Polymorphism of viral dsRNA in Xanthophyllomyces dendrorhous strains isolated from different geographic areas

<p>Abstract</p> <p>Background</p> <p>Strains of the astaxanthin producing yeast <it>Xanthophyllomyces dendrorhous </it>have been isolated from different cold regions around the earth, and the presence of double stranded RNA (dsRNA) elements was described in some isolates. This kind of viruses is widely distributed among yeasts and filamentous fungi and, although generally are cryptic in function, their studies have been a key factor in the knowledge of important fungi. In this work, the characterization and genetic relationships among dsRNA elements were determined in strains representatives of almost all regions of the earth where <it>X. dendrorhous </it>have been isolated.</p> <p>Results</p> <p>Almost all strains of <it>X. dendrorhous </it>analyzed carry one, two or four dsRNA elements, of molecular sizes in the range from 0.8 to 5.0 kb. Different dsRNA-patterns were observed in strains with different geographic origin, being L1 (5.0 kb) the common dsRNA element. By hybridization assays a high genomic polymorphism was observed among L1 dsRNAs of different <it>X. dendrorhous </it>strains. Contrary, hybridization was observed between L1 and L2 dsRNAs of strains from same or different regions, while the dsRNA elements of minor sizes (M, S1, and S2) present in several strains did not show hybridization with neither L1 or L2 dsRNAs. Along the growth curve of UCD 67-385 (harboring four dsRNAs) an increase of L2 relative to L1 dsRNA was observed, whiles the S1/L1 ratio remains constant, as well as the M/L1 ratio of Patagonian strain. Strains cured of S2 dsRNA were obtained by treatment with anisomycin, and comparison of its dsRNA contents with uncured strain, revealed an increase of L1 dsRNA while the L2 and S1 dsRNA remain unaltered.</p> <p>Conclusion</p> <p>The dsRNA elements of <it>X. dendrorhous </it>are highly variable in size and sequence, and the dsRNA pattern is specific to the geographic region of isolation. Each L1 and L2 dsRNA are viral elements able to self replicate and to coexist into a cell, and L1 and S2 dsRNAs elements could be part of a helper/satellite virus system in <it>X. dendrorhous</it>.</p

An Anillin-Ect2 Complex Stabilizes Central Spindle Microtubules at the Cortex during Cytokinesis

Cytokinesis occurs due to the RhoA-dependent ingression of an actomyosin ring. During anaphase, the Rho GEF (guanine nucleotide exchange factor) Ect2 is recruited to the central spindle via its interaction with MgcRacGAP/Cyk-4, and activates RhoA in the central plane of the cell. Ect2 also localizes to the cortex, where it has access to RhoA. The N-terminus of Ect2 binds to Cyk-4, and the C-terminus contains conserved DH (Dbl homologous) and PH (Pleckstrin Homology) domains with GEF activity. The PH domain is required for Ect2's cortical localization, but its molecular function is not known. In cultured human cells, we found that the PH domain interacts with anillin, a contractile ring protein that scaffolds actin and myosin and interacts with RhoA. The anillin-Ect2 interaction may require Ect2's association with lipids, since a novel mutation in the PH domain, which disrupts phospholipid association, weakens their interaction. An anillin-RacGAP50C (homologue of Cyk-4) complex was previously described in Drosophila, which may crosslink the central spindle to the cortex to stabilize the position of the contractile ring. Our data supports an analogous function for the anillin-Ect2 complex in human cells and one hypothesis is that this complex has functionally replaced the Drosophila anillin-RacGAP50C complex. Complexes between central spindle proteins and cortical proteins could regulate the position of the contractile ring by stabilizing microtubule-cortical interactions at the division plane to ensure the generation of active RhoA in a discrete zone

Synthesis, spectroscopic characterization and structural investigation of new charge-transfer complexes of piroxicam with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and chloranilic acid: Experimental and theoretical studies

###EgeUn###Charge transfer (CT) complexes have great scientific importance because they include wide applications in different fields, one of the most essential of these applications is to determine the activity of pharmacological compounds. CT complexes between the donor piroxicam and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and chloranilic acid (ChA) as electron acceptors have been studied and characterized both experimentally and theoretically. Herewith we aimed to determine the stability of the expected structure of the formed piroxicam complexes for the first time. Several analytical tools (FTIR, NMR, mass spectrometry, UV-Visible spectroscopy and conductometric analysis) were applied to characterize these complexes. The stoichiometry of the examined complexes was assessed using Job’s method and Benesi-Hildebrand equation, and a molar ratio of 1:1 between the donor and acceptors were resulted from these complexes. The physical parameters of the formed CT-complexes were determined by calculations of formation constant, molar absorptivity, oscillator strength, dipole moment, ionization potential, CT energy, resonance energy, dissociation energy, and standard free energy of complexation. In addition, the UV-Vis spectra and CT transition properties of these complexes were computationally determined with DFT and TD-DFT methods. The results confirmed that these complexes are CT complexes. The current study shows that the complexes formed are stable and can be used for the determination of piroxicam in pharmaceutical form. © 2019 by American Scientific Publishers All rights reserved.Deanship of Scientific Research, King Saud UniversityAcknowledgment: The authors express their gratitude to the Deanship of Scientific Research at King Saud University for funding this work through the Research Group Project No. RGP-1438-045. The numerical calculations reported in this paper were fully/partially performed at TUBITAK ULAKBIM, High Performance and Grid Computing Center (TRUBA resources). -