Genome Network Project: An Integrated Genomic Platform

With the objective of elucidating the structure of gene interactions in the human genome, the Genome Network Project has generated a vast quantity of experimental data, mainly focusing on transcriptional control and transcription-factor related protein-protein interactions (PPI). This data has been collected and organized into the Genome Network Platform ("http://genomenetwork.nig.ac.jp/":http://genomenetwork.nig.ac.jp/) at the National Institute of Genetics. Expression data was obtained through CAGE (Cap Analysis Gene Expression), qRT-PCR, tiling array, microarray and short RNA analysis, while PPI information was gathered through yeast two hybrid (Y2H), mammalian two hybrid (M2H) and _in vitro_ virus (IVV) methods. The Genome Network Platform Viewer provides an integrated user interface to the complete database, including services of gene search, whole genome browsing, PPI network viewer, and expression profile analysis. Our platform represents an extremely useful resource for researchers in the field of genomics, and provides access to high quality data through the combination of intuitive browsing and visualization capabilities

Monotreme-Specific Conserved Putative Proteins Derived from Retroviral Reverse Transcriptase

Endogenous retroviruses (ERVs) have played an essential role in the evolution of mammals. ERV-derived genes are reported in the therians, many of which are involved in placental development; however, the contribution of the ERV-derived genes in monotremes, which are oviparous mammals, remains to be uncovered. Here, we conducted a comprehensive search for possible ERV-derived genes in platypus and echidna genomes and identified three reverse transcriptase-like genes named RTOM1, RTOM2, and RTOM3 clustered in the GRIP2 intron. Comparative genomic analyses revealed that RTOM1, RTOM2, and RTOM3 are strongly conserved and are under purifying selection between these species. These could be generated by tandem duplications before the divergence of platypus and echidna. All RTOM transcripts were specifically expressed in the testis, possibly suggesting their physiological importance. This is the first study reporting monotreme-specific de novo gene candidates derived from ERVs, which provides new insights into the unique evolution of monotremes

An ancient retroviral RNA element hidden in mammalian genomes and its involvement in co-opted retroviral gene regulation

哺乳類のゲノムに隠された古代ウイルス --古代ウイルス特有の遺伝子制御機構の発見--. 京都大学プレスリリース. 2021-11-10.[Background] Retroviruses utilize multiple unique RNA elements to control RNA processing and translation. However, it is unclear what functional RNA elements are present in endogenous retroviruses (ERVs). Gene co-option from ERVs sometimes entails the conservation of viral cis-elements required for gene expression, which might reveal the RNA regulation in ERVs. [Results] Here, we characterized an RNA element found in ERVs consisting of three specific sequence motifs, called SPRE. The SPRE-like elements were found in different ERV families but not in any exogenous viral sequences examined. We observed more than a thousand of copies of the SPRE-like elements in several mammalian genomes; in human and marmoset genomes, they overlapped with lineage-specific ERVs. SPRE was originally found in human syncytin-1 and syncytin-2. Indeed, several mammalian syncytin genes: mac-syncytin-3 of macaque, syncytin-Ten1 of tenrec, and syncytin-Car1 of Carnivora, contained the SPRE-like elements. A reporter assay revealed that the enhancement of gene expression by SPRE depended on the reporter genes. Mutation of SPRE impaired the wild-type syncytin-2 expression while the same mutation did not affect codon-optimized syncytin-2, suggesting that SPRE activity depends on the coding sequence. [Conclusions] These results indicate multiple independent invasions of various mammalian genomes by retroviruses harboring SPRE-like elements. Functional SPRE-like elements are found in several syncytin genes derived from these retroviruses. This element may facilitate the expression of viral genes, which were suppressed due to inefficient codon frequency or repressive elements within the coding sequences. These findings provide new insights into the long-term evolution of RNA elements and molecular mechanisms of gene expression in retroviruses

Potentially reduced fusogenicity of syncytin‐2 in New World monkeys

Syncytin-2 is a membrane fusion protein involved in placenta development that is derived from the endogenous retrovirus envelope gene acquired in the common ancestral lineage of New World and Old World monkeys. It is known that syncytin-2 is conserved between apes and Old World monkeys, suggesting its functional importance; however, syncytin-2 of common marmosets (Callithrix jacchus) exhibits lower fusogenic activity than those of humans and Old World monkeys in human cell lines. To obtain insight into the functional diversity of syncytin-2 genes in primates, we examined the syncytin-2 gene in New World monkeys. We experimentally evaluated the cell fusion ability of syncytin-2 in humans, C. jacchus, and tufted capuchins (Sapajus apella). We found that the cell fusion ability of S. apella was lower than that of human syncytin-2. Chimeric syncytin-2 constructs revealed that the amino acid differences in the surface unit of S. apella syncytin-2 were responsible for the weak cell fusion activity. In addition, genomic sequence analyses of syncytin-2 revealed that the open reading frames (ORFs) of syncytin-2 were highly conserved in 7 apes and 22 Old World monkeys; however, the syncytin-2 ORFs of three out of 12 New World monkey species were truncated. Our results suggest that syncytin-2 in several New World monkeys may be of less importance than in Old World monkeys and apes, and other syncytin-like genes may be required for placental development in various New World monkey species

Preliminary Report of the Waseda University Excavations at Dahshur North:Tenth Season,2004-2005

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A description of the structural determination procedures of a gap junction channel at 3.5 Å resolution

The structural determination procedures of a gap junction channel at 3.5 Å resolution are described, including the preparation of crystals, intensity data collection, data processing, phasing and structural refinement

DNA-Binding Specificity Changes in the Evolution of Forkhead Transcription Factors

The evolution of transcriptional regulatory networks entails the expansion and diversification of transcription factor (TF) families. The forkhead family of TFs, defined by a highly conserved winged helix DNA-binding domain (DBD), has diverged into dozens of subfamilies in animals, fungi, and related protists. We have used a combination of maximum-likelihood phylogenetic inference and independent, comprehensive functional assays of DNA-binding capacity to explore the evolution of DNA-binding specificity within the forkhead family. We present converging evidence that similar alternative sequence preferences have arisen repeatedly and independently in the course of forkhead evolution. The vast majority of DNA-binding specificity changes we observed are not explained by alterations in the known DNA-contacting amino acid residues conferring specificity for canonical forkhead binding sites. Intriguingly, we have found forkhead DBDs that retain the ability to bind very specifically to two completely distinct DNA sequence motifs.We propose an alternate specificity-determining mechanism whereby conformational rearrangements of the DBD broaden the spectrum of sequence motifs that a TF can recognize. DNA-binding bispecificity suggests a previously undescribed source of modularity and flexibility in gene regulation and may play an important role in the evolution of transcriptional regulatory networks.Organismic and Evolutionary Biolog

Diversity of preferred nucleotide sequences around the translation initiation codon in eukaryote genomes

Understanding regulatory mechanisms of protein synthesis in eukaryotes is essential for the accurate annotation of genome sequences. Kozak reported that the nucleotide sequence GCCGCC(A/G)CCAUGG (AUG is the initiation codon) was frequently observed in vertebrate genes and that this ‘consensus’ sequence enhanced translation initiation. However, later studies using invertebrate, fungal and plant genes reported different ‘consensus’ sequences. In this study, we conducted extensive comparative analyses of nucleotide sequences around the initiation codon by using genomic data from 47 eukaryote species including animals, fungi, plants and protists. The analyses revealed that preferred nucleotide sequences are quite diverse among different species, but differences between patterns of nucleotide bias roughly reflect the evolutionary relationships of the species. We also found strong biases of A/G at position −3, A/C at position −2 and C at position +5 that were commonly observed in all species examined. Genes with higher expression levels showed stronger signals, suggesting that these nucleotides are responsible for the regulation of translation initiation. The diversity of preferred nucleotide sequences around the initiation codon might be explained by differences in relative contributions from two distinct patterns, GCCGCCAUG and AAAAAAAUG, which implies the presence of multiple molecular mechanisms for controlling translation initiation