Circular RNAs (circRNAs), formed by non-sequential back-splicing of pre-mRNA transcripts, are a widespread form of non-coding RNA in animal cells. However, it is unclear whether the majority of ...circRNAs represent splicing by-products without function or are produced in a regulated manner to carry out specific cellular functions. We show that hundreds of circRNAs are regulated during human epithelial-mesenchymal transition (EMT) and find that the production of over one-third of abundant circRNAs is dynamically regulated by the alternative splicing factor, Quaking (QKI), which itself is regulated during EMT. Furthermore, by modulating QKI levels, we show the effect on circRNA abundance is dependent on intronic QKI binding motifs. Critically, the addition of QKI motifs is sufficient to induce de novo circRNA formation from transcripts that are normally linearly spliced. These findings demonstrate circRNAs are both purposefully synthesized and regulated by cell-type specific mechanisms, suggesting they play specific biological roles in EMT.
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•Numerous circRNAs are regulated during epithelial to mesenchymal transition•Quaking (QKI) regulates circRNA formation during EMT•QKI binds to sites flanking circRNA-forming exons•Insertion of QKI binding sites into linear RNA can induce exon circularization
The RNA binding protein Quaking (QKI) promotes circRNA biogenesis during epithelial to mesenchymal transition, strongly arguing for their functions.
Total Synthesis of (+)-Rubriflordilactone A Goh, Shermin S.; Chaubet, Guilhem; Gockel, Birgit ...
Angewandte Chemie (International ed.),
October 19, 2015, Volume:
54, Issue:
43
Journal Article
Peer reviewed
Open access
Two enantioselective total syntheses of the nortriterpenoid natural product rubriflordilactone A are described, which use palladium‐ or cobalt‐catalyzed cyclizations to form the CDE rings, and ...converge on a late‐stage synthetic intermediate. These key processes are set up through the convergent coupling of a common diyne component with appropriate AB‐ring aldehydes, a strategy that sets the stage for the synthetic exploration of other members of this family of natural products.
Two in one: Two enantioselective total syntheses of the nortriterpenoid natural product rubriflordilactone A are described, which use palladium‐ or cobalt‐catalyzed cyclizations to converge on a late‐stage synthetic intermediate. These key processes are set up through the coupling of a common diyne component with appropriate AB‐ring aldehydes, a strategy that enables a broad exploration of this family of natural products, as well as synthetic analogues.
Summary Background With the advent of effective antiretroviral treatment, the life expectancy for people with HIV is now approaching that seen in the general population. Consequently, the relative ...importance of other traditionally non-AIDS-related morbidities has increased. We investigated trends over time in all-cause mortality and for specific causes of death in people with HIV from 1999 to 2011. Methods Individuals from the Data collection on Adverse events of anti-HIV Drugs (D:A:D) study were followed up from March, 1999, until death, loss to follow-up, or Feb 1, 2011, whichever occurred first. The D:A:D study is a collaboration of 11 cohort studies following HIV-1-positive individuals receiving care at 212 clinics in Europe, USA, and Australia. All fatal events were centrally validated at the D:A:D coordinating centre using coding causes of death in HIV (CoDe) methodology. We calculated relative rates using Poisson regression. Findings 3909 of the 49 731 D:A:D study participants died during the 308 719 person-years of follow-up (crude incidence mortality rate, 12·7 per 1000 person-years 95% CI 12·3–13·1). Leading underlying causes were: AIDS-related (1123 29% deaths), non-AIDS-defining cancers (590 15% deaths), liver disease (515 13% deaths), and cardiovascular disease (436 11% deaths). Rates of all-cause death per 1000 person-years decreased from 17·5 in 1999–2000 to 9·1 in 2009–11; we saw similar decreases in death rates per 1000 person-years over the same period for AIDS-related deaths (5·9 to 2·0), deaths from liver disease (2·7 to 0·9), and cardiovascular disease deaths (1·8 to 0·9). However, non-AIDS cancers increased slightly from 1·6 per 1000 person-years in 1999–2000 to 2·1 in 2009–11 (p=0·58). After adjustment for factors that changed over time, including CD4 cell count, we detected no decreases in AIDS-related death rates (relative rate for 2009–11 vs 1999–2000: 0·92 0·70–1·22). However, all-cause (0·72 0·61–0·83), liver disease (0·48 0·32–0·74), and cardiovascular disease (0·33 0·20–0·53) death rates still decreased over time. The percentage of all deaths that were AIDS-related (87/256 34% in 1999–2000 and 141/627 22% in 2009–11) and liver-related (40/256 16% in 1999–2000 and 64/627 10% in 2009–11) decreased over time, whereas non-AIDS cancers increased (24/256 9% in 1999–2000 to 142/627 23% in 2009–11). Interpretation Recent reductions in rates of AIDS-related deaths are linked with continued improvement in CD4 cell count. We hypothesise that the substantially reduced rates of liver disease and cardiovascular disease deaths over time could be explained by improved use of non-HIV-specific preventive interventions. Non-AIDS cancer is now the leading non-AIDS cause and without any evidence of improvement. Funding Oversight Committee for the Evaluation of Metabolic Complications of HAART, with representatives from academia, patient community, US Food and Drug Administration, European Medicines Agency and consortium of AbbVie, Boehringer Ingelheim, Bristol-Myers Squibb, Gilead Sciences, ViiV Healthcare, Merck, Pfizer, F Hoffmann-La Roche, and Janssen Pharmaceuticals.
OBJECTIVE:We studied the association of plasma albumin with cardiovascular disease (CVD) and explored potential mechanisms behind the association in the CGPS (Copenhagen General Population Study). We ...also performed a meta-analysis to summarize the association between plasma albumin and CVD in individuals without preexisting CVD.
APPROACH AND RESULTS:We included 100 520 individuals without prior CVD with 8247 incident CVD events developed during a median follow-up of 8.5 years. Rates of CVD outcomes were calculated using Cox regression and Fine and Gray competing-risks regression. The association of plasma albumin and CVD was approximately linear and confounder adjustment had little influence on the effect estimates, except for some attenuation after CRP (C-reactive protein) adjustment. In analyses according to subtypes of CVD events, the hazard ratios for each 10 g/L lower plasma albumin were 1.17 (95% CI, 1.08–1.28) for ischemic heart disease, 1.25 (95% CI, 1.09–1.43) for myocardial infarction, 1.37 (95% CI, 1.21–1.54) for any stroke, and 1.46 (95% CI, 1.28–1.68) for ischemic stroke. In the meta-analysis, we combined estimates from prospective and nested case-control studies investigating the association of plasma albumin with CVD. The meta-analysis included 14 studies with 150 652 individuals (12 studies reported events totaling 11 872). The risk ratio for a CVD event per 10 g/L lower plasma albumin was 1.96 (95% CI, 1.43–2.68) in previous studies and 1.85 (95% CI, 1.39–2.47) including our study with 57% weight in the meta-analysis. Exploratory analyses of the mechanism of the association indicated that it was probably not due to fatty acid binding but may be due to the regulation of plasma albumin by inflammation.
CONCLUSIONS:There is a robust, independent association of low plasma albumin with CVD, partly explained by plasma albumin as a negative acute-phase reactant.
CLINICAL TRIAL REGISTRATION:URLhttps://www.crd.york.ac.uk/prospero/display_record.php?RecordID=95796. Unique identifierCRD42018095796
Full details of the total synthesis of the Schisandraceae nortriterpenoid natural product rubriflordilactone A are reported. Palladium‐ and cobalt‐catalyzed polycyclizations were employed as key ...strategies to construct the central pentasubstituted arene from bromoendiyne and triyne precursors. This required the independent assembly of two AB ring aldehydes for combination with a common diyne component. A number of model systems were explored to investigate these two methodologies, and also to establish routes for the installation of the challenging benzopyran and butenolide rings.
Total terpenoids: The total synthesis of the Schisandraceae nortriterpene rubriflordilactone A is reported. Palladium‐ and cobalt‐catalyzed polycyclizations were employed as key strategies to construct the central arene D ring from bromoendiyne and triyne precursors. A number of model systems were explored to investigate these two methodologies, and also to establish routes for the installation of the challenging benzopyran and butenolide rings.
CCR4 is the sole receptor for the chemokines CCL22 and CCL17. Clinical studies of asthmatic airways have shown levels of both ligands and CCR4+ Th2 cells to be elevated, suggestive of a role in ...disease. Consequently, CCR4 has aroused much interest as a potential therapeutic target and an understanding of how its cell surface expression is regulated is highly desirable. To this end, receptor expression, receptor endocytosis, and chemotaxis were assessed using transfectants expressing CCR4, CCR4+ human T cell lines, and human Th2 cells polarized in vitro. CCL17 and CCL22 drove rapid endocytosis of CCR4 in a dose‐dependent manner. Replenishment at the cell surface was slow and sensitive to cycloheximide, suggestive of de novo synthesis of CCR4. Constitutive CCR4 endocytosis was also observed, with the internalized CCR4 found to be significantly degraded over a 6‐h incubation. Truncation of the CCR4 C‐terminus by 40 amino acids had no effect on cell surface expression, but resulted in significant impairment of ligand‐induced endocytosis. Consequently, migration to both CCL17 and CCL22 was significantly enhanced. In contrast, truncation of CCR4 did not impair constitutive endocytosis or degradation, suggesting the use of alternative receptor motifs in these processes. We conclude that CCR4 cell surface levels are tightly regulated, with a degradative fate for endocytosed receptor. We postulate that this strict control is desirable, given that Th2 cells recruited by CCR4 can induce the further expression of CCR4 ligands in a positive feedback loop, thereby enhancing allergic inflammation.
Both ligand‐induced and constitutive endocytosis of CCR4 leads to intracellular proteolysis, with differing requirements for the CCR4 C‐terminus.
Objectives
The shorter‐term overview from feces provides scope to investigate dietary fluctuations. We assess the correlation of stable isotopic fecal values with recorded seasonal diet of 10 adult ...chimpanzees (P. t. schweinfurthii) of the Kanyawara community (Kibale National Park, Uganda) and whether fecal nitrogen levels (%N) indicate a change in crude protein intake.
Materials and Methods
We recorded food eaten by each ape and collected both concurrent fecal samples (N = 115) and plant foods eaten by this community (N = 64). We compared fecal δ13C and δ15N values (also %N) with: (a) plant values; (b) feeding data; and (c) food‐items found macroscopically in the fecal samples. Interspecies and intraspecies differences in plant and fecal isotope values (and %N) as well as seasonality in diet were determined using parametric and nonparametric tests.
Results
No difference in plant δ13C and δ15N values was found at intraspecies or interspecies level. Fecal isotope values reflected a diet of C3 plants from evergreen forest vegetation. Seasonal differences in δ13C and δ15N corresponded with aspects of feeding and fecal macroscopic data, but only at community level. A change in crude protein intake was not indicated from %N content.
Discussion
This study further validates the use of staple isotope analyses of primate feces to provide a dietary overview, revealing seasonal differences at community level; however, conclusive results may be limited for individuals when using short sampling periods. Further study of variables that influence fecal %N content is also suggested to interpret crude protein intake.
The introduction of the Reduced height (Rht)-B1b and Rht-D1b semidwarfing genes led to impressive increases in wheat (Triticum aestivum) yields during the Green Revolution. The reduction in stem ...elongation in varieties containing these alleles is caused by a limited response to the phytohormone gibberellin (GA), resulting in improved resistance to stem lodging and yield benefits through an increase in grain number. Rht-B1 and Rht-D1 encode DELLA proteins, which act to repress GA-responsive growth, and their mutant alleles Rht-B1b and Rht-D1b are thought to confer dwarfism by producing more active forms of these growth repressors. While no semidwarfing alleles of Rht-A1 have been identified, we show that this gene is expressed at comparable levels to the other homeologs and represents a potential target for producing novel dwarfing alleles. In this study, we have characterized additional dwarfing mutations in Rht-B1 and Rht-D1. We show that the severe dwarfism conferred by Rht-B1c is caused by an intragenic insertion, which results in an in-frame 90-bp insertion in the transcript and a predicted 30-amino acid insertion within the highly conserved amino-terminal DELLA domain. In contrast, the extreme dwarfism of Rht-D1c is due to overexpression of the semidwarfing Rht-D1b allele, caused by an increase in gene copy number. We show also that the semidwarfing alleles Rht-B1d and Rht-B1e introduce premature stop codons within the amino-terminal coding region. Yeast two-hybrid assays indicate that these newly characterized mutations in Rht-B1 and Rht-D1 confer "GA-insensitive" dwarfism by producing DELLA proteins that do not bind the GA receptor GA INSENSITIVE DWARF1, potentially compromising their targeted degradation.
Pyruvate carboxylase (PC) is a biotin-containing enzyme that converts pyruvate to oxaloacetate. We have previously shown that PC is overexpressed in highly invasive cancer cell lines where it ...supports biosynthesis during rapid cell growth. Here, we show that miR-143-3p suppresses the expression of PC in MDA-MB-231 cells by targeting its conserved binding site in the 3′-untranslated region (UTR) of human PC mRNA. Incorporation of the PC 3′UTR into a luciferase reporter gene inhibited expression of luciferase by 50% while mutation of the miR-143-3p binding site abrogated this inhibitory effect in MDA-MB-231 cells but not in low aggressive MCF-7 cell line. Transfection of miR-143-3p mimic or overexpression of miR-143-3p using tetracycline-inducible system in MDA-MB-231 cells down-regulated expression of both endogenous PC mRNA and protein by 40% and 50% respectively, confirming the regulatory role of miR-143-3p in PC expression. Induction of miR-143-3p expression at low and high levels lowered proliferation, metabolic activity and migration of MDA-MB-231 cells, in a dose-dependent manner. Re-expression of PC in MDA-MB-231 cells which were induced to express miR-143-3p partially restored migration but not proliferation, indicating that miR-143-3p regulates proliferation and migration through multiple pathways.
•miR-143-3p directly targets PC via a conserved binding site in the 3′-UTR mRNA.•Transfection of luciferase construct containing 3′-UTR of hPC mRNA down-regulates.•Luciferase expression in MCF-7 but not MDA-MB-231 cells.•Overexpression of miR-143-3p in MDA-MB-231 cells lowers PC expression accompanied by reduced proliferation and migration.•Re-expression of PC in miR-143 expressing MDA-MB-231 cells partially restores migration but not proliferation.
Members of the miR‐200 family are critical gatekeepers of the epithelial state, restraining expression of pro‐mesenchymal genes that drive epithelial–mesenchymal transition (EMT) and contribute to ...metastatic cancer progression. Here, we show that miR‐200c and another epithelial‐enriched miRNA, miR‐375, exert widespread control of alternative splicing in cancer cells by suppressing the RNA‐binding protein Quaking (QKI). During EMT, QKI‐5 directly binds to and regulates hundreds of alternative splicing targets and exerts pleiotropic effects, such as increasing cell migration and invasion and restraining tumour growth, without appreciably affecting mRNA levels. QKI‐5 is both necessary and sufficient to direct EMT‐associated alternative splicing changes, and this splicing signature is broadly conserved across many epithelial‐derived cancer types. Importantly, several actin cytoskeleton‐associated genes are directly targeted by both QKI and miR‐200c, revealing coordinated control of alternative splicing and mRNA abundance during EMT. These findings demonstrate the existence of a miR‐200/miR‐375/QKI axis that impacts cancer‐associated epithelial cell plasticity through widespread control of alternative splicing.
Synopsis
miR‐200 and miR‐375 regulate the level of the RNA‐binding protein, Quaking (QKI), which orchestrates widespread control of alternative splicing during epithelial‐mesenchymal transition (EMT), thereby affecting multiple facets of cancer‐associated epithelial cell plasticity.
miR‐200c and miR‐375 control EMT‐associated alternative splicing by suppressing QKI.
QKI‐5 influences cell plasticity, invasion and tumour growth by modulating alternative splicing.
Actin cytoskeleton‐associated genes are targeted both by QKI and miR‐200c, revealing coordinated control of alternative splicing and mRNA abundance during EMT.
While miRNAs of the miR‐200 family are known to promote EMT and cancer progression via target mRNA repression, they exert a separate effect on epithelial cell plasticity by modulating alternative splicing signatures.
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