Towards genome-engineering in complex cyanobacterial communities: RNA-guided transposition in Anabaena
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PROVIDER: PRJEB60371 | ENA |
REPOSITORIES: ENA
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Project description:In genome engineering, the integration of incoming DNA has been dependent on enzymes produced by dividing cells, which has been a bottleneck toward increasing DNA insertion frequencies and accuracy. Recently, RNA-guided transposition with CRISPR-associated transposase (CAST) was reported as highly effective and specific in Escherichia coli. Here, we developed Golden Gate vectors to test CAST in filamentous cyanobacteria and to show that it is effective in Anabaena sp. strain PCC 7120. The comparatively large plasmids containing CAST and the engineered transposon were successfully transferred into Anabaena via conjugation using either suicide or replicative plasmids. Single guide (sg) RNA encoding the leading but not the reverse complement strand of the target were effective with the protospacer-associated motif (PAM) sequence included in the sgRNA. In four out of six cases analyzed over two distinct target loci, the insertion site was exactly 63 bases after the PAM. CAST on a replicating plasmid was toxic, which could be used to cure the plasmid. In all six cases analyzed, only the transposon cargo defined by the sequence ranging from left and right elements was inserted at the target loci; therefore, RNA-guided transposition resulted from cut and paste. No endogenous transposons were remobilized by exposure to CAST enzymes. This work is foundational for genome editing by RNA-guided transposition in filamentous cyanobacteria, whether in culture or in complex communities.
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Project description:Bacterial transposons are pervasive mobile genetic elements that exploit distinct DNA binding proteins for their horizontal spread. For example, E. coli Tn7 homes to a specific attachment site using a TniQ family protein, whereas diverse Tn7-like transposons employ Type I or Type V CRISPR-Cas systems to insert downstream of target sites specified by a guide RNA. Despite this targeting pathway diversity, transposition invariably requires TnsB, a DDE superfamily transposase that catalyses DNA excision and insertion, and TnsC, a AAA+ ATPase that is thought to communicate between the transposase and targeting proteins. How TnsC mediates this communication and thereby regulates transposition fidelity has remained elusive. Here we apply chromatin immunoprecipitation sequencing (ChIP-seq) to monitor in vivo formation of the Vibrio cholerae RNA-guided transpososome, allowing us to unambiguously resolve distinct protein recruitment events prior to integration. DNA targeting by the TniQ-Cascade complex is surprisingly promiscuous, leading to binding at hundreds of genomic off-target sites, but only a subset of those sites are licensed for TnsC and TnsB recruitment, revealing a crucial proofreading checkpoint that controls transposition fidelity. To advance the mechanistic understanding of interactions responsible for transpososome assembly, we analysed V. cholerae TnsC by cryo-EM and found that TnsC forms ATP-dependent heptameric rings, which are likely to play a critical architectural role in positioning DNA substrates for downstream integration. Collectively, our results highlight the molecular specificity imparted by consecutive binding of distinct factors to genomic target sites during RNA-guided transposition, and provide a structural roadmap to guide future engineering efforts.
2021-10-31 | GSE183114 | GEO
Project description:RNA-guided endonucleases form the crux of diverse biological processes and technologies, including adaptive immunity, transposition, and genome editing. Some of these enzymes are components of insertion sequences (IS) in the IS200/IS605 and IS607 transposon families. Both IS families encode a TnpA transposase and TnpB nuclease, an RNA-guided enzyme ancestral to CRISPR-Cas12. In eukaryotes and their viruses, TnpB homologs occur as two distinct types, Fanzor1 and Fanzor2. We analyzed the evolutionary relationships between prokaryotic TnpBs and eukaryotic Fanzors, revealing that a clade of IS607 TnpBs with unusual active site arrangement found primarily in cyanobacteria likely gave rise to both types of Fanzors. The widespread nature of Fanzors imply that the properties of this particular group of IS607 TnpBs were particularly suited to adaptation and evolution in eukaryotes and their viruses. Biochemical analysis of a prokaryotic IS607 TnpB and virally encoded Fanzor1s revealed features that may have fostered co-evolution between TnpBs/Fanzors and their cognate transposases. These results provide insight into the evolutionary origins of a ubiquitous family of RNA-guided proteins that shows remarkable conservation across the three domains of life.
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Project description:The goal of these experiments was to define the targets of Ty3 transposition in Saccharomyces cerevisiae. Ty3 is a retroviruslike element that is found at the transcription initiation site of chromosomal tRNA genes. A Ty3 that can be induced by growth in galactose-containing medium and which was marked by an insertion of HIS3 downstream of the second open reading frame of the element (POL3) was induced to undergo transposition by plating cells onto galactose containing medium and replica-plating onto medium selective for cells that had undergone transposition. These cells were collected, DNA was extracted, and inverse PCR was performed using primers inside the Ty3 element in order to generate a library of insertion sites flanked by Illumina sequence-compatible primers.
2011-09-02 | E-GEOD-31820 | biostudies-arrayexpress
Project description:Selective recruitment of the AAA+ ATPase TnsC increases the fidelity of Type I-F CRISPR RNA-guided transposition
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Project description:Transposable elements (TEs) are genomic parasite that threat genome integrity. One major strategy organisms evolved to balance TE activity in the germline is the Piwi-interacting RNAs (piRNAs) pathway. It prevents transposition by repressing TE at transcriptional and/or post-transcriptional level. However, evidence that TE derepression caused by piRNA pathway impairment is actually followed by bursts of transposition is still lacking. Here we present a genome-wide TE-analyses of the replicative TE life cycle (their expression, their translation to their transposition in the germline) after piRNA pathway impairment in the somatic follicle cells. We observed a high transposition-rate in the germline, leading to a 10-fold increase in genomic TE-load after 70 successive generations of piRNA pathway impairment. Moreover, we demonstrate that siRNAs co-regulate TE activity at post transcriptional level in follicle cells. These observations demonstrate that the small RNA-mediated TE repression in follicle cells contribute to genome homeostasis.
2018-08-09 | GSE112966 | GEO
Project description:Transposable elements (TEs) are genomic parasite that threat genome integrity. One major strategy organisms evolved to balance TE activity in the germline is the Piwi-interacting RNAs (piRNAs) pathway. It prevents transposition by repressing TE at transcriptional and/or post-transcriptional level. However, evidence that TE derepression caused by piRNA pathway impairment is actually followed by bursts of transposition is still lacking. Here we present a genome-wide TE-analyses of the replicative TE life cycle (their expression, their translation to their transposition in the germline) after piRNA pathway impairment in the somatic follicle cells. We observed a high transposition-rate in the germline, leading to a 10-fold increase in genomic TE-load after 70 successive generations of piRNA pathway impairment. Moreover, we demonstrate that siRNAs co-regulate TE activity at post transcriptional level in follicle cells. These observations demonstrate that the small RNA-mediated TE repression in follicle cells contribute to genome homeostasis.
2018-08-09 | GSE112925 | GEO
Project description:Transposable elements (TEs) are genomic parasite that threat genome integrity. One major strategy organisms evolved to balance TE activity in the germline is the Piwi-interacting RNAs (piRNAs) pathway. It prevents transposition by repressing TE at transcriptional and/or post-transcriptional level. However, evidence that TE derepression caused by piRNA pathway impairment is actually followed by bursts of transposition is still lacking. Here we present a genome-wide TE-analyses of the replicative TE life cycle (their expression, their translation to their transposition in the germline) after piRNA pathway impairment in the somatic follicle cells. We observed a high transposition-rate in the germline, leading to a 10-fold increase in genomic TE-load after 70 successive generations of piRNA pathway impairment. Moreover, we demonstrate that siRNAs co-regulate TE activity at post transcriptional level in follicle cells. These observations demonstrate that the small RNA-mediated TE repression in follicle cells contribute to genome homeostasis.
2018-08-09 | GSE112971 | GEO
Project description:Transposable elements (TEs) are genomic parasite that threat genome integrity. One major strategy organisms evolved to balance TE activity in the germline is the Piwi-interacting RNAs (piRNAs) pathway. It prevents transposition by repressing TE at transcriptional and/or post-transcriptional level. However, evidence that TE derepression caused by piRNA pathway impairment is actually followed by bursts of transposition is still lacking. Here we present a genome-wide TE-analyses of the replicative TE life cycle (their expression, their translation to their transposition in the germline) after piRNA pathway impairment in the somatic follicle cells. We observed a high transposition-rate in the germline, leading to a 10-fold increase in genomic TE-load after 70 successive generations of piRNA pathway impairment. Moreover, we demonstrate that siRNAs co-regulate TE activity at post transcriptional level in follicle cells. These observations demonstrate that the small RNA-mediated TE repression in follicle cells contribute to genome homeostasis.
2018-08-09 | GSE112968 | GEO