2859155
Bioassay-Guided Evolution of Glycosylated Macrolide Antibiotics in Escherichia coli
Macrolide antibiotics such as erythromycin are clinically important polyketide natural products. We have engineered a recombinant strain of Escherichia coli that produces small but measurable quantities of the bioactive macrolide 6-deoxyerythromycin D. Bioassay-guided evolution of this strain led to the identification of an antibiotic-overproducing mutation in the mycarose biosynthesis and transfer pathway that was detectable via a colony-based screening assay. This high-throughput assay was then used to evolve second-generation mutants capable of enhanced precursor-directed biosynthesis of macrolide antibiotics. The availability of a screen for macrolide biosynthesis in E. coli offers a fundamentally new approach in dissecting modular megasynthase mechanisms as well as engineering antibiotics with novel pharmacological properties.
1465194
Differential roles of human Dicer-binding proteins TRBP and PACT in small RNA processing
During RNA interference and related gene regulatory pathways, the endonuclease Dicer cleaves precursor RNA molecules to produce microRNAs (miRNAs) and short interfering RNAs (siRNAs). Human cells encode a single Dicer enzyme that can associate with two different double-stranded RNA (dsRNA)-binding proteins, protein activator of PKR (PACT) and trans-activation response RNA-binding protein (TRBP). However, the functional redundancy or differentiation of PACT and TRBP in miRNA and siRNA biogenesis is not well understood. Using a reconstituted system, we show here that PACT and TRBP have distinct effects on Dicer-mediated dsRNA processing. In particular, we found that PACT in complex with Dicer inhibits the processing of pre-siRNA substrates when compared with Dicer and a Dicer–TRBP complex. In addition, PACT and TRBP show non-redundant effects on the production of different-sized miRNAs (isomiRs), which in turn alter target-binding specificities. Experiments using chimeric versions of PACT and TRBP suggest that the two N-terminal RNA-binding domains of each protein confer the observed differences in dsRNA substrate recognition and processing behavior of Dicer–dsRNA-binding protein complexes. These results support the conclusion that in humans, Dicer-associated dsRNA-binding proteins are important regulatory factors that contribute both substrate and cleavage specificity during miRNA and siRNA production.
7970301
Dynamic Correlation between Intrahost HIV-1 Quasispecies Evolution and Disease Progression
Quantifying the dynamics of intrahost HIV-1 sequence evolution is one means of uncovering information about the interaction between HIV-1 and the host immune system. In the chronic phase of infection, common dynamics of sequence divergence and diversity have been reported. We developed an HIV-1 sequence evolution model that simulated the effects of mutation and fitness of sequence variants. The amount of evolution was described by the distance from the founder strain, and fitness was described by the number of offspring a parent sequence produces. Analysis of the model suggested that the previously observed saturation of divergence and decrease of diversity in later stages of infection can be explained by a decrease in the proportion of offspring that are mutants as the distance from the founder strain increases rather than due to an increase of viral fitness. The prediction of the model was examined by performing phylogenetic analysis to estimate the change in the rate of evolution during infection. In agreement with our modeling, in 13 out of 15 patients (followed for 3–12 years) we found that the rate of intrahost HIV-1 evolution was not constant but rather slowed down at a rate correlated with the rate of CD4+ T-cell decline. The correlation between the dynamics of the evolutionary rate and the rate of CD4+ T-cell decline, coupled with our HIV-1 sequence evolution model, explains previously conflicting observations of the relationships between the rate of HIV-1 quasispecies evolution and disease progression.
15313024
Aging and arterial stiffness.
Arterial walls stiffen with age. The most consistent and well-reported changes are luminal enlargement with wall thickening and a reduction of elastic properties at the level of large elastic arteries. Longstanding arterial pulsation in the central artery causes elastin fiber fatigue and fracture. Increased vascular calcification and endothelial dysfunction are also characteristic of arterial aging. These changes lead to increased pulse wave velocity, especially along central elastic arteries, and increases in systolic blood pressure and pulse pressure. Vascular aging is accelerated by coexisting cardiovascular risk factors, such as hypertension, metabolic syndrome and diabetes. Vascular aging is an independent risk factor for cardiovascular disease, from atherosclerosis to target organ damage, including coronary artery disease, stroke and heart failure. Various strategies, especially controlling hypertension, show benefit in preventing, delaying or attenuating vascular aging.
659605
Musical training effect on reading musical notation: evidence from event-related potentials.
Musical training enhances a range of non-musical cognitive functions, including visuospatial abilities. The aim of this study was to explore which event-related potential (ERP) components were enhanced or reduced as a result of musical training. Both electrophysiological and behavioral methods were used to compare musicians and non-musicians in the processing of pitch and duration when reading single musical notes. It was observed that in the early stage of note reading, the musician/non-musician differences emerged in the latency range of the N1 and N2. The N1 component was enhanced; in contrast, the N2 component was reduced in musicians. It is possible that musicians receive auditory meanings from visual music notations, so they therefore did not find it necessary to spend more resources on executing spatial attention than non-musicians do during pitch processing.
26020494
Molecular mechanisms of deguelin-induced apoptosis in transformed human bronchial epithelial cells.
Increasing evidence has demonstrated that the phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway plays an important role in cell proliferation, apoptosis, angiogenesis, adhesion, invasion, and migration, functions that are critical to cancer cell survival and metastasis. Increased expression of activated Akt has been observed in the early stages of tobacco-induced lung carcinogenesis. Moreover, blocking the PI3K/Akt pathway specifically inhibits the proliferation of non-small cell lung cancer (NSCLC) cells, indicating that the PI3K/Akt pathway is a potential target for chemoprevention and therapy in lung cancer. The aim of this work is to study the lung cancer chemopreventive potential of PI3K/Akt inhibitors using an in vitro lung carcinogenesis model. We found that genetic or pharmacologic approaches targeting the PI3K/Akt pathway inhibited the proliferation of premalignant and malignant human bronchial epithelial (HBE) cells. After screening several natural products to identify a potential lung cancer chemopreventive agent, we have found that deguelin, a rotenoid isolated from Mundulea sericea (Leguminosae), specifically inhibits the growth of transformed HBE and NSCLC cells by inducing cell-cycle arrest in the G2/M phase and apoptosis, with no detectable toxic effects on normal HBE cells, most likely due to the agent's ability to inhibit PI3K/Akt-mediated signaling pathways. The specific sensitivity of premalignant and malignant HBE and NSCLC cells to deguelin suggests that this drug could be clinically useful for chemoprevention in early-stage lung carcinogenesis and for therapy in confirmed lung cancer.
15275452
Chemopreventive effects of deguelin, a novel Akt inhibitor, on tobacco-induced lung tumorigenesis.
Tobacco carcinogens induce Akt activation and lung carcinogenesis. We previously demonstrated that deguelin, a natural plant product, specifically inhibits the proliferation of premalignant and malignant human bronchial epithelial cells by blocking Akt activation. To evaluate the ability of deguelin to block tobacco carcinogen-induced lung tumorigenesis, we evaluated the in vivo effects of deguelin on Akt activation and lung tumorigenesis in transgenic mice in which Akt expression was induced by tamoxifen and in 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone (NNK)/benzo(a)pyrene (BaP)-treated A/J mice. Deguelin suppressed Akt activation in vivo, as measured by immunohistochemistry and immunoblotting, and statistically significantly reduced NNK/BaP-induced lung tumor multiplicity, volume, and load in A/J mice, as monitored by microcomputed tomography image analysis, with no detectable toxicity. These results indicate that deguelin warrants consideration as a chemopreventive agent for early-stage lung carcinogenesis in a clinical lung cancer chemoprevention trial.