NCBI Virus is an integrative, value-added resource designed to support retrieval, display and analysis of a curated collection of virus sequences and large sequence datasets. Its goal is to increase the usability of viral sequence data archived in GenBank and other NCBI repositories. This resource includes resources previously included in HIV-1, Human Protein Interaction Database, Influenza Virus Resource, and Virus Variation.
Complete genome sequence of a novel extrachromosomal virus-like element identified in planarian
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Background Freshwater planarians are widely used as models for investigation of pattern formation and studies on genetic variation in populations. Despite extensive information on the biology and genetics of planaria, the occurrence and distribution of viruses in these animals remains an unexplored area of research. Results Using a combination of Suppression Subtractive Hybridization (SSH) and Mirror Orientation Selection (MOS), we compared the genomes of two strains of freshwater planarian, Girardia tigrina. The novel extrachromosomal DNA-containing virus-like element denoted PEVE (Planarian Extrachromosomal Virus-like Element) was identified in one planarian strain. The PEVE genome (about 7.5 kb) consists of two unique regions (Ul and Us) flanked by inverted repeats. Sequence analyses reveal that PEVE comprises two helicase-like sequences in the genome, of which the first is a homolog of a circoviral replication initiator protein (Rep), and the second is similar to the papillomavirus E1 helicase domain. PEVE genome exists in at least two variant forms with different arrangements of single-stranded and double-stranded DNA stretches that correspond to the Us and Ul regions. Using PCR analysis and whole-mount in situ hybridization, we characterized PEVE distribution and expression in the planarian body. Conclusions PEVE is the first viral element identified in free-living flatworms. This element differs from all known viruses and viral elements, and comprises two potential helicases that are homologous to proteins from distant viral phyla. PEVE is unevenly distributed in the worm body, and is detected in specific parenchyma cells.
VirOligo: a database of virus-specific oligonucleotides
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VirOligo is a database of virus-specific oligonucleotides. The VirOligo database consists of two tables, Common data and Oligo data. The Oligo data table contains PCR primers and hybridization probes used for detection of viral nucleic acids and the Common data table contains the experimental conditions used in their detection. Each oligonucleotide entry contains links to PubMed, GenBank, NCBI Taxonomy databases and BLAST. As of July 2001, the VirOligo database contains a complete listing of oligonucleotides specific to viral agents associated with bovine respiratory disease that were published in English in peer-reviewed journals. The viruses are bovine herpes virus types 1, 3, 4 and 5, bovine viral diarrhea virus, bovine parainfluenza 3 virus, bovine respiratory syncytial virus, bovine adenovirus, bovine rhinovirus, bovine coronavirus, bovine reovirus, bovine enterovirus and alcelaphine herpesvirus-1. The VirOligo database is being expanded to other viruses and can be accessed through the Internet at http://viroligo.okstate.edu/.
An algorithm for mapping positively selected members of quasispecies-type viruses
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Background Many RNA viruses do not have a single, representative genome but instead form a set of related variants that has been called a quasispecies. The sequence variability of such viruses presents a significant bioinformatics challenge. In order for the sequence information to be understood, the complete mutational spectrum needs to be distilled to a biologically relevant and analyzable representation. Results Here, we develop a "selection mapping" algorithm--QUASI--that identifies the positively selected variants of viral proteins. The key to the selection mapping algorithm is the identification of particular replacement mutations that are overabundant relative to silent mutations at each codon (e.g., threonine at hemagglutinin position 262). Selection mapping identifies such replacement mutations as positively selected. Conversely, selection mapping recognizes negatively selected variants as mutational "noise" (e.g., serine at hemagglutinin position 262). Conclusion Selection mapping is a fundamental improvement over earlier methods (e.g., dN/dS) that identify positive selection at codons but do not identify which amino acids at these codons confer selective advantage. Using QUASI's selection maps, we characterize the selected mutational landscapes of influenza A H3 hemagglutinin, HIV-1 reverse transcriptase, and HIV-1 gp120.