The presence of a G-quadruplex prone sequence upstream of a minimal promoter increases transcriptional activity in the yeast Saccharomyces cerevisiae.

Non-canonical secondary structures in DNA are increasingly being revealed as critical players in DNA metabolism, including modulating the accessibility and activity of promoters. These structures comprise the so-called G-quadruplexes (G4s) that are formed from sequences rich in guanine bases. Using a well-defined transcriptional reporter system, we sought to systematically investigate the impact of the presence of G4 structures on transcription in yeast Saccharomyces cerevisiae. To this aim, different G4 prone sequences were modeled to vary the chance of intramolecular G4 formation, analyzed in vitro by Thioflavin T binding test and circular dichroism and then placed at the yeast ADE2 locus on chromosome XV, downstream and adjacent to a P53 response element (RE) and upstream from a minimal CYC1 promoter and Luciferase 1 (LUC1) reporter gene in isogenic strains. While the minimal CYC1 promoter provides basal reporter activity, the P53 RE enables LUC1 transactivation under the control of P53 family proteins expressed under the inducible GAL1 promoter. Thus, the impact of the different G4 prone sequences on both basal and P53 family protein-dependent expression was measured after shifting cells onto galactose containing medium. The results showed that the presence of G4 prone sequences upstream of a yeast minimal promoter increased its basal activity proportionally to their potential to form intramolecular G4 structures; consequently, this feature, when present near the target binding site of P53 family transcription factors, can be exploited to regulate the transcriptional activity of P53, P63 and P73 proteins.

Limonium duriusculum (de Girard) Kuntze Exhibits Anti-inflammatory Effect Via NF-κ B Pathway Modulation

HIGHLIGHTS L. duriusculum n-BuOH extract reduces inflammatory responses both in vitro and in vivo. L. duriusculum n-BuOH extract inhibits NF-κB-dependent transcriptional responses. L. duriusculum n-BuOH extract decreases the expression of TNF-α and IL-6 genes.

Abstract Limonium duriusculum is used in folk medicine to treat inflammatory disorders and has gained attention due to its richness in apigenin. The present investigation was performed to evaluate and confirm its anti-inflammatory properties, in cell lines and animal models. The potential anti-inflammatory properties of n-butanol (n-BuOH) extract of L. duriusculum (BEL) and isolated apigenins were examined on NF-κB transcriptional activity in TNFα- or LPS-stimulated cells, and on in vivo acute inflammatory models (carrageenan induced paw edema and peritonitis). BEL treatment was able to inhibit the activity of an NF-κB reporter gene in HCT116 cells both in the absence and in the presence of exogenous TNFα, used as NF-κB pathway inducer. This anti-inflammatory effect was even more potent compared to Apigenin (APG1) and was confirmed using monocyte-derived THP-1 cells treated with LPS to stimulate NF-κB-dependent transcription of IL-6 and TNFα mRNAs. Apigenin7-O-β-(6''-methylglucuronide) (APG2) was instead inactive both in HCT116 and THP-1 cells. BEL (oral, 200 mg/kg) led to paw swelling inhibition, vascular permeability and peritoneal leukocyte and PN migration diminution. Apigenins (intraperitoneal, APG1, APG2: 20 mg/kg) also evoked a significant anti-edema effect, early vascular permeability and leukocyte influx reduction. Collectively, this study demonstrates for the first time the effectiveness of L. duriusculum to inhibit NF-κB-dependent transcriptional responses in HCT116 and THP-1 cells. In vivo studies also established that L. duriusculum possesses a potential anti-inflammatory effect, confirm its traditional, empirical use, that could be attributed to its richness in apigenin.