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PubMed2006

Genomics of the evolutionary process.

Comparative analysis of genome sequences has become the primary means by which functional elements are first identified, often preceding even the identification of their function. Although this approach capitalizes on the conservation of homologous functions, it has also been successful in identifying evolutionary novelties, including new genes and pathways. As I discuss here, the analysis of multiple alignments of sequences from species on a known phylogeny has provided rich detail about the heterogeneities in the process of genome changes. Inferences of positive selection acting on protein-encoding genes have provided clues about the role of adaptive evolution in the past. These methods also identify negatively selected genes, providing some clue to genes that are most likely to be mutable to a disease-causing state.

Adaptation, Biological↗
PubMed2004

Detecting overlapping coding sequences with pairwise alignments.

MOTIVATION: Overlapping gene coding sequences (CDSs) are particularly common in viruses but also occur in more complex genomes. Detecting such genes with conventional gene-finding algorithms can be difficult for several reasons. If an overlapping CDS is on the same read-strand as a known CDS, then there may not be a distinct promoter or mRNA. Furthermore, the constraints imposed by double-coding can result in atypical codon biases. However, these same constraints lead to particular mutation patterns that may be detectable in sequence alignments. RESULTS: In this paper, we investigate several statistics for detecting double-coding sequences with pairwise alignments--including a new maximum-likelihood method. We also develop a model for double-coding sequence evolution. Using simulated sequences generated with the model, we characterize the distribution of each statistic as a function of sequence composition, length, divergence time and double-coding frame. Using these results, we develop several algorithms for detecting overlapping CDSs. The algorithms were tested on known overlapping CDSs and other overlapping open reading frames (ORFs) in the hepatitis B virus (HBV), Escherichia coli and Salmonella typhimurium genomes. The algorithms should prove useful for detecting novel overlapping genes--especially short coding ORFs in viruses. AVAILABILITY: Programs may be obtained from the authors. SUPPLEMENTARY INFORMATION: http://biochem.otago.ac.nz/double.html.

Algorithms↗
PubMed2000

Heterogeneous Sp1 mRNAs in human HepG2 cells include a product of homotypic trans-splicing.

Sp1 is one of the well documented transcription factors, but the whole structure of human Sp1 has not been determined yet. In the present study, we isolated several cDNAs representing two forms of human Sp1 mRNA with different 5'-terminal structures in HepG2 cells. Isolation of a genomic clone established that one of the cDNAs represents the mRNA having consecutive alignment of exons, which allowed deducing the complete amino acid sequence for human Sp1. Another cDNA clone had a surprising structure that possessed an alignment of exons 3-2-3. Both reverse transcriptase-polymerase chain reaction and RNase protection assays confirmed accumulation of the two forms of Sp1 mRNA in HepG2 cells. Because Southern blot analysis suggested that exon 3 is of a single copy in the genome, the cDNA clone having the duplicated sequences for exon 3 appeared to reflect the trans-splicing between pre-mRNAs of human Sp1.

Amino Acid Sequence↗
PubMed2006

HOLLYWOOD: a comparative relational database of alternative splicing.

RNA splicing is an essential step in gene expression, and is often variable, giving rise to multiple alternatively spliced mRNA and protein isoforms from a single gene locus. The design of effective databases to support experimental and computational investigations of alternative splicing (AS) is a significant challenge. In an effort to integrate accurate exon and splice site annotation with current knowledge about splicing regulatory elements and predicted AS events, and to link information about the splicing of orthologous genes in different species, we have developed the Hollywood system. This database was built upon genomic annotation of splicing patterns of known genes derived from spliced alignment of complementary DNAs (cDNAs) and expressed sequence tags, and links features such as splice site sequence and strength, exonic splicing enhancers and silencers, conserved and non-conserved patterns of splicing, and cDNA library information for inferred alternative exons. Hollywood was implemented as a relational database and currently contains comprehensive information for human and mouse. It is accompanied by a web query tool that allows searches for sets of exons with specific splicing characteristics or splicing regulatory element composition, or gives a graphical or sequence-level summary of splicing patterns for a specific gene. A streamlined graphical representation of gene splicing patterns is provided, and these patterns can alternatively be layered onto existing information in the UCSC Genome Browser. The database is accessible at http://hollywood.mit.edu.

Alternative Splicing↗
PubMed2005

BarleyBase--an expression profiling database for plant genomics.

BarleyBase (BB) (www.barleybase.org) is an online database for plant microarrays with integrated tools for data visualization and statistical analysis. BB houses raw and normalized expression data from the two publicly available Affymetrix genome arrays, Barley1 and Arabidopsis ATH1 with plans to include the new Affymetrix 61K wheat, maize, soybean and rice arrays, as they become available. BB contains a broad set of query and display options at all data levels, ranging from experiments to individual hybridizations to probe sets down to individual probes. Users can perform cross-experiment queries on probe sets based on observed expression profiles and/or based on known biological information. Probe set queries are integrated with visualization and analysis tools such as the R statistical toolbox, data filters and a large variety of plot types. Controlled vocabularies for gene and plant ontologies, as well as interconnecting links to physical or genetic map and other genomic data in PlantGDB, Gramene and GrainGenes, allow users to perform EST alignments and gene function prediction using Barley1 exemplar sequences, thus, enhancing cross-species comparison.

Arabidopsis↗
PubMed2001

Evolution of the DUT gene: horizontal transfer between host and pathogen in all three domains of life.

The ubiquity of the dut gene in Eukarya, Eubacteria, and Archaea implies its existence in the last common ancestor of the three domains of life. The dut gene exists as single, tandemly duplicated, and tandemly triplicated copies. The dUTPase is encoded as an auxiliary gene in the genomes of several DNA viruses and two distinct lineages of retroviruses. A comprehensive analysis of dUTPase amino acid sequence relationships explores the evolutionary dynamics of dut genes in viruses and their hosts. The data set was comprised of representative sequences from available Eukaryotes, Archaea, Eubacteria cells and viruses. A multiple alignment of these protein sequences was generated using a hidden Markov model (HMM) approach developed to align divergent data. Phylogenetic analysis revealed that horizontal transfer from hosts to virus genomes has occurred in all three domains of life. The evidence for horizontal transfers is particularly interesting in Eukaryotes as these dut genes have introns, while DNA virus dut genes do not. This implies an intermediary Retroid Agent facilitated the horizontal transfer process, via reverse transcription, between host mRNA and DNA viruses. The horizontal transfer of the dut gene from Eukaryotic, Eubacterial, and Archaeal organisms to both DNA and RNA viruses is the first documented case of host to pathogen transfer that has occurred in all three domains of life.

Amino Acid Sequence↗
PubMed2001

General method of rapid Smith/Birnstiel mapping adds for gap closure in shotgun microbial genome sequencing projects: application to Pseudomonas putida KT2440.

A physical mapping strategy has been developed to verify and accelerate the assembly and gap closure phase of a microbial genome shotgun-sequencing project. The protocol was worked out during the ongoing Pseudomonas putida KT2440 genome project. A macro-restriction map was constructed by linking probe hybridisation of SwaI- or I-CeuI-restricted chromosomes to serve as a backbone for the quick quality control of sequence and contig assemblies. The library of PCR-generated SwaI linking probes was derived from the sequence assembly after 3- and 6-fold genome coverage. In order to support gap closure in regions with ambiguous assemblies such as the repetitive sequence of the seven ribosomal operons, high-resolution Smith/Birnstiel maps were generated by Southern hybridisation of pulsed-field gel electrophoresis-separated rare-cutter complete/frequent-cutter partial digestions with rare-cutter fragment end probes. Overall 1.5 Mb of the 6.1 Mb P.putida KT2440 genome has been subjected to high-resolution physical mapping in order to align assemblies generated from shotgun sequencing.

DNA, Bacterial↗
PubMed2006

Genome assembly comparison identifies structural variants in the human genome.

Numerous types of DNA variation exist, ranging from SNPs to larger structural alterations such as copy number variants (CNVs) and inversions. Alignment of DNA sequence from different sources has been used to identify SNPs and intermediate-sized variants (ISVs). However, only a small proportion of total heterogeneity is characterized, and little is known of the characteristics of most smaller-sized (<50 kb) variants. Here we show that genome assembly comparison is a robust approach for identification of all classes of genetic variation. Through comparison of two human assemblies (Celera's R27c compilation and the Build 35 reference sequence), we identified megabases of sequence (in the form of 13,534 putative non-SNP events) that were absent, inverted or polymorphic in one assembly. Database comparison and laboratory experimentation further demonstrated overlap or validation for 240 variable regions and confirmed >1.5 million SNPs. Some differences were simple insertions and deletions, but in regions containing CNVs, segmental duplication and repetitive DNA, they were more complex. Our results uncover substantial undescribed variation in humans, highlighting the need for comprehensive annotation strategies to fully interpret genome scanning and personalized sequencing projects.

Base Sequence↗
PubMed2004

MolliGen, a database dedicated to the comparative genomics of Mollicutes.

Bacteria belonging to the class Mollicutes were among the first ones to be selected for complete genome sequencing because of the minimal size of their genomes and their pathogenicity for humans and a broad range of animals and plants. At this time six genome sequences have been publicly released (Mycoplasma genitalium, Mycoplasma pneumoniae, Ureaplasma urealyticum-parvum, Mycoplasma pulmonis, Mycoplasma penetrans and Mycoplasma gallisepticum) and as the number of available mollicute genomes increases, comparative genomics analysis within this model group of organisms becomes more and more instructive. However, such an analysis is difficult to carry out without a suitable platform gathering not only the original annotations but also relevant information available in public databases or obtained by applying common bioinformatics methods. With the aim of solving these difficulties, we have developed a web-accessible database named MolliGen (http://cbi.labri.fr/outils/molligen/). After selecting a set of genomes the user can launch various types of search based on annotation, position on the chromosomes or sequence similarity. In addition, relationships of putative orthology have been precomputed to allow differential genome queries. The results are presented in table format with multiple links to public databases and to bioinformatic analyses such as multiple alignments or BLAST search. Specific tools were also developed for the graphical visualization of the results, including a multi- genome browser for displaying dynamic pictures with clickable objects and for viewing relationships of precomputed similarity. MolliGen is designed to integrate all the complete genomes of mollicutes as they become available.

Computational Biology↗
PubMed2005

Automated generation of heuristics for biological sequence comparison.

BACKGROUND: Exhaustive methods of sequence alignment are accurate but slow, whereas heuristic approaches run quickly, but their complexity makes them more difficult to implement. We introduce bounded sparse dynamic programming (BSDP) to allow rapid approximation to exhaustive alignment. This is used within a framework whereby the alignment algorithms are described in terms of their underlying model, to allow automated development of efficient heuristic implementations which may be applied to a general set of sequence comparison problems. RESULTS: The speed and accuracy of this approach compares favourably with existing methods. Examples of its use in the context of genome annotation are given. CONCLUSIONS: This system allows rapid implementation of heuristics approximating to many complex alignment models, and has been incorporated into the freely available sequence alignment program, exonerate.

Algorithms↗
PubMed2005

Characterization of canarypox-like viruses infecting endemic birds in the Galápagos Islands.

The presence of avian pox in endemic birds in the Galápagos Islands has led to concern that the health of these birds may be threatened by avipoxvirus introduction by domestic birds. We describe here a simple polymerase chain reaction-based method for identification and discrimination of avipoxvirus strains similar to the fowlpox or canarypox viruses. This method, in conjunction with DNA sequencing of two polymerase chain reaction-amplified loci totaling about 800 bp, was used to identify two avipoxvirus strains, Gal1 and Gal2, in pox lesions from yellow warblers (Dendroica petechia), finches (Geospiza spp.), and Galápagos mockingbirds (Nesomimus parvulus) from the inhabited islands of Santa Cruz and Isabela. Both strains were found in all three passerine taxa, and sequences from both strains were less than 5% different from each other and from canarypox virus. In contrast, chickens in Galápagos were infected with a virus that appears to be identical in sequence to the characterized fowlpox virus and about 30% different from the canarypox/Galápagos group viruses in the regions sequenced. These results indicate the presence of canarypox-like viruses in endemic passerine birds that are distinct from the fowlpox virus infecting chickens on Galápagos. Alignment of the sequence of a 5.9-kb region of the genome revealed that sequence identities among Gal1, Gal2, and canarypox viruses were clustered in discrete regions. This indicates that recombination between poxvirus strains in combination with mutation led to the canarypox-like viruses that are now prevalent in the Galápagos.

Amino Acid Sequence↗
PubMed1995

ALIGNMENT SERVICE: creation and processing of alignments of sequences of unlimited length.

A package for the creation and processing of multiple sequence alignment is described. There is no limit on the lengths of the processed nucleotide or amino acid sequences, and the number of sequences in the alignment is also unlimited. The main groups of functions are: a semiautomatic alignment editor; a wide set of functions for technical processing of alignments; nucleotide alignment mapping and translation; and similarity search functions. A user-friendly interface and a set of generally used file actions provide a special operational subsystem for everyday tasks.

Amino Acid Sequence↗
PubMed2006

Symmetric time warping, Boltzmann pair probabilities and functional genomics.

Given two time series, possibly of different lengths, time warping is a method to construct an optimal alignment obtained by stretching or contracting time intervals. Unlike pairwise alignment of amino acid sequences, classical time warping, originally introduced for speech recognition, is not symmetric in the sense that the time warping distance between two time series is not necessarily equal to the time warping distance of the reversal of the time series. Here we design a new symmetric version of time warping, and present a formal proof of symmetry for our algorithm as well as for one of the variants of Aach and Church [1]. We additionally design quadratic time dynamic programming algorithms to compute both the forward and backward Boltzmann partition functions for symmetric time warping, and hence compute the Boltzmann probability that any two time series points are aligned. In the future, with the availability of increasingly long and accurate time series gene expression data, our algorithm can provide a sense of biological significance for aligned time points - e.g. our algorithm could be used to provide evidence that expression values of two genes have higher Boltzmann probability (say) in the G1 and S phase than in G2 and M phases. Algorithms, source code and web interface, developed by the first author, are made publicly available via the Boltzmann Time Warping web server at bioinformatics.bc.edu/clotelab/.

Algorithms↗
PubMed2006

Phylogenetic analysis of beta-papillomaviruses as inferred from nucleotide and amino acid sequence data.

Human papillomaviruses (HPV) of the beta-group seem to be involved in the pathogenesis of non-melanoma skin cancer. Papillomaviruses are host specific and are considered closely co-evolving with their hosts. Evolutionary incongruence between early genes and late genes has been reported among oncogenic genital alpha-papillomaviruses and considerably challenge phylogenetic reconstructions. We investigated the relationships of 29 beta-HPV (25 types plus four putative new types, subtypes, or variants) as inferred from codon aligned and amino acid sequence data of the genes E1, E2, E6, E7, L1, and L2 using likelihood, distance, and parsimony approaches. An analysis of a L1 fragment included additional nucleotide and amino acid sequences from seven non-human beta-papillomaviruses. Early genes and late genes evolution did not conflict significantly in beta-papillomaviruses based on partition homogeneity tests (p > or = 0.001). As inferred from the complete genome analyses, beta-papillomaviruses were monophyletic and segregated into four highly supported monophyletic assemblages corresponding to the species 1, 2, 3, and fused 4/5. They basically split into the species 1 and the remainder of beta-papillomaviruses, whose species 3, 4, and 5 constituted the sistergroup of species 2. beta-Papillomaviruses have been isolated from humans, apes, and monkeys, and phylogenetic analyses of the L1 fragment showed non-human papillomaviruses highly polyphyletic nesting within the HPV species. Thus, host and virus phylogenies were not congruent in beta-papillomaviruses, and multiple invasions across species borders may contribute (additionally to host-linked evolution) to their diversification.

Amino Acid Sequence↗
PubMed2001

Attenuated lapinized chinese strain of classical swine fever virus: complete nucleotide sequence and character of 3'-noncoding region.

The complete nucleotide sequence including precise 5'- and 3'-terminal non-coding regions (NCRs) of the attenuated lapinized Chinese strain (HCLV) of Classical Swine Fever Virus (CSFV) was determined from overlapping cDNA clones constructed by separated RT-PCR and rapid amplification of cDNA ends (RACE) methods. The genomic RNA of the HCLV strain consists of 12.310 nucleotides (nts) including 374 nts and 242nts in the 5'- and 3'-NCRs, respectively. It contains one large open reading frame (ORF) encoding a polyprotein of 3,898 amino acids with a calculated molecular weight of 437.6 kDa. There is one notable insertion of 12 continuous nts, CTTTTTTCTTTT in the 3'-NCR of HCLV genomic cDNA when compared with its parental virulent Shimen strain. Sequence alignment of partial 3'-NCR reveals two groups of CSFV vaccine strains carrying similar T-rich insertions at different positions in this region. Computer-predicted secondary structures suggest that T-rich insertion greatly change the structures and thus decrease the promoter functions of 3'-NCRs during the replications of these two groups of CSFV vaccine strains.

3' Untranslated Regions↗
PubMed2005

Pattern profiling and mapping of the fat body transcriptome in Drosophila melanogaster.

In Drosophila, the fat body is a collective name for the masses and sheets of adipose tissue that are distributed throughout the fly body. Thus far, >386,000 Drosophila expressed sequence tags (ESTs) have been deposited to the GenBank database, including 10,443 derived from fat body in flies (data accessed on October 7, 2004). The objective of this study was to map the transcriptome of the fat body in flies and thus provide genomics and bioinformatics tools for developing a Drosophila model for addressing the genetic complexity of obesity in humans. The gene-EST Basic Local Alignment Search Tool (BLAST) matches revealed that these ESTs could represent 12,188 coding genes in the Drosophila genome. Among them, at least 2,261 are expressed in the fat body, including 41 identified as preferentially expressed genes with logarithm of odds >3.0. Self-organizing map analysis revealed a cluster of 290 genes favorably expressed in the fat body compared with genes expressed in five other tissues. Mapping of the fat body transcriptome identified a 1.7-Mb domain on 3L containing 35 genes that were expressed at a much higher level than in other tissues (transcript density factor = 1.0 approximately 2.3).

Animals↗
PubMed2024

The genomic route to tomato breeding: Past, present, and future.

Over the past 10,000 years, tomato species have undergone both unintentional and intentional selection to enhance their favorable traits for human consumption and manufacturing. These selection processes have significantly influenced the genomes of tomato species and have played a critical role in improving tomato varieties. In this review, we summarize recent advances in tomato genome sequencing, explore the impact of human-driven selection, and recapitulate key genes associated with important agronomic traits in tomato breeding. We provide several examples of genomics-guided tomato breeding to highlight the potential of genome resources in facilitating tomato improvement. Furthermore, we elaborate the progress and strategies of tomato breeding through genome design and present how such efforts can help future enhancements of tomato to align with the demands of sustainability and evolving human societies.

Solanum lycopersicum↗
PubMed2003

Identification and functional analysis of human transcriptional promoters.

Genomic and full-length cDNA sequences provide opportunities for understanding human gene structure and transcriptional regulatory elements. The simplest regulatory elements to identify are promoters, as their positions are dictated by the location of transcription start sites. We aligned full-length cDNA clones from the Mammalian Gene Collection to the human genome rough draft sequence to estimate the start sites of more than 10,000 human transcripts. We selected genomic sequence just upstream from the 5' end of these cDNA sequences and designated these as putative promoters. We assayed the functions of 152 of these DNA fragments, chosen at random from the entire set, in a luciferase-based transfection assay in four human cultured cell types. Ninety-one percent of these DNA fragments showed significant transcriptional activity in at least one of the cell lines, whereas 89% showed activity in at least two of the lines. We analyzed the distributions of strengths of these promoter fragments in the different cell types and identified likely alternative promoters in a large fraction of the genes. These data indicate that this approach is an effective method for predicting human promoters and provide the first set of functional data collected in parallel for a large set of human promoters.

Cell Line↗