Vesicle trafficking plays an important role in cell division, establishment of cell polarity, and translation of environmental cues to developmental responses. However, the molecular mechanisms regulating vesicle trafficking remain poorly understood. Here, we report that the evolutionarily conserved caspase-related protease separase (EXTRA SPINDLE POLES [ESP]) is required for the establishment of cell polarity and cytokinesis in Arabidopsis thaliana. At the cellular level, separase colocalizes with microtubules and RabA2a (for RAS GENES FROM RAT BRAINA2a) GTPase-positive structures. Separase facilitates polar targeting of the auxin efflux carrier PIN-FORMED2 (PIN2) to the rootward side of the root cortex cells. Plants with the radially swollen4 (rsw4) allele with compromised separase activity, in addition to mitotic failure, display isotropic cell growth, perturbation of auxin gradient formation, slower gravitropic response in roots, and cytokinetic failure. Measurements of the dynamics of vesicle markers on the cell plate revealed an overall reduction of the delivery rates of KNOLLE and RabA2a GTPase in separase-deficient roots. Furthermore, dissociation of the clathrin light chain, a protein that plays major role in the formation of coated vesicles, was slower in rsw4 than in the control. Our results demonstrate that separase is a key regulator of vesicle trafficking, which is indispensable for cytokinesis and the establishment of cell polarity.
RNA can play multiple biological roles through use of its three-dimensional (3-D) structures. Recent advances in RNA structural biology have revealed that complex RNA 3D structures are assemblages of double-stranded helices with a variety of tertiary structural motifs. By employing RNA tertiary structural motifs together with the helices, we designed a novel class of self-folding RNA. In RNA composed of three helices (P1, P2, and P3), P1 interacts with P3 via a tetraloop-receptor interaction and P2 forms consecutive base-triples. Two designed RNAs of this class were prepared and their folding properties indicate that they form defined tertiary structures as designed. These RNAs may be used as modular units for constructing artificial ribozymes or nanometer-scale materials.
A high-fat diet (HFD) is one of the causes of hepatic steatosis. We previously demonstrated that Enterococcus faecalis FK-23 (FK-23), a type of lactic acid bacteria, exhibits an anti-obesity effect in mice fed a HFD. In the present study, we examined the effects of FK-23 on HFDinduced hepatic steatosis. Male C57BL/6 mice were divided into four groups and given one of four treatments: standard diet (SD); standard diet supplemented with FK-23 (SD þ FK); HFD; or HFD supplemented with FK-23 (HFD þ FK). For the administration of FK-23, the drinking water was supplemented with FK-23 at a concentration of 2 % (w/w). After 11 weeks, histological findings revealed hepatic steatosis in the liver of HFD-fed mice; however, this effect was attenuated by the administration of FK-23. The expression levels of genes involved in fatty acid oxidation in the liver tissue were significantly reduced in the HFD group compared with the SD group, but FK-23 supplementation tended to up-regulate the expression levels of these genes. Our findings show that the inhibitory effect of FK-23 against hepatic steatosis in HFD-fed mice can be explained by the prevention of fat accumulation in the liver through the modulation of the activities of genes involved in hepatic fatty acid oxidation.
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