Evaluation of antioxidant properties in thirteen Fijian medicinal plants used in Alzheimer’s disease and related illness

Objective: The present study aims to evaluate antioxidant properties of decoction and ethanol extracts of Fijian medicinal plants using 2,2-diphenyl-1-picryl-hydrazyl (DPPH) scavenging assay. Method: Thirteen plant species belonging to Melastomataceae, Asteraceae, Apiaceae, Rutaceae, Goodeniaceae, Loganiaceae, Araliaceae, Solanaceae, Polygonaceae, Zingiberaceae and Anacardiaceae families were tested at 0.2 mg/mL, 0.4 mg/mL, 0.6 mg/mL, 0.8 mg/mL, 1.0 mg/mL, 1.5 mg/mL and 2.0 mg/mL concentrations for antioxidant properties. The antioxidant capabilities were compared with ascorbic acid standard. Results and Discussions: Among the decoction and ethanol extracts tested, all plants showed DPPH scavenging activity. The most potent antioxidant activity was seen in C. hirta with an IC50 value of 0.64 mg/mL. The activity of C. hirta was twofold more potent than the standard ascorbic acid (IC50 = 1.33 mg/mL) indicating that polar extracts of C. hirta contains compounds with relatively better antioxidant properties than ascorbic acid. Conclusion: The plant extracts used in this study were crude extracts, as it is envisaged that if the phytochemicals were isolated and purified from these plants, more prominent results could be expected. These plants could prove leads to safer and better candidates for the future selection of antioxidant. Key words: DPPH, Reactive Oxygen Species, Radical scavenging activity, Antioxidants, C. hirta, Ethanolic extracts, Decoction. Key Message: Polar extracts from medicinal plants have antioxidant properties apart from its traditional use. These plants can be investigated to understand the full potential of these plants

Dissection of Pol II Trigger Loop Function and Pol II Activity–Dependent Control of Start Site Selection In Vivo

Structural and biochemical studies have revealed the importance of a conserved, mobile domain of RNA Polymerase II (Pol II), the Trigger Loop (TL), in substrate selection and catalysis. The relative contributions of different residues within the TL to Pol II function and how Pol II activity defects correlate with gene expression alteration in vivo are unknown. Using Saccharomyces cerevisiae Pol II as a model, we uncover complex genetic relationships between mutated TL residues by combinatorial analysis of multiply substituted TL variants. We show that in vitro biochemical activity is highly predictive of in vivo transcription phenotypes, suggesting direct relationships between phenotypes and Pol II activity. Interestingly, while multiple TL residues function together to promote proper transcription, individual residues can be separated into distinct functional classes likely relevant to the TL mechanism. In vivo, Pol II activity defects disrupt regulation of the GTP-sensitive IMD2 gene, explaining sensitivities to GTP-production inhibitors, but contrasting with commonly cited models for this sensitivity in the literature. Our data provide support for an existing model whereby Pol II transcriptional activity provides a proxy for direct sensing of NTP levels in vivo leading to IMD2 activation. Finally, we connect Pol II activity to transcription start site selection in vivo, implicating the Pol II active site and transcription itself as a driver for start site scanning, contravening current models for this process

The Mub1/Ubr2 ubiquitin ligase complex regulates the conserved Dsn1 kinetochore protein

The kinetochore is the macromolecular complex that assembles onto centromeric DNA and orchestrates the segregation of duplicated chromosomes. More than 60 components make up the budding yeast kinetochore, including inner kinetochore proteins that bind to centromeric chromatin and outer proteins that directly interact with microtubules. However, little is known about how these components assemble into a functional kinetochore and whether there are quality control mechanisms that monitor kinetochore integrity. We previously developed a method to isolate kinetochore particles via purification of the conserved Dsn1 kinetochore protein. We find that the Mub1/Ubr2 ubiquitin ligase complex associates with kinetochore particles through the CENP-C(Mif2) protein. Although Mub1/Ubr2 are not stable kinetochore components in vivo, they regulate the levels of the conserved outer kinetochore protein Dsn1 via ubiquitylation. Strikingly, a deletion of Mub1/Ubr2 restores the levels and viability of a mutant Dsn1 protein, reminiscent of quality control systems that target aberrant proteins for degradation. Consistent with this, Mub1/Ubr2 help to maintain viability when kinetochores are defective. Together, our data identify a previously unknown regulatory mechanism for the conserved Dsn1 kinetochore protein. We propose that Mub1/Ubr2 are part of a quality control system that monitors kinetochore integrity, thus ensuring genomic stability

CTCF physically links cohesin to chromatin

Cohesin is required to prevent premature dissociation of sister chromatids after DNA replication. Although its role in chromatid cohesion is well established, the functional significance of cohesin's association with interphase chromatin is not clear. Using a quantitative proteomics approach, we show that the STAG1 (Scc3/SA1) subunit of cohesin interacts with the CCTC-binding factor CTCF bound to the c-myc insulator element. Both allele-specific binding of CTCF and Scc3/SA1 at the imprinted IGF2/H19 gene locus and our analyses of human DM1 alleles containing base substitutions at CTCF-binding motifs indicate that cohesin recruitment to chromosomal sites depends on the presence of CTCF. A large-scale genomic survey using ChIP-Chip demonstrates that Scc3/SA1 binding strongly correlates with the CTCF-binding site distribution in chromosomal arms. However, some chromosomal sites interact exclusively with CTCF, whereas others interact with Scc3/SA1 only. Furthermore, immunofluorescence microscopy and ChIP-Chip experiments demonstrate that CTCF associates with both centromeres and chromosomal arms during metaphase. These results link cohesin to gene regulatory functions and suggest an essential role for CTCF during sister chromatid cohesion. These results have implications for the functional role of cohesin subunits in the pathogenesis of Cornelia de Lange syndrome and Roberts syndromes