Biomedical subjects

Takanori Washio

Publications and source records attributed to Takanori Washio.

9 recordsLinked to original sources

PubMed2006

Characteristics and clustering of human ribosomal protein genes.

BACKGROUND: The ribosome is a central player in the translation system, which in mammals consists of four RNA species and 79 ribosomal proteins (RPs). The control mechanisms of gene expression and the functions of RPs are believed to be identical. Most RP genes have common promoters and were therefore assumed to have a unified gene expression control mechanism. RESULTS: We systematically analyzed the homogeneity and heterogeneity of RP genes on the basis of their expression profiles, promoter structures, encoded amino acid compositions, and codon compositions. The results revealed that (1) most RP genes are coordinately expressed at the mRNA level, with higher signals in the spleen, lymph node dissection (LND), and fetal brain. However, 17 genes, including the P protein genes (RPLP0, RPLP1, RPLP2), are expressed in a tissue-specific manner. (2) Most promoters have GC boxes and possible binding sites for nuclear respiratory factor 2, Yin and Yang 1, and/or activator protein 1. However, they do not have canonical TATA boxes. (3) Analysis of the amino acid composition of the encoded proteins indicated a high lysine and arginine content. (4) The major RP genes exhibit a characteristic synonymous codon composition with high rates of G or C in the third-codon position and a high content of AAG, CAG, ATC, GAG, CAC, and CTG. CONCLUSION: Eleven of the RP genes are still identified as being unique and did not exhibit at least some of the above characteristics, indicating that they may have unknown functions not present in other RP genes. Furthermore, we found sequences conserved between human and mouse genes around the transcription start sites and in the intronic regions. This study suggests certain overall trends and characteristic features of human RP genes.

Amino Acids↗

PubMed2006

Genome-wide screening of dioxin-responsive genes in fetal brain: bioinformatic and experimental approaches.

Many of the effects of dioxins, which are potent environmental pollutants and teratogens, are mediated through the aryl hydrocarbon receptor, also known as the dioxin receptor. The purpose of the present study was to characterize dioxin-responsive genes in a comprehensive manner using two complementary approaches: bioinformatic analysis and microarray analysis. First, we characterized the overall distribution of the cis-regulatory element for the dioxin-responsive element sequence (DRE) 'gcgtg' within putative promoter regions. We assembled the upstream sequences 10 kb from the transcription start site and evaluated their location and frequency in the human and mouse genomes. Second, we characterized the expression profile of mouse embryonic day 12 fetal brain exposed to 2,3,7,8-tetrarchlorodibenzo-p-dioxin. The distributions of 26,680 DREs among 2,843 human genes and 98,711 DREs among 18,541 mouse genes were examined. In both species, the DREs tended to be located close to the transcription start site. Forty genes exhibited significant induction or repression following dioxin exposure in fetal mice. The set of genes exhibited a strong functional coherence, with statistically significant enrichment in organogenesis and the DNA-dependent regulation of transcription, according to Gene Ontology annotations. In both humans and mice, DREs were preferentially distributed close to transcription start sites. Evolutionary conservation of this unique DRE distribution pattern suggests that DREs may be involved in transcriptional regulation. In mice, prenatal dioxin exposure altered the expression of 10 transcription factors, many of which have been documented to play a role in organogenesis. These genes may represent potential mediators of dioxin's effects in fetal tissues.

Animals↗

PubMed2005

GC-compositional strand bias around transcription start sites in plants and fungi.

BACKGROUND: A GC-compositional strand bias or GC-skew (=(C-G)/(C+G)), where C and G denote the numbers of cytosine and guanine residues, was recently reported near the transcription start sites (TSS) of Arabidopsis genes. However, it is unclear whether other eukaryotic species have equally prominent GC-skews, and the biological meaning of this trait remains unknown. RESULTS: Our study confirmed a significant GC-skew (C > G) in the TSS of Oryza sativa (rice) genes. The full-length cDNAs and genomic sequences from Arabidopsis and rice were compared using statistical analyses. Despite marked differences in the G+C content around the TSS in the two plants, the degrees of bias were almost identical. Although slight GC-skew peaks, including opposite skews (C < G), were detected around the TSS of genes in human and Drosophila, they were qualitatively and quantitatively different from those identified in plants. However, plant-like GC-skew in regions upstream of the translation initiation sites (TIS) in some fungi was identified following analyses of the expressed sequence tags and/or genomic sequences from other species. On the basis of our dataset, we estimated that > 70 and 68% of Arabidopsis and rice genes, respectively, had a strong GC-skew (> 0.33) in a 100-bp window (that is, the number of C residues was more than double the number of G residues in a +/-100-bp window around the TSS). The mean GC-skew value in the TSS of highly-expressed genes in Arabidopsis was significantly greater than that of genes with low expression levels. Many of the GC-skew peaks were preferentially located near the TSS, so we examined the potential value of GC-skew as an index for TSS identification. Our results confirm that the GC-skew can be used to assist the TSS prediction in plant genomes. CONCLUSION: The GC-skew (C > G) around the TSS is strictly conserved between monocot and eudicot plants (ie. angiosperms in general), and a similar skew has been observed in some fungi. Highly-expressed Arabidopsis genes had overall a more marked GC-skew in the TSS compared to genes with low expression levels. We therefore propose that the GC-skew around the TSS in some plants and fungi is related to transcription. It might be caused by mutations during transcription initiation or the frequent use of transcription factor-biding sites having a strand preference. In addition, GC-skew is a good candidate index for TSS prediction in plant genomes, where there is a lack of correlation among CpG islands and genes.

Arabidopsis↗

PubMed2005

Computational analysis suggests that alternative first exons are involved in tissue-specific transcription in rice (Oryza sativa).

MOTIVATION: Transcription start site selection and alternative splicing greatly contribute to diversifying gene expression. Recent studies have revealed the existence of alternative first exons, but most have involved mammalian genes, and as yet the regulation of usage of alternative first exons has not been clarified, especially in plants. RESULTS: We systematically identified putative alternative first exon transcripts in rice, verified the candidates using RT-PCR, and searched for the promoter elements that might regulate the alternative first exons. As a result, we detected a number of unreported alternative first exons, some of which are regulated in a tissue-specific manner. SUPPLEMENTARY INFORMATION: http://www.bioinfo.sfc.keio.ac.jp/research/intron.

Alternative Splicing↗

PubMed2005

In silico diagnosis of inherently inhibited gene expression focusing on initial codon combinations.

The translation start site, immediately downstream from the start codon, is a dominant factor for gene expression in Escherichia coli. At present, no method exists to improve the expression level of cloned genes, since it remains difficult to find the best codon combination within the region. We determined the expression parameters that correspond to all sense codons within the first four codons using GFPuv which encodes a derivative of green fluorescent protein. Using a genetic algorithm (GA)-based computer program, these parameters were incorporated in a simple, static model for the prediction of translation efficiency, and optimized to the expression level for 137 randomly isolated GFPuv genes. The calculated initial translation index (ITI), also proven for the DsRed2 gene that encodes a red fluorescent protein, should provide a solution to overcome the gene expression problem in cloned genes whose expression is often inherently blocked at the translation process. The proposed method facilitates heterologous protein production in E. coli, the most commonly used host in biological and industrial fields.

Cloning, Molecular↗

PubMed2004

Characterization of the splice sites in GT-AG and GC-AG introns in higher eukaryotes using full-length cDNAs.

For the purpose of analyzing the relation between the splice sites and the order of introns, we conducted the following analysis for the GT-AG and GC-AG splice site groups. First, the pre-mRNAs of H. sapiens, M. musculus, D. melanogaster, A. thaliana and O. sativa were sampled by mapping the full-length cDNA to the genomes. Next, the consensus sequences at different regions of pre-mRNAs were analyzed in the five species. We also investigated the mononucleotide and dinucleotide frequencies in the extensive regions around the 5' splice sites (5'ss) and 3' splice sites (3'ss). As a result, differential frequencies of nucleotides at the first 5'ss in both the GT-AG and GC-AG splice site groups were observed in A. thaliana and O. sativa pre-mRNAs. The trend, which indicates that GC 5'ss possess strong consensus sequences, was observed not only in mammalian pre-mRNAs but also in the pre-mRNAs of D. melanogaster, A. thaliana and O. sativa. Furthermore, we examined the consensus sequences of the constitutive and alternative splice sites. It was suggested that in the case of the alternative GC-AG introns, the tendency to have a weak consensus sequence at 5'ss is different between H. sapiens and M. musculus pre-mRNAs.

Animals↗

PubMed2004

Computational comparative analyses of alternative splicing regulation using full-length cDNA of various eukaryotes.

We previously reported a computational approach to infer alternative splicing patterns from Mus musculus full-length cDNA clones and microarray data. Although we predicted a large number of unreported splice variants, the general mechanisms regulating alternative splicing were yet unknown. In the present study, we compared alternative exons and constitutive exons in terms of splice-site strength and frequency of potential regulatory sequences. These regulatory features were further compared among five different species: Homo sapiens, M. musculus, Arabidopsis thaliana, Oryza sativa, and Drosophila melanogaster. Solid statistical validations of our comparative analyses indicated that alternative exons have (1) weaker splice sites and (2) more potential regulatory sequences than constitutive exons. Based on our observations, we propose a combinatorial model of alternative splicing mechanisms, which suggests that alternative exons contain weak splice sites regulated alternatively by potential regulatory sequences on the exons.

Alternative Splicing↗

PubMed2003

A novel feature of microsatellites in plants: a distribution gradient along the direction of transcription.

A computer-based analysis was conducted to assess the characteristics of microsatellites in transcribed regions of rice and Arabidopsis. In addition, two mammals were simultaneously analyzed for a comparative analysis. Our analyses confirmed a novel plant-specific feature in which there is a gradient in microsatellite density along the direction of transcription. It was also confirmed that pyrimidine-rich microsatellites are found intensively near the transcription start sites, specifically in the two plants, but not in the mammals. Our results suggest that microsatellites located at high frequency in the 5'-flanking regions of plant genes can potentially act as factors in regulating gene expression.

5' Flanking Region↗

PubMed2002

Inferring alternative splicing patterns in mouse from a full-length cDNA library and microarray data.

Although many studies on alternative splicing of specific genes have been reported in the literature, the general mechanism that regulates alternative splicing has not been clearly understood. In this study, we systematically aligned each pair of the 21,076 cDNA sequences of Mus musculus, searched for putative alternative splicing patterns, and constructed a list of potential alternative splicing sites. Two cDNAs are suspected to be alternatively spliced and originating from a common gene if they share most of their region with a high degree of sequence homology, but parts of the sequences are very distinctive or deleted in either cDNA. The list contains the following information: (1) tissue, (2) developmental stage, (3) sequences around splice sites, (4) the length of each gapped region, and (5) other comments. The list is available at http://www.bioinfo.sfc.keio.ac.jp/intron. Our results have predicted a number of unreported alternatively spliced genes, some of which are expressed only in a specific tissue or at a specific developmental stage.

Alternative Splicing↗