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PubMed2004

dictyBase: a new Dictyostelium discoideum genome database.

Dictyostelium discoideum is a powerful and genetically tractable model system used for the study of numerous cellular molecular mechanisms including chemotaxis, phagocytosis and signal transduction. The past 2 years have seen a significant expansion in the scope and accessibility of online resources for Dictyostelium. Recent advances have focused on the development of a new comprehensive online resource called dictyBase (http://dictybase.org). This database not only provides access to genomic data including functional annotation of genes, gene products and chromosomal mapping, but also to extensive biological information such as mutant phenotypes and corresponding reference material. In conjunction with additional sites (http://genome. imb-jena.de/dictyostelium/, http://dictyensembl. bioch.bcm.tmc.edu and http://www.sanger.ac.uk/Projects/D_discoideum/) from the genome sequencing and assembly centers, these improvements have expanded the scope of the Dictyostelium databases making them accessible and useful to any researcher interested in comparative and functional genomics in metazoan organisms.

Animals↗
PubMedDate not supplied

The Trypanosoma cruzi genome project: nuclear karyotype and gene mapping of clone CL Brener.

By using improved pulsed field gel electrophoresis conditions, the molecular karyotype of the reference clone CL Brener selected for Trypanosoma cruzi genome project was established. A total of 20 uniform chromosomal bands ranging in size from 0.45 to 3.5 Megabase pairs (Mbp) were resolved in a single run. The weighted sum of the chromosomal bands was approximately 87 Mbp. Chromoblots were hybridized with 39 different homologous probes, 13 of which identified single chromosomes. Several markers showed linkage and four different linkage groups were identified, each comprising two markers. Densitometric analysis suggests that most of the chromosomal bands contain two or more chromosomes representing either homologous chromosomes and/or heterologous chromosomes with similar sizes.

Animals↗
PubMed1975

DNA-RNA hybridization.

Interest in nucleic acid hybridization stems mainly from its great power as a tool in biological research. It is used in several quite distinct ways. Because of the high degree of specificity that they show, hybridization techniques can be used to measure the amount of one specific sequence within a very heterogeneous mixture of sequences. Measurements of 1/10(6)-10(7) have been recorded. In extension of this, various properties of a specific sequence can often be studied. Secondly, because the kinetics of nucleic acid hybridization are quite well understood, it can be used to characterize both a pure sequence and a very complex mixture of sequences, like the genome of a vertebrate. Thirdly, again because of its specificity, it can be used to measure homologies between different populations of nucleic acids. Lastly, in conjunction with other techniques, it can be used as a basis for the fractionation of nucleic acid populations and the purification of specific sequences. Specific examples of these applications are given, with special reference to the organization of the genome in higher eukaryotes.

Animals↗
PubMed2005

A homolog of the human chemokine receptor CXCR1 is expressed in the mouse.

Two distinct genes are present in the human genome encoding receptors for human interleukin-8 (hCXCL8), referred to as hCXCR1 and hCXCR2. While it seems clear that orthologous genes are present in the genomes of several mammals, the existence of a gene encoding an ortholog of hCXCR1 in the mouse has thus far been controversial. We have isolated a cDNA that is highly similar to the cDNAs of hCXCR1 and hCXCR2, but is clearly distinct from the cDNA encoding mouse CXCR2 (mCXCR2). The encoded protein, designated mouse CXCR1-like (mCXCR1-like), shares 64, 57, 57, and 89% identical amino acids with hCXCR1, hCXCR2, mCXCR2, and rCXCR1-like, respectively. The gene encoding mCXCR1-like was mapped to mouse chromosome 1 and its genomic organization was determined to be very similar to the organization of the gene encoding hCXCR1. Like hCXCR1, mCXCR1-like was found to be expressed at the mRNA level in neutrophils. In addition, mRNA encoding mCXCR1-like was detected in liver, kidney, and spleen. In spleen, mCXCR1-like transcripts were predominantly found in CD4+ T cells. In liver, mCXCR1-like transcripts were identified in residual CD3+ T cells and macrophages, suggesting that mCXCR1-like may regulate inflammatory and immunological processes in the liver. When expressed as a recombinant protein, mCXCR1-like was not activated by a large panel of known CXC chemokines of human and murine origin. These findings suggest that a homolog or ortholog of hCXCR1 is expressed in the mouse to be activated by a hitherto unknown CXC chemokine of the mouse.

Amino Acid Sequence↗
PubMed2026

A novel transformer model of protein domains for viral taxonomy classification.

MOTIVATION: Viruses with carefully curated taxonomic assignments (such as those in the ICTV taxonomy) still represent only a small fraction of viruses identified through sequencing data from virome or microbiome projects. It is therefore critical to develop methods that can assign viruses at multiple taxonomic ranks, so that a virus deemed novel at a given rank may still be placed into a higher-level taxon. Sequence-similarity-based approaches can classify viruses that share substantial genomic similarity with known viruses (e.g. those belonging to the same species or genus); however, their performance drops significantly when applied to more divergent viruses. Recent deep learning models, such as ViTax, which utilize DNA language models, aim to address these limitations, but their performance also degrades when applied to novel viruses lacking genus-level similarity to known references. Proteins are more conserved than genomic sequences, and the multiple proteins encoded by a virus can be leveraged to reveal evolutionary relationships among viruses. RESULTS: We propose a new tool, D2T (Domain-to-Taxonomy), that leverages recent advances in protein language models to improve viral taxonomic assignment. D2T represents a virus as a sequence of protein domain tokens and learns a transformer-based model for taxonomic classification. Experiments on multiple closed-set and open-set datasets show that D2T excels at assigning higher-level taxonomic labels (family and above). Furthermore, by combining D2T with Kraken2, which performs well at the genus level, the hybrid method (K+D2T) achieves accurate viral taxonomic classification across multiple taxonomic ranks. AVAILABILITY AND IMPLEMENTATION: D2T is available as a GitHub repository at https://github.com/mgtools/D2T.

Viruses↗
PubMed1984

Genome variants of human adenovirus 40 (subgroup F).

Twenty-six strains of faecal adenovirus from three continents (two from Europe, 16 from South Africa, and eight from Canada) were typed as Ad40 by restriction enzyme analysis of the DNA using Sma I. The DNA of the strains was further compared by digestion with six other enzymes, namely Bam HI, Eco RI, Bgl I, Xho I, Sst I, and Hind III. At least two different restriction profiles were found to exist for each enzyme. Nineteen of the 26 strains studied had the same combination of profiles for all the enzymes, within the limits of resolution of the technique. This genome type was detected from all three continents and included the Finnish reference strain Hovi-X. The other seven strains were genome variants, representing five other genome types. Three genome types were detected only in South African specimens, whereas one genome type was detected in single specimens from both South Africa and Canada. Strain Dugan from Holland, indistinguishable from other Ad40 strains in neutralization tests using polyclonal antibody preparations [de Jong et al, 1983], deviated from the common Hovi-X-like genome on digestion of the DNA with any of the enzymes except Sma I.

Adenoviridae Infections↗
PubMed2005

Species-level identification of isolates of the Acinetobacter calcoaceticus-Acinetobacter baumannii complex by sequence analysis of the 16S-23S rRNA gene spacer region.

The species Acinetobacter calcoaceticus, A. baumannii, genomic species 3, and genomic species 13TU included in the Acinetobacter calcoaceticus-Acinetobacter baumannii complex are genetically highly related and difficult to distinguish phenotypically. Except for A. calcoaceticus, they are all important nosocomial species. In the present study, the usefulness of the 16S-23S rRNA gene intergenic spacer (ITS) sequence for the differentiation of (genomic) species in the A. calcoaceticus-A. baumannii complex was evaluated. The ITSs of 11 reference strains of the complex and 17 strains of other (genomic) species of Acinetobacter were sequenced. The ITS lengths (607 to 638 bp) and sequences were highly conserved for strains within the A. calcoaceticus-A. baumannii complex. Intraspecies ITS sequence similarities ranged from 0.99 to 1.0, whereas interspecies similarities varied from 0.86 to 0.92. By using these criteria, 79 clinical isolates identified as A. calcoaceticus (18 isolates) or A. baumannii (61 isolates) with the API 20 NE system (bioMerieux Vitek, Marcy l'Etoile, France) were identified as A. baumannii (46 isolates), genomic species 3 (19 isolates), and genomic species 13TU (11 isolates) by ITS sequencing. An identification rate of 96.2% (76 of 79 isolates) was obtained by using ITS sequence analysis for identification of isolates in the A. calcoaceticus-A. baumannii complex, and the accuracy of the method was confirmed for a subset of strains by amplified rRNA gene restriction analysis and genomic DNA analysis by AFLP analysis by using libraries of profiles of reference strains. In conclusion, ITS sequence-based identification is reliable and provides a promising tool for elucidation of the clinical significance of the different species of the A. calcoaceticus-A. baumannii complex.

Acinetobacter baumannii↗
PubMed1993

The human aquaporin-CHIP gene. Structure, organization, and chromosomal localization.

Aquaporin-CHIP is the first known molecular water channel. Originally identified in red cells and renal tubules, transcripts and proteins related to AQP-CHIP are also expressed in diverse epithelia with distinct developmental patterns. Northern analyses of RNA from several tissues revealed transcripts of 3.1 kilobases and other sizes. The nucleotide sequences of human kidney AQP-CHIP cDNAs are identical to the human bone marrow AQP-CHIP cDNA. The 17-kilobase human AQP-CHIP structural gene was isolated, and restriction maps were constructed and partially sequenced. The TATA consensus sequence is located 87 bp 5' to the translation initiation site, and sequences surrounding the polyadenylation consensus were determined. Four exons were identified corresponding to amino acids 1-128, 129-183, 184-210, and 211-269, separated by introns of 9.6, 0.43, and 0.80 kilobases. Genomic Southern analyses indicated the existence of a single AQP-CHIP gene which was located at human chromosome 7p14 by in situ hybridization. Sequence comparisons of AQP-CHIP and cDNAs of similar proteins from diverse species suggested a common evolutionary origin. At least three of these proteins are now known to function as membrane water pores and are referred to as the "Aquaporins." These genomic AQP-CHIP DNA sequences should permit molecular characterization of the complex patterns of AQP-CHIP expression.

Animals↗
PubMed2003

Frequent reassortment among influenza C viruses.

In a 9-year survey from December 1990 to December 1999 in Sendai City, Japan, we succeeded in isolating a total of 45 strains of influenza C virus. These 45 strains were isolated in clusters within 4 months in a year, especially from winter to early summer. Previous studies of the hemagglutinin-esterase genes of various influenza C virus isolates revealed the existence of five distinct virus lineages (Aichi/1/81-, Yamagata/26/81-, Mississippi/80-, Sao Paulo/82-, and Kanagawa/1/76-related lineage) in Japan between 1970 and the early 1990s (Y. Matsuzaki, K. Mizuta, H. Kimura, K. Sugawara, E. Tsuchiya, H. Suzuki, S. Hongo, and K. Nakamura, J. Gen. Virol. 81:1447-1452, 2000). Antigenic and genetic analyses of the 45 strains showed that they could be divided into these five virus lineages and a few antigenic groups were cocirculating in Sendai City. In 1990 and 1991 the dominant antigenic group was the Aichi/1/81 virus group, and in 1992 it was Yamagata/26/81 virus group. The Mississippi/80 virus group was isolated from 1993 to 1996, and the Yamagata/26/81 virus group reemerged in 1996 and continued to circulate until 1999. This finding led us to a speculation that the replacement of the dominant antigenic groups had occurred by immune selection within the human population in the restricted area. Phylogenetic analysis of seven RNA segments showed that 44 viruses among the 45 strains isolated in our surveillance work were reassortant viruses that have various genome compositions distinguishable from those of the reference strains of the each lineage. This observation suggests that the reassortment between two different influenza C virus strains occurs frequently in nature and the genome composition of influenza C viruses may influence their ability to spread in humans.

Antigens, Viral↗
PubMed2002

Expressed sequence tags for the chicken genome from a normalized 10-day-old white leghorn whole-embryo cDNA library. 3. DNA sequence analysis of genetic variation in commercial chicken populations.

Single nucleotide polymorphisms (SNPs) have emerged as a major class of DNA markers with the advantage of permitting the development of high-density genetic maps adequate for quantitative trait loci (QTL) identification by linkage-disequilibrium analysis. Here we describe results of a relatively high-depth survey of chicken broiler and layer populations for SNPs in targeted genomic regions of chicken expressed sequence tag (EST) sites. The sequences scanned, representing the composite sequence of 12 amplified fragments for a total of 6489 bp, were randomly distributed, occurring on six different chromosomes or linkage groups in the chicken genome. Although one of the genomic DNA sequences did not match the reference cDNA sequence, another contained an intron that separated two putative exons. The number of SNPs observed within each of the 12 EST-targeted genomic regions ranged from 0 to 10 for a total of 44 and a frequency of 0.7%. About 70% of the polymorphisms were shared between layer and broiler populations. The average heterozygosity within the populations ranged from 0.15 to 0.48, with the layer populations showing the higher heterozygosity. SNPs and oligonucleotides described will provide a resource for genetic analysis in commercial chicken populations. The data appear to indicate that the relative frequency of SNPs in the targeted regions scanned is higher than the frequency reported for any of the other regions scanned to date in other eukaryotic genomes. Additionally, the results suggest that the use of DNA pools may offer an efficient approach to SNP detection in chickens, as has been shown in other vertebrates.

Animals↗
PubMed2003

Transcription termination at the mouse mitochondrial H-strand promoter distal site requires an A/T rich sequence motif and sequence specific DNA binding proteins.

Termination of mitochondrial (mt) H-strand transcription in mammalian cells occurs at two distinct sites on the genome. The first site of termination, referred to as mt-TERM occurs beyond the 16 S rRNA gene. However, the second and final site of termination beyond the tRNAThr gene remains unclear. In this study we have characterized the site of termination of the polycistronic distal gene transcript beyond the D-loop region, immediately upstream of the tRNAPhe gene. This region, termed D-TERM, maps to nucleotides 16274-16295 of the mouse genome and includes a conserved A/T rich sequence motif AATAAA as a part of the terminator. Gel-shift analysis showed that the 22 bp D-TERM DNA forms two major complexes with mouse liver mt extract in a sequence-specific manner. Protein purification by DNA-affinity chromatography yielded two major proteins of 45 kDa and 70 kDa. Finally, the D-TERM DNA can mediate transcription termination in a unidirectional manner in a HeLa mt transcription system, only in the presence of purified mouse liver mt D-TERM DNA binding proteins. We have therefore characterized a novel mt transcription termination system, similar in some properties to that of sea urchin, as well as the nuclear RNA Pol I and Pol II transcription termination systems.

AT Rich Sequence↗
PubMed2005

Predicted highly expressed genes in the genomes of Streptomyces coelicolor and Streptomyces avermitilis and the implications for their metabolism.

Highly expressed genes in bacteria often have a stronger codon bias than genes expressed at lower levels, due to translational selection. In this study, a comparative analysis of predicted highly expressed (PHX) genes in the Streptomyces coelicolor and Streptomyces avermitilis genomes was performed using the codon adaptation index (CAI) as a numerical estimator of gene expression level. Although it has been suggested that there is little heterogeneity in codon usage in G+C-rich bacteria, considerable heterogeneity was found among genes in these two G+C-rich Streptomyces genomes. Using ribosomal protein genes as references, approximately 10% of the genes were predicted to be PHX genes using a CAI cutoff value of greater than 0.78 and 0.75 in S. coelicolor and S. avermitilis, respectively. The PHX genes showed good agreement with the experimental data on expression levels obtained from proteomic analysis by previous workers. Among 724 and 730 PHX genes identified from S. coelicolor and S. avermitilis, 368 are orthologue genes present in both genomes, which were mostly 'housekeeping' genes involved in cell growth. In addition, 61 orthologous gene pairs with unknown functions were identified as PHX. Only one polyketide synthase gene from each Streptomyces genome was predicted as PHX. Nevertheless, several key genes responsible for producing precursors for secondary metabolites, such as crotonyl-CoA reductase and propionyl-CoA carboxylase, and genes necessary for initiation of secondary metabolism, such as adenosylmethionine synthetase, were among the PHX genes in the two Streptomyces species. The PHX genes exclusive to each genome, and what they imply regarding cellular metabolism, are also discussed.

Bacterial Proteins↗
PubMed1997

Sequence mapping by electronic PCR

The highly specific and sensitive PCR provides the basis for sequence-tagged sites (STSs), unique landmarks that have been used widely in the construction of genetic and physical maps of the human genome. Electronic PCR (e-PCR) refers to the process of recovering these unique sites in DNA sequences by searching for subsequences that closely match the PCR primers and have the correct order, orientation, and spacing that they could plausibly prime the amplification of a PCR product of the correct molecular weight. A software tool was developed to provide an efficient implementation of this search strategy and allow the sort of en masse searching that is required for modern genome analysis. Some sample searches were performed to demonstrate a number of factors that can affect the likelihood of obtaining a match. Analysis of one large sequence database record revealed the presence of several microsatellite and gene-based markers and allowed the exact base-pair distances among them to be calculated. This example provides a demonstration of how e-PCR can be used to integrate the growing body of genomic sequence data with existing maps, reveal relationships among markers that existed previously on different maps, and correlate genetic distances with physical distances.

Base Sequence↗
PubMed1983

Alignment of the genome of monkey B-lymphotropic papovavirus to the genomes of simian virus 40 and BK virus.

We located the origin of DNA replication of African green monkey B-lymphotropic papovavirus DNA by analyzing pulse-labeled form I DNA. With the replication origin used as a reference point, the B-lymphotropic papovavirus genome was aligned with the genomes of simian virus 40 and BK virus from DNA homology between specific fragments hybridized under low-stringency conditions. From the results of these experiments, it was possible to deduce the correlation between the physical and functional maps of the B-lymphotropic papovavirus genome.

BK Virus↗
PubMed1995

Characterization of human lymphoid cell lines GM9947 and GM9948 as intra- and interlaboratory reference standards for DNA typing.

The incorporation of reference DNA is crucial to the validation of any DNA typing protocol. Currently, reference DNA standards are restricted to molecular size DNA ladders and/or tumor cell line DNA. Either of these, however, presents some limitations. We have rigorously characterized two Epstein-Barr virus (EBV)-immortalized human lymphoid cell lines--GM9947 (female) and GM9948 (male)--to determine their suitability as alternative in-line standards for three widely employed allele profiling strategies. Twenty-one highly polymorphic VNTR-based allelic systems (7 RFLPs, 2 AmpFLPs, and 12 STRs) distributed over 12 chromosomes were scrutinized along with 3 gender-based discriminatory systems. The genetic stability of each locus was confirmed over a period of 225 in vitro population doublings. Allele size estimates and degree of informativeness for each of the 21 VNTR systems were compiled. The reproducibility of allele scoring by traditional RFLP analyses, using both cell lines as reference standards, was also verified by an interlaboratory validation study involving 13 analysts from two geographically distinct forensic laboratories. Taken together, our data indicate that GM9947 and GM9948 genomic DNAs could be adopted as reliable reference standards for DNA typing.

Base Sequence↗
PubMed2006

MIPS: analysis and annotation of proteins from whole genomes in 2005.

The Munich Information Center for Protein Sequences (MIPS at the GSF), Neuherberg, Germany, provides resources related to genome information. Manually curated databases for several reference organisms are maintained. Several of these databases are described elsewhere in this and other recent NAR database issues. In a complementary effort, a comprehensive set of >400 genomes automatically annotated with the PEDANT system are maintained. The main goal of our current work on creating and maintaining genome databases is to extend gene centered information to information on interactions within a generic comprehensive framework. We have concentrated our efforts along three lines (i) the development of suitable comprehensive data structures and database technology, communication and query tools to include a wide range of different types of information enabling the representation of complex information such as functional modules or networks Genome Research Environment System, (ii) the development of databases covering computable information such as the basic evolutionary relations among all genes, namely SIMAP, the sequence similarity matrix and the CABiNet network analysis framework and (iii) the compilation and manual annotation of information related to interactions such as protein-protein interactions or other types of relations (e.g. MPCDB, MPPI, CYGD). All databases described and the detailed descriptions of our projects can be accessed through the MIPS WWW server (http://mips.gsf.de).

Animals↗
PubMed1989

Characterization of a simian hepatitis A virus (HAV): antigenic and genetic comparison with human HAV.

PA21, a strain of hepatitis A virus (HAV) recovered from a naturally infected captive owl monkey, is indistinguishable from human HAV in polyclonal radioimmunoassays and cross-neutralization studies. However, cDNA-RNA hybridization has suggested a significant difference at the genomic level between PA21 and a reference human virus, HM175. Further characterization of this unique HAV was undertaken in an effort to determine the extent of genetic divergence from human HAV and its relation to the conserved antigenic structure of the virus. The close similarity between PA21 and HM175 antigens was confirmed with an extended panel of 18 neutralizing murine monoclonal antibodies: a reproducible difference in binding to the two viruses was detected with only one antibody (B5-B3). The nucleotide sequence of the P1 region of the PA21 genome had only 83.2% identity with HM175 virus, a difference approximately twice as great as that found between any two human strains. Most nucleotide changes were in third base positions, and the amino acid sequences of the capsid proteins were largely conserved. Amino acid replacements were clustered in the carboxy terminus of VP1 and the amino-terminal regions of VP2 and VP1. These data indicate that PA21 virus represents a unique genotype of HAV and suggest the existence of an ecologically isolated niche for HAV among feral owl monkeys.

Amino Acid Sequence↗
PubMed2006

Towards the identification of essential genes using targeted genome sequencing and comparative analysis.

BACKGROUND: The identification of genes essential for survival is of theoretical importance in the understanding of the minimal requirements for cellular life, and of practical importance in the identification of potential drug targets in novel pathogens. With the great time and expense required for experimental studies aimed at constructing a catalog of essential genes in a given organism, a computational approach which could identify essential genes with high accuracy would be of great value. RESULTS: We gathered numerous features which could be generated automatically from genome sequence data and assessed their relationship to essentiality, and subsequently utilized machine learning to construct an integrated classifier of essential genes in both S. cerevisiae and E. coli. When looking at single features, phyletic retention, a measure of the number of organisms an ortholog is present in, was the most predictive of essentiality. Furthermore, during construction of our phyletic retention feature we for the first time explored the evolutionary relationship among the set of organisms in which the presence of a gene is most predictive of essentiality. We found that in both E. coli and S. cerevisiae the optimal sets always contain host-associated organisms with small genomes which are closely related to the reference. Using five optimally selected organisms, we were able to improve predictive accuracy as compared to using all available sequenced organisms. We hypothesize the predictive power of these genomes is a consequence of the process of reductive evolution, by which many parasites and symbionts evolved their gene content. In addition, essentiality is measured in rich media, a condition which resembles the environments of these organisms in their hosts where many nutrients are provided. Finally, we demonstrate that integration of our most highly predictive features using a probabilistic classifier resulted in accuracies surpassing any individual feature. CONCLUSION: Using features obtainable directly from sequence data, we were able to construct a classifier which can predict essential genes with high accuracy. Furthermore, our analysis of the set of genomes in which the presence of a gene is most predictive of essentiality may suggest ways in which targeted sequencing can be used in the identification of essential genes. In summary, the methods presented here can aid in the reduction of time and money invested in essential gene identification by targeting those genes for experimentation which are predicted as being essential with a high probability.

Animals↗