcium deposits, which were improved upon zinc co-administration. The present study, therefore, suggests that zinc regulates the intracellular calcium signalling pathway during aluminium-induced neurodegeneration.