Structural polymorphism exhibited by a homopurine.homopyrimidine sequence found at the right end of human c-jun protooncogene

Homopurine·homopyrimidine (Pu·Py) tracts are likely to play important biological role in eukaryotes. Using circular dichroism, UV-thermal denaturation and gel electrophoresis, we have analyzed the structural polymorphism of a 21-bp Pu·Py DNA segment within human c-jun protooncogene 3′-region, a potential target for triplex formation. Results show that below physiological pH and in the presence of Na⁺/K⁺ with Mg²⁺ the duplex is destabilized/disproportionated, resulting in strand mediated structural transitions to the self-associated structures of G- and C-rich strands separately, identified as G-quadruplex and i-motif species. A significant differential behavior of the monovalent cations was observed, accordingly the presence of Na⁺ in acidic as well as neutral pH facilitated the duplex formation, while K⁺ favored the formation of self-associated structures. In Na⁺ and Mg²⁺, under acidic and neutral pH conditions, the duplex displayed triphasic and biphasic melting profiles, respectively. This self-association property of oligonucleotides might limit their use as duplex targets in triplex formation. Study is also relevant for understanding structural and biological properties of DNA sequence containing homopurine tracts.     

Enhancing the biocatalytic potential of carbonyl reductase of Candida viswanathii using aqueous-organic solvent system

In the present work, the toxic effect of various solvents with different Log P values was studied on the whole cells of Candida viswanathii. Experiments showed that the lower concentrations of some solvent increased both the activity retention and enzyme activity as compared to the control while this was not the case with higher concentrations of the same solvents. The model compound taken in the present study was 1-acetophenone. The percentage conversion improved from 76 to 94%. Addition of 2-propanol increased the substrate tolerance, giving the conversion of 90% compared to 9% in control at a substrate concentration of 70 mM in 1h. The operational stability increased at higher temperatures with the addition of 2-propanol in the reaction mixture with good conversion (90%) and enantiomeric excess (>99%) at 45 degrees C and 50 degrees C. The effect was also found to be prominent in other tested substrates. In order to further stabilize the cells for long term use in higher concentration of organic solvents, the cells were further immobilized, and were found to have higher activity retention than that of free cells.     

Vaccinia virus l1 protein is required for cell entry and membrane fusion

Genetic and biochemical studies have provided evidence for an entry/fusion complex (EFC) comprised of at least eight viral proteins (A16, A21, A28, G3, G9, H2, J5, and L5) that together with an associated protein (F9) participates in entry of vaccinia virus (VACV) into cells. The genes encoding these proteins are conserved in all poxviruses, are expressed late in infection, and are components of the mature virion membrane but are not required for viral morphogenesis. In addition, all but one component has intramolecular disulfides that are formed by the poxvirus cytoplasmic redox system. The L1 protein has each of the characteristics enumerated above except that it has been reported to be essential for virus assembly. To further investigate the role of L1, we constructed a recombinant VACV (vL1Ri) that inducibly expresses L1. In the absence of inducer, L1 synthesis was repressed and vL1Ri was unable to form plaques or produce infectious progeny. Unexpectedly, assembly and morphogenesis appeared normal and the noninfectious virus particles were indistinguishable from wild-type VACV as determined by transmission electron microscopy and analysis of the component polypeptides. Notably, the L1-deficient virions were able to attach to cells but the cores failed to penetrate into the cytoplasm. In addition, cells infected with vL1Ri in the absence of inducer did not form syncytia following brief low-pH treatment even though extracellular virus was produced. Coimmunoprecipitation experiments demonstrated that L1 interacted with the EFC and indirectly with F9, suggesting that L1 is an additional component of the viral entry apparatus.     

Collagen fibril D-period may change as a function of strain and location in ligament

The purpose of this study was to determine if the characteristic banding pattern (D-period) of collagen fibrils from rabbit medial collateral ligaments changes as a function of gross ligament strain and, if so, whether the changes are location dependent (insertion versus midsubstance). Femur–medial collateral ligament–tibia complexes were strained to 0, 8, or 12% and immediately chemically fixed in situ. Samples were taken from the medial collateral ligament midsubstance and bony insertions, and prepared for and observed under a transmission electron microscope. D-period length was measured and found to increase (albeit not significantly so, p=0.1) as a function of gross strain for samples obtained from the insertion sites but not for samples obtained from the ligament midsubstance. Results suggested that ligament strains are inhomogeneous at the ultrastructural level.     

Molecular docking analysis of FDA approved drugs with the glycoprotein from Junin and Machupo viruses

Arenaviruses, Junin and Machupo are pathogenic viruses in regions of South America including Argentina and Bolivia causing haemorrhagic fever among humans. They have been transmitted to humans through mouse causing chronic illness with high mortality. Therefore, it is of interest to acquittance the molecular docking analysis data of FDA approved drugs with the glycoprotein from Junin and Machupo viruses for consideration in drug discovery. Thus, we report the optimal binding features of MK-3207 and Dihydro ergotamine with the protein target for further validation and consideration.     

MicroRNA-34a causes ceramide accumulation and effects insulin signaling pathway by targeting ceramide kinase (CERK) in aging skeletal muscle

Aging skeletal muscle shows perturbations in metabolic functions. MicroRNAs have been shown to play a critical role in aging and metabolic functions of skeletal muscle. MicroRNA-34a (miR-34a) is implicated in the brain and cardiac aging, however, its role in aging muscle is unclear. We analyzed levels of miR-34a, ceramide kinase (CERK) and other insulin signaling molecules in skeletal muscle from old mice. In addition to in vivo model, levels of these molecules were also analyzed in myoblast derived from insulin resistant (IR) humans and C2C12 myoblasts overexpressing mir-34a. Our results show that miR-34a is elevated in the muscles of 2-year-old mice and in the myoblasts of IR humans. Overexpression of miR-34a in C2C12 myoblasts leads to alterations in the insulin signaling pathway, which were rescued by its antagonism. Our analyses revealed that miR-34a targets CERK resulting in ceramide accumulation, activation of PP2A and the pJNK pathway in muscle and C2C12 myoblasts. Also, myostatin (Mstn) levels were increased in 2-year-old mouse muscle and Mstn treatment upregulated miR-34a in C2C12 myoblasts. In addition, miR-34a expression and ceramide levels did not increase during aging in Mstn^−/− mice muscle. In summary, we, therefore, propose that Mstn levels increase in aging muscle and upregulate miR-34a, which inhibits CERK resulting in increased ceramide levels. This ceramide accumulation activates PP2A and pJNK causing hypophosphorylation of AKT and hyperphosphorylation of IRS1 (Ser307), respectively, impairing insulin signaling pathway and eventually inhibiting the sarcolemma localization of GLUT4. These changes would result in reduced glucose uptake and insulin resistance. This study is the first to explain the phenomenon of ceramide accrual and impairment of insulin signaling pathway in aging muscle through a miR-34a based mechanism. In conclusion, our results suggest that Mstn and miR-34a antagonism can help ameliorate ceramide accumulation and loss of insulin sensitivity in aging skeletal muscle.