The human telomerase reverse transcriptase (hTERT) utilizes a template within the integral RNA subunit (hTR) to direct extension of telomeres. Telomerase exhibits repeat addition processivity (RAP) ...and must therefore translocate the nascent DNA product into a new RNA:DNA hybrid register to prime each round of telomere repeat synthesis. Here, we use single-molecule FRET and nuclease protection assays to monitor telomere DNA structure and dynamics during the telomerase catalytic cycle. DNA translocation during RAP proceeds through a previously uncharacterized kinetic substep during which the 3'-end of the DNA substrate base pairs downstream within the hTR template. The rate constant for DNA primer realignment reveals this step is not rate limiting for RAP, suggesting a second slow conformational change repositions the RNA:DNA hybrid into the telomerase active site and drives the extrusion of the 5'-end of the DNA primer out of the enzyme complex.
Abstract
Interconversions between nucleic acid structures play an important role in transcriptional and translational regulation and also in repair and recombination. These interconversions are ...frequently promoted by nucleic acid chaperone proteins. To monitor their kinetics, Förster resonance energy transfer (FRET) is widely exploited using ensemble fluorescence intensity measurements in pre-steady-state stopped-flow experiments. Such experiments only provide a weighted average of the emission of all species in solution and consume large quantities of materials. Herein, we lift these limitations by combining time-resolved fluorescence (TRF) with droplet microfluidics (DmF). We validate the innovative TRF-DmF approach by investigating the well characterized annealing of the HIV-1 (+)/(–) Primer Binding Sequences (PBS) promoted by a HIV-1 nucleocapsid peptide. Upon rapid mixing of the FRET-labelled (–)PBS with its complementary (+)PBS sequence inside microdroplets, the TRF-DmF set-up enables resolving the time evolution of sub-populations of reacting species and reveals an early intermediate with a ∼50 ps donor fluorescence lifetime never identified so far. TRF-DmF also favorably compares with single molecule experiments, as it offers an accurate control of concentrations with no upper limit, no need to graft one partner on a surface and no photobleaching issues.
The energy metabolism of essential microbial guilds in the biogeochemical sulfur cycle is based on a DsrAB-type dissimilatory (bi)sulfite reductase that either catalyzes the reduction of sulfite to ...sulfide during anaerobic respiration of sulfate, sulfite and organosulfonates, or acts in reverse during sulfur oxidation. Common use of dsrAB as a functional marker showed that dsrAB richness in many environments is dominated by novel sequence variants and collectively represents an extensive, largely uncharted sequence assemblage. Here, we established a comprehensive, manually curated dsrAB/DsrAB database and used it to categorize the known dsrAB diversity, reanalyze the evolutionary history of dsrAB and evaluate the coverage of published dsrAB-targeted primers. Based on a DsrAB consensus phylogeny, we introduce an operational classification system for environmental dsrAB sequences that integrates established taxonomic groups with operational taxonomic units (OTUs) at multiple phylogenetic levels, ranging from DsrAB enzyme families that reflect reductive or oxidative DsrAB types of bacterial or archaeal origin, superclusters, uncultured family-level lineages to species-level OTUs. Environmental dsrAB sequences constituted at least 13 stable family-level lineages without any cultivated representatives, suggesting that major taxa of sulfite/sulfate-reducing microorganisms have not yet been identified. Three of these uncultured lineages occur mainly in marine environments, while specific habitat preferences are not evident for members of the other 10 uncultured lineages. In summary, our publically available dsrAB/DsrAB database, the phylogenetic framework, the multilevel classification system and a set of recommended primers provide a necessary foundation for large-scale dsrAB ecology studies with next-generation sequencing methods.
•Detailed RNAcompete method for analyzing protein RNA-binding preferences.•RNAcompete utilized to analyze unconventional RNA-binding proteins, NUDT21 and CNBP.•RNAcompete-based motifs are consistent ...with previous experimental data.
RNA-binding proteins (RBPs) participate in diverse cellular processes and have important roles in human development and disease. The human genome, and that of many other eukaryotes, encodes hundreds of RBPs that contain canonical sequence-specific RNA-binding domains (RBDs) as well as numerous other unconventional RNA binding proteins (ucRBPs). ucRBPs physically associate with RNA but lack common RBDs. The degree to which these proteins bind RNA, in a sequence specific manner, is unknown. Here, we provide a detailed description of both the laboratory and data processing methods for RNAcompete, a method we have previously used to analyze the RNA binding preferences of hundreds of RBD-containing RBPs, from diverse eukaryotes. We also determine the RNA-binding preferences for two human ucRBPs, NUDT21 and CNBP, and use this analysis to exemplify the RNAcompete pipeline. The results of our RNAcompete experiments are consistent with independent RNA-binding data for these proteins and demonstrate the utility of RNAcompete for analyzing the growing repertoire of ucRBPs.
Fusarium head blight (FHB) is a major cereal disease caused by a complex of Fusarium species. These species vary in importance depending on climatic conditions, agronomic factors or host genotype. In ...addition, Fusarium species can release toxic secondary metabolites. These mycotoxins constitute a significant food safety concern as they have health implications in both humans and animals. The Fusarium species involved in FHB differ in their pathogenicity, ability to produce mycotoxins, and fungicide sensitivity. Accurate and exhaustive identification of Fusarium species in planta is therefore of great importance. In this study, using a new set of primers targeting the EF1α gene, the diversity of Fusarium species on cereals was evaluated using Illumina high-throughput sequencing. The PCR amplification parameters and bioinformatic pipeline were optimized with mock and artificially infected grain communities and further tested on 65 field samples. Fusarium species were retrieved from mock communities and good reproducibility between different runs or PCR cycle numbers was be observed. The method enabled the detection of as few as one single Fusarium-infected grain in 10,000. Up to 17 different Fusarium species were detected in field samples of barley, durum and soft wheat harvested in France. This new set of primers enables the assessment of Fusarium diversity by high-throughput sequencing on cereal samples. It provides a more exhaustive picture of the Fusarium community than the currently used techniques based on isolation or species-specific PCR detection. This new experimental approach may be used to show changes in the composition of the Fusarium complex or to detect the emergence of new Fusarium species as far as the EF1α sequence of these species show a sufficient amount of polymorphism in the portion of sequence analyzed. Information on the distribution and prevalence of the different Fusarium species in a given geographical area, and in response to various environmental factors, is of great interest for managing the disease and predicting mycotoxin contamination risks.
Ochratoxins are a group of mycotoxins that frequently occur as contaminants in agricultural commodities and foods, including dry-cured meats and cheeses. The fungus Aspergillus westerdijkiae is ...frequently isolated from aged foods and can produce ochratoxin A (OTA). However, individual strains of the fungus can have one of two OTA production phenotypes (chemotypes): OTA production and OTA nonproduction. Monitoring and early detection of OTA-producing fungi in food are the most effective strategies to manage OTA contamination. Therefore, we examined genome sequence data from five A. westerdijkiae strains isolated from the surface of cheese from southern Italy to identify genetic markers indicative of the twoOTA chemotypes. This analysis revealed a naturally occurring deletion of the OTA regulatory gene, otaR, in an OTA-nonproducing isolate.We used this information to design a polymerase chain reaction (PCR) method that could identify A. westerdijkiae and distinguish between the two OTA chemotypes. In this method, the PCR primers were complementary to conserved sequences flanking otaR and yielded different-sized amplicons from strains with the different chemotypes. The primers did not yield ota-region-specific amplicons from other OTA-producing species. Because the method is specific to A. westerdijkiae and can distinguish between the two OTA chemotypes, it has potential to significantly improve OTA monitoring programs.
•Two OTA chemotypes were identified among A. westerdijkiae isolates from cheese.•A natural deletion of otaR biosynthetic gene was identified in A. westerdijkiae.•A PCR assay targeting the otaR distinguishes between OTA producers and nonproducers.
Sugar beet cyst nematode Heterodera schachtii is a serious biotic limiting factor in sugar beet industry. In this study, 70 sugar beet accessions were screened against H. schachtii, of which 30 ...resistant and susceptible ones were subjected to polymorphic simple sequence repeat (SSR) marker analysis by seven Universal DNA Amplification (UDA) primer pairs randomly. The results showed a very high significant variation between resistant and susceptible sugar beet accessions in response to H. schachtii with 42 fold increase in nematode reproduction rate in susceptible ones. SSR primers produced 155 bands, out of which 91 ones showed polymorphism, indicating 59% genetic diversity. The highest polymorphic bands was of UDA013 primer with 17 and the lowest one in UDA010 with 10 bands. Average number of polymorphic bands per primer was 13 and per genotype 3.03 bands. The UDA015 had the highest polymorphic index content (PIC) of 80%, and the lowest 44% in UDA001 with the mean of 67%. Highest marker index (MI) was in UDA015 with 10.80, and lowest one 6.48 in UDA001, with the mean of 8.68. Cluster analysis using Numerical Taxonomy and Multivariate Analysis System (NTSYS) software, with UPGMA method based on Jacard's similarity matrix, divided the genotypes into 4 major clusters. The dendrogram was consistent with the clustering result of Principal Component Analysis (PCoA). The highest genetic similarity of 91% was between the genotypes 45 and 51, of which both were offspring of a half-brother and half-sister crossing. The results suggested novel sources of resistant to H. schachtii and that SSR marker is a reliable tool for revealing a high levels of polymorphism among the sugar beet genotypes.
•There is a high significant variation between sugar beet genotypes in response to cyst nematode, H. schachtii.•The most resistant sugar beet genotypes among the screened ones were the lines; 16 (SB32-HSF-5) and 5 (SB31-HSF-2).•SRR markers can be used efficiently to study the genetic diversity between resistant and susceptible sugar beet genotypes.•The genetic diversity is not always directly related to the resistance and or susceptibility of genotypes.
Studies of the human microbiome frequently omit characterization of fungal communities (the mycobiome), which limits our ability to investigate how fungal communities influence human health. The ...internal transcribed spacer 1 (ITS1) region of the eukaryotic ribosomal cluster has features allowing for wide taxonomic coverage and has been recognized as a suitable barcode region for species-level identification of fungal organisms. We developed custom ITS1 primer sets using iterative alignment refinement. Primer performance was evaluated using
testing and experimental testing of fungal cultures and human samples. Using an expanded novel reference database, SIS (18S-ITS1-5.8S), the newly designed primers showed an average
taxonomic coverage of 79.9% ± 7.1% compared to a coverage of 44.6% ± 13.2% using previously published primers (
= 0.05). The newly described primer sets recovered an average of 21,830 ± 225 fungal reads from fungal isolate culture samples, whereas the previously published primers had an average of 3,305 ± 1,621 reads (
= 0.03). Of note was an increase in the taxonomic coverage of the
genus, which went from a mean coverage of 59.5% ± 13% to 100.0% ± 0.0% (
= 0.0015) comparing the previously described primers to the new primers, respectively. The newly developed ITS1 primer sets significantly improve general taxonomic coverage of fungal communities infecting humans and increased read depth by an order of magnitude over the best-performing published primer set tested. The overall best-performing primer pair in terms of taxonomic coverage and read recovery, ITS1-30F/ITS1-217R, will aid in advancing research in the area of the human mycobiome.
The mycobiome constitutes all the fungal organisms within an environment or biological niche. The fungi are eukaryotes, are extremely heterogeneous, and include yeasts and molds that colonize humans as part of the microbiome. In addition, fungi can also infect humans and cause disease. Characterization of the bacterial component of the microbiome was revolutionized by 16S rRNA gene fragment amplification, next-generation sequencing technologies, and bioinformatics pipelines. Characterization of the mycobiome has often not been included in microbiome studies because of limitations in amplification systems. This report revisited the selection of PCR primers that amplify the fungal ITS1 region. We have identified primers with superior identification of fungi present in the database. We have compared the new primer sets against those previously used in the literature and show a significant improvement in read count and taxon identification. These primers should facilitate the study of fungi in human physiology and disease states.
Macaque monkey (Macaca fascicularis) meat (MM) has been reported to be consumed as meatball and soup products in Indonesia. MM is not allowed to be traded in Indonesia and is considered not halal ...meat; therefore, MM is not allowed to be consumed by Muslim communities. In this study, species-specific primer (SSP) targeting on mitochondrial displacement (D-loop) region coupled with real-time PCR assay was used to identify monkey meat in beef meatballs. The PCR product was also subjected to sequencing in order to ensure the adulteration practice of MM in beef meatballs. The primers were designed and subjected to in silico specificity test using BLAST. The used primers were: forward: 5’-TGACTCCCACCACATCCC-3’ and reverse: 5’-GTGTGGAGCTAGAATATTGAACCG-3’. Real-time PCR assay using SSP targeting on mt-D-loop primers was capable of identifying MM in meatball products, specifically with a detection limit of 0.0078 ng corresponding to 1% MM in beef meatballs. The developed method can be proposed as the standard method for detecting MM in food products intended for halal authentication analysis, provided that DNAs are available in food products.
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