NcDNAlign: plausible multiple alignments of non-protein-coding genomic sequences

Genome-wide multiple sequence alignments (MSAs) are a necessary prerequisite for an increasingly diverse collection of comparative genomic approaches. Here we present a versatile method that generates high-quality MSAs for non-protein-coding sequences. The NcDNAlign pipeline combines pairwise BLAST alignments to create initial MSAs, which are then locally improved and trimmed. The program is optimized for speed and hence is particulary well-suited to pilot studies. We demonstrate the practical use of NcDNAlign in three case studies: the search for ncRNAs in gammaproteobacteria and the analysis of conserved noncoding DNA in nematodes and teleost fish, in the latter case focusing on the fate of duplicated ultra-conserved regions. Compared to the currently widely used genome-wide alignment program TBA, our program results in a 20- to 30-fold reduction of CPU time necessary to generate gammaproteobacterial alignments. A showcase application of bacterial ncRNA prediction based on alignments of both algorithms results in similar sensitivity, false discovery rates, and up to 100 putatively novel ncRNA structures. Similar findings hold for our application of NcDNAlign to the identification of ultra-conserved regions in nematodes and teleosts. Both approaches yield conserved sequences of unknown function, result in novel evolutionary insights into conservation patterns among these genomes, and manifest the benefits of an efficient and reliable genome-wide alignment package. The software is available under the GNU Public License at http://www.bioinf.uni-leipzig.de/Software/NcDNAlign/.     

DNATagger, colors for codons

DNATagger is a web-based tool for coloring and editing DNA, RNA and protein sequences and alignments. It is dedicated to the visualization of protein coding sequences and also protein sequence alignments to facilitate the comprehension of evolutionary processes in sequence analysis. The distinctive feature of DNATagger is the use of codons as informative units for coloring DNA and RNA sequences. The codons are colored according to their corresponding amino acids. It is the first program that colors codons in DNA sequences without being affected by "out-of-frame" gaps of alignments. It can handle single gaps and gaps inside the triplets. The program also provides the possibility to edit the alignments and change color patterns and translation tables. DNATagger is a JavaScript application, following the W3C guidelines, designed to work on standards-compliant web browsers. It therefore requires no installation and is platform independent. The web-based DNATagger is available as free and open source software at http://www.inf.ufrgs.br/~dmbasso/dnatagger/.     

Hairpins in a Haystack: recognizing microRNA precursors in comparative genomics data

Recently, genome-wide surveys for non-coding RNAs have provided evidence for tens of thousands of previously undescribed evolutionary conserved RNAs with distinctive secondary structures. The annotation of these putative ncRNAs, however, remains a difficult problem. Here we describe an SVM-based approach that, in conjunction with a non-stringent filter for consensus secondary structures, is capable of efficiently recognizing microRNA precursors in multiple sequence alignments. The software was applied to recent genome-wide RNAz surveys of mammals, urochordates, and nematodes. AVAILABILITY: The program RNAmicro is available as source code and can be downloaded from http://www.bioinf.uni-leipzig/Software/RNAmicro.     

QPRIMER: a quick web-based application for designing conserved PCR primers from multigenome alignments

We have developed a quick web-based application for designing conserved genomic PCR and RT-PCR primers from multigenome alignments targeting specific exons or introns. We used Pygr (The Python Graph Database Framework for Bioinformatics) to query intervals from multigenome alignments, which gives us less than a millisecond access to any intervals of any genome within multigenome alignments. PRIMER3 was used to extract optimal primers from a gene of interest. QPRIMER creates an electronic genomic PCR image from a set of conserved primers as well as summary pages for primer alignments and products. QPRIMER supports human, mouse, rat, chicken, dog, zebrafish and fruit fly. Availability: http://www.bioinformatics.ucla.edu/QPRIMER/.     

The intronerator: exploring introns and alternative splicing in Caenorhabditis elegans

The Intronerator (http://www.cse.ucsc.edu/ approximately kent/intronerator/ ) is a set of web-based tools for exploring RNA splicing and gene structure in Caenorhabditis elegans. It includes a display of cDNA alignments with the genomic sequence, a catalog of alternatively spliced genes and a database of introns. The cDNA alignments include >100 000 ESTs and almost 1000 full-length cDNAs. ESTs from embryos and mixed stage animals as well as full-length cDNAs can be compared in the alignment display with each other and with predicted genes. The alt-splicing catalog includes 844 open reading frames for which there is evidence of alternative splicing of pre-mRNA. The intron database includes 28 478 introns, and can be searched for patterns near the splice junctions.     

Identification of protein sequence homology by consensus template alignment

A pattern-matching procedure is described, based on fitting templates to the sequence, which allows general structural constraints to be imposed on the patterns identified. The templates correspond to structurally conserved regions of the sequence and were initially derived from a small number of related sequences whose tertiary structures are known. The templates were then made more representative by aligning other sequences of unknown structure. Two alignments were built up containing 100 immunoglobulin variable domain sequences and 85 constant domain sequences, respectively. From each of these extended alignments, templates were generated to represent features conserved in all the sequences. These consisted mainly of patterns of hydrophobicity associated with beta-structure. For structurally conserved beta-strands with no conserved features, templates based on general secondary structure prediction principles were used to identify their possible locations. The specificity of the templates was demonstrated by their ability to identify the conserved features in known immunoglobulin and immunoglobulin-related sequences but not in other non-immunoglobulin sequences.     

EnteriX 2003: Visualization tools for genome alignments of Enterobacteriaceae

We describe EnteriX, a suite of three web-based visualization tools for graphically portraying alignment information from comparisons among several fixed and user-supplied sequences from related enterobacterial species, anchored on a reference genome (http://bio.cse.psu.edu/). The first visualization, Enteric, displays stacked pairwise alignments between a reference genome and each of the related bacteria, represented schematically as PIPs (Percent Identity Plots). Encoded in the views are large-scale genomic rearrangement events and functional landmarks. The second visualization, Menteric, computes and displays 1 Kb views of nucleotide-level multiple alignments of the sequences, together with annotations of genes, regulatory sites and conserved regions. The third, a Java-based tool named Maj, displays alignment information in two formats, corresponding roughly to the Enteric and Menteric views, and adds zoom-in capabilities. The uses of such tools are diverse, from examining the multiple sequence alignment to infer conserved sites with potential regulatory roles, to scrutinizing the commonalities and differences between the genomes for pathogenicity or phylogenetic studies. The EnteriX suite currently includes >15 enterobacterial genomes, generates views centered on four different anchor genomes and provides support for including user sequences in the alignments.     

Multiple non-collinear TF-map alignments of promoter regions

Background  

The analysis of the promoter sequence of genes with similar expression patterns is a basic tool to annotate common regulatory elements. Multiple sequence alignments are on the basis of most comparative approaches. The characterization of regulatory regions from co-expressed genes at the sequence level, however, does not yield satisfactory results in many occasions as promoter regions of genes sharing similar expression programs often do not show nucleotide sequence conservation.     

Homologies and anomalies in primary structural patterns of nucleotide binding proteins

In searches for homology among nucleotide binding proteins, recent reports have described primary structure alignments for stretches of 30 or so amino acid residues among a variety of proteins including the ras and src oncogene products. The significance of these sequence matches has been tested by searching in available data banks for certain conserved residue patterns resulting from the alignments. The tests suggest that alignments over these limited stretches are not necessarily justifiable and any implications for residues involved in nucleotide binding must be viewed with caution.     

Automated hierarchical classification of protein domain subfamilies based on functionally-divergent residue signatures

ABSTRACT: BACKGROUND: The NCBI Conserved Domain Database (CDD) consists of a collection of multiple sequence alignments of protein domains that are at various stages of being manually curated into evolutionary hierarchies based on conserved and divergent sequence and structural features. These domain models are annotated to provide insights into the relationships between sequence, structure and function via web-based BLAST searches. RESULTS: Here we automate the generation of conserved domain (CD) hierarchies using a combination of heuristic and Markov chain Monte Carlo sampling procedures and starting from a (typically very large) multiple sequence alignment. This procedure relies on statistical criteria to define each hierarchy based on the conserved and divergent sequence patterns associated with protein functional-specialization. At the same time this facilitates the sequence and structural annotation of residues that are functionally important. These statistical criteria also provide a means to objectively assess the quality of CD hierarchies, a non-trivial task considering that the protein subgroups are often very distantly related--a situation in which standard phylogenetic methods can be unreliable. Our aim here is to automatically generate (typically sub-optimal) hierarchies that, based on statistical criteria and visual comparisons, are comparable to manually curated hierarchies; this serves as the first step toward the ultimate goal of obtaining optimal hierarchical classifications. A plot of runtimes for the most time-intensive (non-parallelizable) part of the algorithm indicates a nearly linear time complexity so that, even for the extremely large Rossmann fold protein class, results are obtained in about a day. CONCLUSIONS: This approach automates the rapid creation of protein domain hierarchies and thus will eliminate one of the most time consuming aspects of conserved domain database curation. At the same time, it also facilitates protein domain annotation by identifying those pattern residues that most distinguish each protein domain subgroup from other related subgroups.     

Consensus folding of aligned sequences as a new measure for the detection of functional RNAs by comparative genomics

Facing the ever-growing list of newly discovered classes of functional RNAs, it can be expected that further types of functional RNAs are still hidden in recently completed genomes. The computational identification of such RNA genes is, therefore, of major importance. While most known functional RNAs have characteristic secondary structures, their free energies are generally not statistically significant enough to distinguish RNA genes from the genomic background. Additional information is required. Considering the wide availability of new genomic data of closely related species, comparative studies seem to be the most promising approach. Here, we show that prediction of consensus structures of aligned sequences can be a significant measure to detect functional RNAs. We report a new method to test multiple sequence alignments for the existence of an unusually structured and conserved fold. We show for alignments of six types of well-known functional RNA that an energy score consisting of free energy and a covariation term significantly improves sensitivity compared to single sequence predictions. We further test our method on a number of non-coding RNAs from Caenorhabditis elegans/Caenorhabditis briggsae and seven Saccharomyces species. Most RNAs can be detected with high significance. We provide a Perl implementation that can be used readily to score single alignments and discuss how the methods described here can be extended to allow for efficient genome-wide screens.     

cisprimertool: software to implement a comparative genomics strategy for the development of conserved intron scanning (CIS) markers

The availability of complete, annotated genomic sequence information in model organisms is a rich resource that can be extended to understudied orphan crops through comparative genomic approaches. We report here a software tool (cisprimertool) for the identification of conserved intron scanning regions using expressed sequence tag alignments to a completely sequenced model crop genome. The method used is based on earlier studies reporting the assessment of conserved intron scanning primers (called CISP) within relatively conserved exons located near exon-intron boundaries from onion, banana, sorghum and pearl millet alignments with rice. The tool is freely available to academic users at http://www.icrisat.org/gt-bt/CISPTool.htm.     

The EMOTIF database

The EMOTIF database is a collection of more than 170 000 highly specific and sensitive protein sequence motifs representing conserved biochemical properties and biological functions. These protein motifs are derived from 7697 sequence alignments in the BLOCKS+ database (released on June 23, 2000) and all 8244 protein sequence alignments in the PRINTS database (version 27.0) using the emotif-maker algorithm developed by Nevill-Manning et al. (Nevill-Manning,C.G., Wu,T.D. and Brutlag,D.L. (1998) Proc. Natl Acad. Sci. USA, 95, 5865-5871; Nevill-Manning,C.G., Sethi,K.S., Wu,T. D. and Brutlag,D.L. (1997) ISMB-97, 5, 202-209). Since the amino acids and the groups of amino acids in these sequence motifs represent critical positions conserved in evolution, search algorithms employing the EMOTIF patterns can identify and classify more widely divergent sequences than methods based on global sequence similarity. The emotif protein pattern database is available at http://motif.stanford.edu/emotif/.     

ddbRNA: detection of conserved secondary structures in multiple alignments

MOTIVATION: Structured non-coding RNAs (ncRNAs) have a very important functional role in the cell. No distinctive general features common to all ncRNA have yet been discovered. This makes it difficult to design computational tools able to detect novel ncRNAs in the genomic sequence. RESULTS: We devised an algorithm able to detect conserved secondary structures in both pairwise and multiple DNA sequence alignments with computational time proportional to the square of the sequence length. We implemented the algorithm for the case of pairwise and three-way alignments and tested it on ncRNAs obtained from public databases. On the test sets, the pairwise algorithm has a specificity greater than 97% with a sensitivity varying from 22.26% for Blast alignments to 56.35% for structural alignments. The three-way algorithm behaves similarly. Our algorithm is able to efficiently detect a conserved secondary structure in multiple alignments.     

EMBL-Align: a new public nucleotide and amino acid multiple sequence alignment database

The submission of multiple sequence alignment data to EMBL has grown 30-fold in the past 10 years, creating a problem of archiving them. The EBI has developed a new public database of multiple sequence alignments called EMBL-Align. It has a dedicated web-based submission tool, Webin-Align. Together they represent a comprehensive data management solution for alignment data. Webin-Align accepts all the common alignment formats and can display data in CLUSTALW format as well as a new standard EMBL-Align flat file format. The alignments are stored in the EMBL-Align database and can be queried from the EBI SRS (Sequence Retrieval System) server. AVAILABILITY: Webin-Align: http://www.ebi.ac.uk/embl/Submission/align_top.html, EMBL-Align: ftp://ftp.ebi.ac.uk/pub/databases/embl/align, http://srs.ebi.ac.uk/