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Expanding the catalog of cas genes with metagenomes.

ABSTRACT: The CRISPR (clusters of regularly interspaced short palindromic repeats)-Cas adaptive immune system is an important defense system in bacteria, providing targeted defense against invasions of foreign nucleic acids. CRISPR-Cas systems consist of CRISPR loci and cas (CRISPR-associated) genes: sequence segments of invaders are incorporated into host genomes at CRISPR loci to generate specificity, while adjacent cas genes encode proteins that mediate the defense process. We pursued an integrated approach to identifying putative cas genes from genomes and metagenomes, combining similarity searches with genomic neighborhood analysis. Application of our approach to bacterial genomes and human microbiome datasets allowed us to significantly expand the collection of cas genes: the sequence space of the Cas9 family, the key player in the recently engineered RNA-guided platforms for genome editing in eukaryotes, is expanded by at least two-fold with metagenomic datasets. We found genes in cas loci encoding other functions, for example, toxins and antitoxins, confirming the recently discovered potential of coupling between adaptive immunity and the dormancy/suicide systems. We further identified 24 novel Cas families; one novel family contains 20 proteins, all identified from the human microbiome datasets, illustrating the importance of metagenomics projects in expanding the diversity of cas genes.

SUBMITTER: Zhang Q

PROVIDER: S-EPMC3936711 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Expanding the catalog of cas genes with metagenomes.

Zhang Quan Q Doak Thomas G TG Ye Yuzhen Y

Nucleic acids research 20131206 4

The CRISPR (clusters of regularly interspaced short palindromic repeats)-Cas adaptive immune system is an important defense system in bacteria, providing targeted defense against invasions of foreign nucleic acids. CRISPR-Cas systems consist of CRISPR loci and cas (CRISPR-associated) genes: sequence segments of invaders are incorporated into host genomes at CRISPR loci to generate specificity, while adjacent cas genes encode proteins that mediate the defense process. We pursued an integrated app ...[more]

PMID: 24319142

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Project description:While the majority of protein-coding genes in the human genome have been identified, the location of the regulatory sequences that control their expression in time and space remains poorly defined. The importance of identifying these elements is underscored by a growing number of studies (such as GWAS) supporting a relationship between variation in non-coding sequences and human disease. M-BM- emonstrated that ChIP-Seq with p300 directly on human or mouse tissues represents a powerful method to identify the location and tissue-specific activity pattern of enhancers in the genome.M-BM- a highly specific chromatin mark for the prediction of in vivo enhancers, it is not without limitations. M-BM- comparison of p300-bound regions with previously generated enhancer sets shows that the majority of enhancers are activated independently of p300. To attempt to identify a larger proportion of enhancers in vivo, we have focused on several additional transcriptional coactivators that are hypothesized to be associated with active tissue-specific enhancers. M-BM- limited availability of ChIP-seq grade antibodies for these coactivators, FLAG-tag knock-in mice were generated and ChIP-seq using a FLAG antibody was performed on various tissues from e11.5 mouse embryos. Indeed, as these mouse lines have become available we have validated their valuable role as marks for transcriptional enhancers in vivo.M-BM- studies are expected to further expand the catalogue of in vivo functional enhancers, which will aid in the decoding of the regulatory genome and provide new insights into the role of gene regulation in human biology and disease. In addition to FLAG data, this accession includes histone acetylation / methylation ChIP-seq data from e11.5 mouse embryonic tissues. Histone ChIP-seq data was used in combination with FLAG data for various computational analyses. Examination of FLAG-labeled transcriptional coactivator binding in mouse embryonic stage 11.5 and embryonic stem cells

Project description:BackgroundMetagenome sampling bias for geographical location and lifestyle is partially responsible for the incomplete catalog of reference genomes of gut microbial species. Thus, genome assembly from currently under-represented populations may effectively expand the reference gut microbiome and improve taxonomic and functional profiling.MethodsWe assembled genomes using public whole-metagenomic shotgun sequencing (WMS) data for 110 and 645 fecal samples from India and Japan, respectively. In addition, we assembled genomes from newly generated WMS data for 90 fecal samples collected from Korea. Expecting genome assembly for low-abundance species may require a much deeper sequencing than that usually employed, so we performed ultra-deep WMS (> 30 Gbp or > 100 million read pairs) for the fecal samples from Korea. We consequently assembled 29,082 prokaryotic genomes from 845 fecal metagenomes for the three under-represented Asian countries and combined them with the Unified Human Gastrointestinal Genome (UHGG) to generate an expanded catalog, the Human Reference Gut Microbiome (HRGM).ResultsHRGM contains 232,098 non-redundant genomes for 5414 representative prokaryotic species including 780 that are novel, > 103 million unique proteins, and > 274 million single-nucleotide variants. This is an over 10% increase from the UHGG. The new 780 species were enriched for the Bacteroidaceae family, including species associated with high-fiber and seaweed-rich diets. Single-nucleotide variant density was positively associated with the speciation rate of gut commensals. We found that ultra-deep sequencing facilitated the assembly of genomes for low-abundance taxa, and deep sequencing (e.g., > 20 million read pairs) may be needed for the profiling of low-abundance taxa. Importantly, the HRGM significantly improved the taxonomic and functional classification of sequencing reads from fecal samples. Finally, analysis of human self-antigen homologs on the HRGM species genomes suggested that bacterial taxa with high cross-reactivity potential may contribute more to the pathogenesis of gut microbiome-associated diseases than those with low cross-reactivity potential by promoting inflammatory condition.ConclusionsBy including gut metagenomes from previously under-represented Asian countries, Korea, India, and Japan, we developed a substantially expanded microbiome catalog, HRGM. Information of the microbial genomes and coding genes is publicly available ( www.mbiomenet.org/HRGM/ ). HRGM will facilitate the identification and functional analysis of disease-associated gut microbiota.

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Expanding the catalog of cas genes with metagenomes.

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Expanding the catalog of cas genes with metagenomes.

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