Sequence-specific toxicity of dCas9 in bacteria
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PROVIDER: PRJEB45922 | ENA |
REPOSITORIES: ENA
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Project description:Infinium MethylationEPIC (850K) BeadChip data for wildtype SUM159 cells (2 replicates), SUM159 cells transfected with plV-KRAB (dCas9 CRISPRi system; 3 replicates), and SUM159 cells transfected with dCas9-KRAB and 4 targeting gRNAs against the ZEB1 promoter (3 replicates)
2023-04-17 | GSE210273 | GEO
Project description:We report the generation of CRISPR-dCas9 DNA methyltransferases to mediate targeted DNA methylation. Using the dCas9-BFP-DNMT3A and dCas9-BFP-DNMT3B methyltransferases, we have demonstrated that these two methyltransferase can mediate targeted methylation in three human genes tested: uPA, TGFBR3, and CDKN2A in human HEK293T cells. We also showed that these methyltransferases could mediate gene inhibition. five samples co-transfected with five uPA sgRNAs and each of the four dCas9 fusions, or control transfection with pUC19 plasmid
2016-06-01 | E-GEOD-74935 | biostudies-arrayexpress
Project description:Background: The CRISPR/Cas9 toolbox has recently been expanded to include approaches for modulating gene expression. To successfully build on this work, and apply it for answering biological questions, it is important to establish it in a broad range of circumstances. Genome-scale CRISPR interference (CRISPRi) has been used in human cells lines, however the rules for designing effective guide RNAs (gRNAs) in different organisms are not well known. We sought to determine rules that determine gRNA effectiveness at transcriptional repression in Saccharomyces cerevisiae. Results: We created an inducible single plasmid CRISPRi system for gene repression in yeast, and used it to analyze fitness effects of gRNAs under 18 small molecule treatments. Our approach correctly identified previously-described chemical-genetic interactions, as well as a new mechanism of suppressing fluconazole toxicity by repression of the ERG25 gene. Assessment of multiple target loci across treatments allowed us to determine generalizable features associated with gRNA efficacy. Guides that target regions with low nucleosome occupancy and high chromatin accessibility were clearly more effective. We also found the best region to target gRNAs was between the transcription start site (TSS) and 200bp upstream of the TSS. Finally, unlike nuclease-proficient Cas9 in human cells, point mutations were tolerated equally well by truncated (18 nt specificity sequence) and full length (20 nt) gRNAs, however, 18 nt gRNAs were generally less potent than full length gRNAs. Conclusions: Our results establish a powerful functional genomics screening method, provide rules for designing effective gRNAs for gene repression, and show that 18 nt and 20 nt gRNAs exhibit similar tolerance to mismatches in the target sequence. These findings will enable effective library design and genome-wide screening in many genetic backgrounds. An expression construct was created for inducible CRISPRi in yeast. Key features include ORFs expressing dCas9-Mxi1 and the tetracycline repressor (TetR), as well as a tetracycline inducible gRNA locus containing the RPR1 promoter with a TetO site, a NotI site for cloning new gRNA specificity sequences, and the constant part of the gRNA. When yeast containing this plasmid are grown in the absence of anhydrotetracycline (ATc) TetR binds the gRNA promoter and prevents PolIII from binding and transcribing the gRNA. This in turn prevents dCas9-Mxi1 from binding the target site. In the presence of ATc, TetR dissociates and gRNA is expressed, allowing dCas9-Mxi1 to bind its target locus, and repress gene expression. gRNA libraries were cloned into this construct and transformed into yeast to create pools. Experiments were conducted in which yeast pools were grown in inducing (+ATc) and non-inducing conditions (-ATc) in the presence of different drugs. After multiple generations of growth in these conditions, yeast plasmids were minipreped and the gRNA locus was PCRed and sequenced via MiSeq. Counts of each gRNA were compared in different conditions.
2016-01-18 | E-GEOD-71490 | biostudies-arrayexpress
Project description:Transcriptional profiling of mouse embryonic stem cells comparing control (dCas9 transfected) ES cells with ES cells transfected with a Hottip promoter gRNAs and Hoxa13 promoter gRNAs along with dCAs9-VP160. Goal was to determine the effects of activation of Hottip lncRNA and Hoxa13 on expression of Hox genes
2017-03-10 | GSE95064 | GEO
Project description:RNA-Seq after Cas9-gRNA transfection with different length gRNAs we performed PolyA Selection and RNA-Seq on cells transfected with dCas9-VPR and a gRNA of each length (20nt, 16nt, or 14nt) targeting ACTC1, MIAT, or HBG1/2
2015-07-15 | E-GEOD-70694 | biostudies-arrayexpress
Project description:Over the last decade, gene-silencing mediated by dCas9 binding to transcribed regions or their promoters, a strategy referred to as CRISPRi, has emerged as a powerful tool in bacterial genetics. While this strategy has already been broadly adopted, several studies have reported experimental setups in which dCas9 expression was toxic. In particular, guide RNAs that share specific PAM-proximal sequence motifs were shown to be toxic to E. coli. Here we demonstrate that this toxicity is caused by off-target binding of dCas9 to the promoter of essential genes. Silencing of off-target genes can occur with as little as 4nt of identity between the PAM-proximal sequence and the off-target position. This phenomenon only occurs in some promoter sequences but does not appear to be constrained to any specific PAM-proximal sequence. Accordingly, screens performed in various strains of E. coli and related species shows that the nature of toxic guide RNAs changes together with the evolution of the sequence of off-target positions. These results highlight the importance of relying on several guide RNAs targeting the same gene when performing CRISPRi experiments in bacteria in order to avoid any possible confounding results due to off-target binding.
2022-10-25 | GSE216032 | GEO
Project description:Over the last decade, gene-silencing mediated by dCas9 binding to transcribed regions or their promoters, a strategy referred to as CRISPRi, has emerged as a powerful tool in bacterial genetics. While this strategy has already been broadly adopted, several studies have reported experimental setups in which dCas9 expression was toxic. In particular, guide RNAs that share specific PAM-proximal sequence motifs were shown to be toxic to E. coli. Here we demonstrate that this toxicity is caused by off-target binding of dCas9 to the promoter of essential genes. Silencing of off-target genes can occur with as little as 4nt of identity between the PAM-proximal sequence and the off-target position. This phenomenon only occurs in some promoter sequences but does not appear to be constrained to any specific PAM-proximal sequence. Accordingly, screens performed in various strains of E. coli and related species shows that the nature of toxic guide RNAs changes together with the evolution of the sequence of off-target positions. These results highlight the importance of relying on several guide RNAs targeting the same gene when performing CRISPRi experiments in bacteria in order to avoid any possible confounding results due to off-target binding.
2022-11-04 | GSE217004 | GEO
Project description:Fusion of active protein domains to the nuclease-deficient clustered regularly interspaced short palindromic repeat (CRISPR) associated protein 9 (dCas9) has been widely used for epigenome editing, but the specificities of these engineered proteins have still not been fully investigated. Targeted methylation of specific gene loci offers a direct approach to perturb DNA methylation-associated biological processes. In this study, we generated and validated the global off-target characteristics of CRISPR-guided DNA methyltransferases (CRISPRme) by fusing the catalytic domain of DNMT3A or DNMT3B to the C terminus of the dCas9 protein from S. pyogenes. Using targeted quantitative bisulfite pyrosequencing and whole genome bisulfite sequencing (WGBS), we prove that CRISPRme can efficiently methylate the CpG dinucleotides flanking its target sites in genomic loci (uPA and TGFBR3) in human cells (HEK293T) with CpG-methylation levels exceeding 70% for some target sites. Using qPCR, fluorescent reporter cells, and RNA sequencing, we found that CRISPRme can mediate transient inhibition of gene expression which appears to result from Cas9-mediated interference with transcription rather than de novo DNA methylation. Analyses of whole genome methylation did not identify global methylation changes, however a substantial number of CRISPRme off-target differentially methylated regions (DMR, over 6000) were still identified. The majority of these DMRs were hypermethylated both in cells expressing CRISPRme alone and cells expressing CRISPRme together with gRNAs. These off-target hypermethylated sites were enriched in gene bodies, introns, 5’UTR, CGI shores, Alu sequences, open chromatin and PAM rich regions, but not correlated with off-target binding sites predicted by ChIP-seq. Our results prove that CRISPRme allows for efficient RNA-guided methylation of endogenous CpGs, however with high frequencies of off-target methylation indicating that further improvements of the specificity of CRISPR-dCas9 based DNA methylation modifiers are still required.
2016-12-14 | GSE92310 | GEO
Project description:Epigenetic aberration is one of the major driving factors in the initiation, promotion, and progression of human cancer and it is also often associated with acquired therapeutic resistance. Several chemical epigenetic modulators have been reported. However, results from animal models and clinical trials have indicated that severe on- and off-target toxicity is one of the leading factors behind failures in epidrug development. CRISPR/dCas9 technology provides a powerful tool for precise epigenetic regulation at the single-gene level. This approach requires ectopic expression of exogenous epigenetic modulatory proteins, which cause side effects and technical challenges for preparation and delivery. Recently, we have shown that Cas9 tagging with the peptide motif (FCPF) was recognized by perfluoro biphenyl derivatives. Here, we introduced the FCPF-tag into dCas9 and report a chemically induced platform for epigenome editing (Chem-CRISPR/dCas9FCPF). By conjugating JQ1, a BRD4 inhibitor, to perfluoro biphenyl (JQ1-FCPF), we demonstrate that JQ1-FCPF covalently binds to CRISPR/dCas9 and specifically inhibits BRD4 in proximity to the promoters/enhancers of c-MYC with the guidance of c-MYC sgRNAs. Thus, we achieved epigenetic modulation of c-MYC with high efficiency and specificity.
2023-06-09 | GSE232132 | GEO
Project description:Fusion of active protein domains to the nuclease-deficient clustered regularly interspaced short palindromic repeat (CRISPR) associated protein 9 (dCas9) has been widely used for epigenome editing, but the specificities of these engineered proteins have still not been fully investigated. Targeted methylation of specific gene loci offers a direct approach to perturb DNA methylation-associated biological processes. In this study, we generated and validated the global off-target characteristics of CRISPR-guided DNA methyltransferases (CRISPRme) by fusing the catalytic domain of DNMT3A or DNMT3B to the C terminus of the dCas9 protein from S. pyogenes. Using targeted quantitative bisulfite pyrosequencing and whole genome bisulfite sequencing (WGBS), we prove that CRISPRme can efficiently methylate the CpG dinucleotides flanking its target sites in genomic loci (uPA and TGFBR3) in human cells (HEK293T) with CpG-methylation levels exceeding 70% for some target sites. Using qPCR, fluorescent reporter cells, and RNA sequencing, we found that CRISPRme can mediate transient inhibition of gene expression which appears to result from Cas9-mediated interference with transcription rather than de novo DNA methylation. Analyses of whole genome methylation did not identify global methylation changes, however a substantial number of CRISPRme off-target differentially methylated regions (DMR, over 6000) were still identified. The majority of these DMRs were hypermethylated both in cells expressing CRISPRme alone and cells expressing CRISPRme together with gRNAs. These off-target hypermethylated sites were enriched in gene bodies, introns, 5’UTR, CGI shores, Alu sequences, open chromatin and PAM rich regions, but not correlated with off-target binding sites predicted by ChIP-seq. Our results prove that CRISPRme allows for efficient RNA-guided methylation of endogenous CpGs, however with high frequencies of off-target methylation indicating that further improvements of the specificity of CRISPR-dCas9 based DNA methylation modifiers are still required.
2016-12-14 | GSE92261 | GEO