Sequence Entries Research Articles

IntronDB: a database for eukaryotic intron features.

The rate and extent of unbalanced eukaryotic intron changes exhibit dynamic patterns for different lineages of species or certain functional groups of genes with varied spatio-temporal expression modes affected by selective pressure. To date, only a few key conserved splicing signals or regulatory elements have been identified in introns and little is known about the remaining intronic regions. To trace the evolutionary trajectory of spliceosomal introns from available genomes under a unified framework, we present IntronDB, which catalogs ∼50000000 introns from over 1000 genomes spanning the major eukaryotic clades in the tree of life. Based on the position of introns relative to coding regions, it categorizes introns into three groups, such as 5'UTR, CDS and 3'UTR and subsequently divides CDS introns into three categories, such as phase 0, phase 1 and phase 2. It provides the quality evaluation for each sequence entry and characterizes the intronic parameters including number, size, sequence composition and positioning information as well as the features for exons and genes, making possible the comparisons between introns and exons. It reports the dinucleotides around the intron boundary and displays the consensus sequence features for all introns, small introns and large introns for each genome. By incorporating the taxonomic assignment of genomes, it performs high-level or genome-wide statistical analysis for single feature and coupled features both in a single genome and across multiple genomes. It offers functionalities to browse the data from representative protein-coding transcripts and download the data from all transcripts from protein-coding genes. http://www.nextgenbioinformatics.org/IntronDB. Supplementary data are available at Bioinformatics online.

G4Hunter web application: a web server for G-quadruplex prediction.

MotivationExpanding research highlights the importance of guanine quadruplex structures. Therefore, easy-accessible tools for quadruplex analyses in DNA and RNA molecules are important for the scientific community.ResultsWe developed a web version of the G4Hunter application. This new web-based server is a platform-independent and user-friendly application for quadruplex analyses. It allows retrieval of gene/nucleotide sequence entries from NCBI databases and provides complete characterization of localization and quadruplex propensity of quadruplex-forming sequences. The G4Hunter web application includes an interactive graphical data representation with many useful options including visualization, sorting, data storage and export.Availability and implementationG4Hunter web application can be accessed at: http://bioinformatics.ibp.cz.Supplementary information Supplementary data are available at Bioinformatics online.

A next generation sequencing approach for targeted Varroa destructor (Acari: Varroidae) mitochondrial DNA analysis based on honey derived environmental DNA.

Honey contains DNA from many different organisms that are part of hive micro-environmental niches and honey bee pathospheres. In this study, we recovered and sequenced mite mitochondrial DNA (mtDNA) from honey from different locations around the world (Europe, Asia, Africa, North and South America). DNA extracted from 17 honey samples was amplified with eight primer pairs targeting three mite mtDNA genes, obtaining 88 amplicons that were sequenced with an Ion Torrent sequencing platform. A bioinformatic pipeline compared produced reads with Varroa spp. mtDNA sequence entries available in GenBank and assigned them to different mitotypes. In all honey samples, the highest percentage of reads was attributed to the K1 lineage, including a few variants derived from it, in addition to J1 reads observed in the two South American samples and C1-1 reads obtained from the Chinese honey. This study opens new possibilities to analyse mite lineages and variants and monitor their geographical and temporal distribution, simplifying surveillance against this damaging honey bee parasite.

A reference cytochrome c oxidase subunit I database curated for hierarchical classification of arthropod metabarcoding data.

Metabarcoding is a popular application which warrants continued methods optimization. To maximize barcoding inferences, hierarchy-based sequence classification methods are increasingly common. We present methods for the construction and curation of a database designed for hierarchical classification of a 157 bp barcoding region of the arthropod cytochrome c oxidase subunit I (COI) locus. We produced a comprehensive arthropod COI amplicon dataset including annotated arthropod COI sequences and COI sequences extracted from arthropod whole mitochondrion genomes, the latter of which provided the only source of representation for Zoraptera, Callipodida and Holothyrida. The database contains extracted sequences of the target amplicon from all major arthropod clades, including all insect orders, all arthropod classes and Onychophora, Tardigrada and Mollusca outgroups. During curation, we extracted the COI region of interest from approximately 81 percent of the input sequences, corresponding to 73 percent of the genus-level diversity found in the input data. Further, our analysis revealed a high degree of sequence redundancy within the NCBI nucleotide database, with a mean of approximately 11 sequence entries per species in the input data. The curated, low-redundancy database is included in the Metaxa2 sequence classification software (http://microbiology.se/software/metaxa2/). Using this database with the Metaxa2 classifier, we performed a cross-validation analysis to characterize the relationship between the Metaxa2 reliability score, an estimate of classification confidence, and classification error probability. We used this analysis to select a reliability score threshold which minimized error. We then estimated classification sensitivity, false discovery rate and overclassification, the propensity to classify sequences from taxa not represented in the reference database. Our work will help researchers design and evaluate classification databases and conduct metabarcoding on arthropods and alternate taxa.

Protocol Sequences With Carrier Sensing for Wireless Sensor Networks

Protocol sequences are deterministic binary sequences of a common period, which enjoy some special Hamming cross-correlation property by design. In contrast to random or contention-based medium access control schemes, a protocol sequence-based scheme can serve to provide at least a certain number of contention-free packet transmissions within a bounded delay for each asynchronous user in a feedback-free multiple access system. However, all protocol sequence-based schemes in the literature require that all sequence entries are mapped to slots with the same time duration, which produces a relatively low channel utilization. To overcome this inefficiency that is undesirable in delay-constrained wireless sensor networks, building on the idea of combining sequence-based access and carrier sensing, this paper proposes a new protocol sequence-based scheme, called the PS-CS. We derive the theoretical average throughput, average access delay, worst-case delay, and average energy consumption of the PS-CS. It is shown that the PS-CS produces average throughput close to the optimal capacity of ${p}$ -persistent carrier sense multiple access (CSMA), and enjoys smaller access delay than the optimal ${p}$ -persistent CSMA. In addition, we study the energy-delay tradeoff, impact of carrier sensing fault and channel error, and how to modify the PS-CS to support real-time downlink for feedback control.

Tauberian Theorems for the ( $$\bar N$$ N ¯ , p m,n ) and (M, λ m,n ) Methods for Double Series over Ultrametric Fields

In this paper, K denotes a complete, non-trivially valued, non-archimedean (or ultrametric) field. Entries of double sequences, double series and 4-dimensional infinite matrices are in K.We prove Tauberian theorems for the Weighted Mean and (M,λ m,n ) methods for double series.

Identification, characterization and expression analysis of pigeonpea miRNAs in response to Fusarium wilt

Upon confrontation with unfavourable conditions, plants invoke a very complex set of biochemical and physiological reactions and alter gene expression patterns to combat the situations. MicroRNAs (miRNAs), a class of small non-coding RNA, contribute extensively in regulation of gene expression through translation inhibition or degradation of their target mRNAs during such conditions. Therefore, identification of miRNAs and their targets holds importance in understanding the regulatory networks triggered during stress. Structure and sequence similarity based in silico prediction of miRNAs in Cajanus cajan L. (Pigeonpea) draft genome sequence has been carried out earlier. These annotations also appear in related GenBank genome sequence entries. However, there are no reports available on context dependent miRNA expression and their targets in pigeonpea. Therefore, in the present study we addressed these questions computationally, using pigeonpea EST sequence information. We identified five novel pigeonpea miRNA precursors, their mature forms and targets. Interestingly, only one of these miRNAs (miR169i-3p) was identified earlier in draft genome sequence. We then validated expression of these miRNAs, experimentally. It was also observed that these miRNAs show differential expression patterns in response to Fusarium inoculation indicating their biotic stress responsive nature. Overall these results will help towards better understanding the regulatory network of defense during pigeonpea -pathogen interactions and role of miRNAs in the process.

A phylogenetic framework for the kingdom Fungi based on 18S rRNA gene sequences

The usage of molecular phylogenetic approaches is critical to advance the understanding of systematics and community processes in the kingdom Fungi. Among the possible phylogenetic markers (or combinations of them), the 18S rRNA gene appears currently as the most prominent candidate due to its large availability in public databases and informative content. The purpose of this work was the creation of a reference phylogenetic framework that can serve as ready-to-use package for its application on fungal classification and community analysis. The current database contains 9329 representative 18S rRNA gene sequences covering the whole fungal kingdom, a manually curated alignment, an annotated and revised phylogenetic tree with all the sequence entries, updated information on current taxonomy, and recommendations of use. Out of 201 total fungal taxa with more than two sequences in the dataset, 179 were monophyletic. From another perspective, 66% of the entries had a tree-derived classification identical to that obtained from the NCBI taxonomy, whereas 34% differed in one or the other rank. Most of the differences were associated to missing taxonomic assignments in NCBI taxonomy, or the unexpected position of sequences that positioned out of their theoretically corresponding clades. The strong correlation observed with current fungal taxonomy evidences that 18S rRNA gene sequence-based phylogenies are adequate to reflect genealogy of Fungi at the levels of order and above, and justify their further usage and exploration.

Differential representation of albumins and globulins during grain development in durum wheat and its possible functional consequences

Durum wheat (Triticum turgidum ssp. durum (Desf.) Husn.) is an economically important crop used for the production of semolina, which is the basis of pasta and other food products. Its grains provide proteins and starch for human consumption. Grain development is a key process in wheat physiology; it is highly affected by a number of enzymes that control the metabolic processes governing accumulation of starch and storage proteins and ultimately grain weight. Most of these enzymes are present in the albumin/globulin grain fraction, which represents about a quarter of total seed proteins. With the aim to describe the dynamic profile of the albumin/globulin fraction during durum wheat grain development, we performed a proteomic analysis of this subproteome using a two-dimensional differential gel electrophoresis (2D-DIGE)-based approach and compared six developmental stages. A total of 285 differentially (237 over- and 48 under-) represented spots was identified by nanoLC-ESI-LIT-MS/MS, which were associated with 217 non-redundant Triticum sequence entries. Quantitative protein dynamics demonstrated that carbon metabolism, energy, protein destination/storage, disease/defense and cell growth/division functional categories were highly affected during grain development, concomitantly with progressive grain size increase and starch/protein reserve accumulation. Bioinformatic interaction prediction revealed a complex network of differentially represented proteins mainly centered at enzymes involved in carbon and protein metabolism. A description of 18 proteins associated with wheat flour human allergies was also obtained; these components showed augmented levels at the last developmental stages. By providing a comprehensive understanding of the molecular basis of durum wheat grain development, yield and quality formation, this study provides the foundation and reveals potential biomarkers for further investigations of durum wheat breeding and semolina quality. Biological significanceA 2D-DIGE-based comparative analysis of the albumin/globulin fraction from durum wheat caryopses at six developmental stages was performed to describe the dynamic subproteomic changes associated with grain development. Quantitative variations of 217 differentially proteins demonstrated that highly affected are the functional categories of carbon metabolism, energy, protein destination/storage, disease/defense and cell growth/division, which displayed a general over-representation, consistently with concomitant occurrence of grain size increase and starch/protein reserve accumulation. Bioinformatics revealed a complex protein network centered mainly at enzymes involved in carbon and protein metabolism. Differentially represented proteins and corresponding functional categories highly resembled those previously identified as variable in developing bread wheat grain. This suggests that the main differences in kernel hardness between durum and bread wheat probably do not depend on proteomic changes in corresponding albumins/globulins, but on other specific factors affecting the interaction between the starch granules and the endosperm protein matrix in the kernel.

Bioinformatic Identification of Rare Codon Clusters (RCCs) in HBV Genome and Evaluation of RCCs in Proteins Structure of Hepatitis B Virus.

BackgroundHepatitis B virus (HBV) as an infectious disease that has nine genotypes (A - I) and a ‘putative’ genotype J.ObjectivesThe aim of this study was to identify the rare codon clusters (RCC) in the HBV genome and to evaluate these RCCs in the HBV proteins structure.MethodsFor detection of protein family accession numbers (Pfam) in HBV proteins, the UniProt database and Pfam search tool were used. Protein family accession numbers is a comprehensive and accurate collection of protein domains and families. It contains annotation of each family in the form of textual descriptions, links to other resources and literature references. Genome projects have used Pfam extensively for large-scale functional annotation of genomic data; Pfam database is a large collection of protein families, each represented by multiple sequence alignments and hidden Markov models (HMMs). The Pfam search tools are databases that identify Pfam of proteins. These Pfam IDs were analyzed in Sherlocc program and the location of RCCs in HBV genome and proteins were detected and reported as translated EMBL nucleotide sequence data library (TrEMBL) entries. The TrEMBL is a computer-annotated supplement of SWISS-PROT that contains all the translations of European molecular biology laboratory (EMBL) nucleotide sequence entries not yet integrated in SWISS-PROT. Furthermore, the structures of TrEMBL entries proteins were studied in the PDB database and 3D structures of the HBV proteins and locations of RCCs were visualized and studied using Swiss PDB Viewer software®.ResultsThe Pfam search tool found nine protein families in three frames. Results of Pfams studies in the Sherlocc program showed that this program has not identified RCCs in the external core antigen (PF08290) and truncated HBeAg gene (PF08290) of HBV. By contrast, the RCCs were identified in gene of hepatitis core antigen (PF00906 and the residues 224 - 234 and 251 - 255), large envelope protein S (PF00695 and the residues 53-56 and 70 - 84), X protein (PF00739 and the residues 10 - 24, 29 - 83, 95 - 99. 122 - 129, 139 - 143), DNA polymerase (viral) N-terminal domain (PF00242 and the residues 59 - 62, 214 - 217, 407 - 413) and protein P (Pf00336 and the residues 225 - 228). In HBV genome, seven RCCs were identified in the gene area of hepatitis core antigen, large envelope protein S and DNA polymerase, while protein structures of TrEMBL entries sequences found in Sherlocc program outputs were not complete.ConclusionsBased on the location of detected RCCs in the structure of HBV proteins, it was found that these RCCs may have a critical role in correct folding of HBV proteins and can be considered as drug targets. The results of this study provide new and deep perspectives about structure of HBV proteins for further researches and designing new drugs for treatment of HBV.

Palindrome analyser – A new web-based server for predicting and evaluating inverted repeats in nucleotide sequences

DNA cruciform structures play an important role in the regulation of natural processes including gene replication and expression, as well as nucleosome structure and recombination. They have also been implicated in the evolution and development of diseases such as cancer and neurodegenerative disorders. Cruciform structures are formed by inverted repeats, and their stability is enhanced by DNA supercoiling and protein binding. They have received broad attention because of their important roles in biology. Computational approaches to study inverted repeats have allowed detailed analysis of genomes. However, currently there are no easily accessible and user-friendly tools that can analyse inverted repeats, especially among long nucleotide sequences. We have developed a web-based server, Palindrome analyser, which is a user-friendly application for analysing inverted repeats in various DNA (or RNA) sequences including genome sequences and oligonucleotides. It allows users to search and retrieve desired gene/nucleotide sequence entries from the NCBI databases, and provides data on length, sequence, locations and energy required for cruciform formation. Palindrome analyser also features an interactive graphical data representation of the distribution of the inverted repeats, with options for sorting according to the length of inverted repeat, length of loop, and number of mismatches. Palindrome analyser can be accessed at http://bioinformatics.ibp.cz.

Strategies to improve usability and preserve accuracy in biological sequence databases.

Biology is increasingly dependent on large-scale analysis, such as proteomics, creating a requirement for efficient bioinformatics. Bioinformatic predictions of biological functions rely upon correctly annotated database sequences, and the presence of inaccurately annotated or otherwise poorly described sequences introduces noise and bias to biological analyses. Accurate annotations are, for example, pivotal for correct identification of polypeptide fragments. However, standards for how sequence databases are organized and presented are currently insufficient. Here, we propose five strategies to address fundamental issues in the annotation of sequence databases: (i) to clearly separate experimentally verified and unverified sequence entries; (ii) to enable a system for tracing the origins of annotations; (iii) to separate entries with high-quality, informative annotation from less useful ones; (iv) to integrate automated quality-control software whenever such tools exist; and (v) to facilitate postsubmission editing of annotations and metadata associated with sequences. We believe that implementation of these strategies, for example as requirements for publication of database papers, would enable biology to better take advantage of large-scale data.

Proteomic analysis reveals novel common genes modulated in both replicative and stress-induced senescence

Cellular senescence causes profound changes in gene expression profile. In this study, we used a combined 2D-DIGE and nanoLC-ESI-LIT-MS/MS approach to evaluate the proteomic changes occurring both in replicative and stress-induced senescence of human IMR90 cells. Twenty protein spots were identified as shifting their quantitative representation in the same direction (over- or down-represented) in both conditions of senescence, which were associated with 25 sequence entries. Dedicated experiments demonstrated that the decreased representation of a set of these proteins is associated with the down-regulation of the corresponding mRNAs, indicating that the regulation of these genes during the senescence process occurs at a transcriptional level. We also performed functional studies by silencing nine of these genes in young cells, which demonstrated that RNA interference-mediated knockdown of LEPRE1, LIMA1/EPLIN, MAGOHA and MAGOHB induces a premature senescent phenotype in IMR90 cells. Chromatin immunoprecipitation experiments indicated that the reduced expression of these four genes is associated with changes in the histone methylation pattern of their promoters, as proved by the occurrence of increased repressive H3K27me3 along with decreased active H3K4me3 marks, respectively. Biological significanceCellular senescence, a stable form of cell cycle arrest, is recognized as a phenomenon related to aging and age-related pathologies as well as interfering with tumor progression. Gene expression changes are closely associated with the onset of senescence but the molecular pathways regulating this process are still poorly understood. By using proteomics coupled to functional studies, we here show that both replicative and stress-induced senescence share quantitative modification of four novel proteins, in addition to others already reported in the literature. When ectopically down-regulated, corresponding four genes induce a premature senescence in young cells. The observed parallelism concerning the down-regulation of these genes both in vitro and in vivo senescent cells may foresee a possible biomarker role of the corresponding proteins in monitoring the progression of both aging and age-related diseases. In conclusion, these results for the first time highlight a possible role of LEPRE1, LIMA1/EPLIN, MAGOHA and MAGOHB in the biology of cellular senescence/aging, thus contributing to gain a deeper knowledge of the molecular mechanisms involved in the senescence program.

Steinhaus Type Theorems for \((c, 1)\) Summable Sequences

In this short paper, entries of infinite matrices and sequences are real or complex numbers. We prove a few Steinhaus type theorems for \((c, 1)\) summable sequences.

A New Definition of Convergence of a Double Sequence and a Double Series and Silverman-Toeplitz Theorem

Throughout this paper, entries of 4-dimensional infinite matrices, double sequences and double series are real or complex numbers. In the present paper, we introduce a new definition of convergence of a double sequence and a double series and record a few results on convergent double sequences. We also prove Silverman-Toeplitz theorem for double sequences and series.

INVARIANT CORE FOR DOUBLE SEQUENCES IN NON-ARCHIMEDEAN FIELDS

In this paper, K denotes a complete, non-trivially valued, non- archimedean field. The entries of sequences, series and infinite matrices are in K. In the present paper, we prove the Knopp's core theorem for double sequences in K and also the necessary and sufficient conditions for the core t be invariant under the four dimensional matrix transformation in such fields.

Expression And Purification of A Potential Antifolate Target, Dihydrofolate Reductase from B. malayi

Brugia malayi is one of the three causative parasites of lymphatic filariasis, or elephantiasis, a parasitic disease causing swelling of extremities and lymphatic damage. Current literature shows antifolate drugs inhibit B. malayi, suggesting that dihydrofolate reductase (DHFR) is a potential drug target for the elimination of the parasite. Conditions for the expression and purification of B. malayi DHFR have not previously been investigated. As such, this study aims to establish ideal conditions for the expression and purification of Bm‐DHFR, to determine kinetic values for the enzyme (kcat, Km, Vmax), and to study existing antifolate compounds as possible inhibitors. Initial work was completed using a Bm‐DHFR gene whose sequence was obtained from the UniProt database (accession number A8QGA9). When compared to the Bm‐DHFR sequence entry from Wormbase (BM34009), the UniProt sequence was found to be missing a loop known to play a role in catalysis (FG loop) consisting of residues #113‐125 in BM34009. The Uniprot Bm‐DHFR was difficult to express in soluble form and exhibited no catalytic activity. These findings correlate with previous studies showing that point mutations in the E. coli DHFR FG loop result in markedly decreased catalytic activity. A new Bm‐DHFR construct is currently being used with the sequence obtained from BM34009 entry. This Bm‐DHFR was designed incorporating an N‐terminal His6‐tag and was obtained in the pUC57 vector. Current work includes subcloning the gene into pET25b an E. coli expression plasmid. Expression and purification conditions will be optimized and Ki and IC­50 values will be determined for a set of DHFR inhibitors including trimethoprim and pyrimethamine to validate Bm‐DHFR as a priority drug target.

FASTAptamer: A Bioinformatic Toolkit for High-throughput Sequence Analysis of Combinatorial Selections.

High-throughput sequence (HTS) analysis of combinatorial selection populations accelerates lead discovery and optimization and offers dynamic insight into selection processes. An underlying principle is that selection enriches high-fitness sequences as a fraction of the population, whereas low-fitness sequences are depleted. HTS analysis readily provides the requisite numerical information by tracking the evolutionary trajectory of individual sequences in response to selection pressures. Unlike genomic data, for which a number of software solutions exist, user-friendly tools are not readily available for the combinatorial selections field, leading many users to create custom software. FASTAptamer was designed to address the sequence-level analysis needs of the field. The open source FASTAptamer toolkit counts, normalizes and ranks read counts in a FASTQ file, compares populations for sequence distribution, generates clusters of sequence families, calculates fold-enrichment of sequences throughout the course of a selection and searches for degenerate sequence motifs. While originally designed for aptamer selections, FASTAptamer can be applied to any selection strategy that can utilize next-generation DNA sequencing, such as ribozyme or deoxyribozyme selections, in vivo mutagenesis and various surface display technologies (peptide, antibody fragment, mRNA, etc.). FASTAptamer software, sample data and a user's guide are available for download at http://burkelab.missouri.edu/fastaptamer.html.

The Schur and Steinhaus Theorems for 4-Dimensional Infinite Matrices

This paper is a sequel to [2]. Throughout this paper, entries of double sequences, double series and 4-dimensional infinite matrices are real or complex numbers. We prove the Schur and Steinhaus theorems for 4-dimensional infinite matrices.

Dm-KDE: dynamical kernel density estimation by sequences of KDE estimators with fixed number of components over data streams

In many data stream mining applications, traditional density estimation methods such as kernel density estimation, reduced set density estimation can not be applied to the density estimation of data streams because of their high computational burden, processing time and intensive memory allocation requirement. In order to reduce the time and space complexity, a novel density estimation method Dm-KDE over data streams based on the proposed algorithm m-KDE which can be used to design a KDE estimator with the fixed number of kernel components for a dataset is proposed. In this method, Dm-KDE sequence entries are created by algorithm m-KDE instead of all kernels obtained from other density estimation methods. In order to further reduce the storage space, Dm-KDE sequence entries can be merged by calculating their KL divergences. Finally, the probability density functions over arbitrary time or entire time can be estimated through the obtained estimation model. In contrast to the state-of-the-art algorithm SOMKE, the distinctive advantage of the proposed algorithm Dm-KDE exists in that it can achieve the same accuracy with much less fixed number of kernel components such that it is suitable for the scenarios where higher on-line computation about the kernel density estimation over data streams is required.We compare Dm-KDE with SOMKE and M-kernel in terms of density estimation accuracy and running time for various stationary datasets. We also apply Dm-KDE to evolving data streams. Experimental results illustrate the effectiveness of the proposed method.