Homo sapiens isolate:HEK293T
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA544942 | ENA |
REPOSITORIES: ENA
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Project description:APOBEC-AID family of cytidine deaminase prefers single-stranded nucleic acids for cytidine to uracil deamination. Single-stranded nucleic acids are commonly involved in the DNA repair system for breaks generated by CRISPR-Cas9. Here, we show in human cells that APOBEC3s can trigger the cytidine deamination of single-stranded oligodeoxynucleotides, which ultimately results in base substitution mutations in genomic DNA through the homology-directed repair (HDR) of Cas9-generated double-strand breaks . In addition, the APOBEC3-catalyzed deamination in genomic single-stranded DNA formed during the repair of Cas9 nickase-generated single-strand breaks can be further processed to yield mutations mainly involving insertions or deletions (indels). Mechanistically, both APOBEC3-mediated deamination and DNA repair proteins play important roles in the generation of these indels. Correspondingly, optimizing conditions for the repair of CRISPR-Cas9-generated DNA breaks, such as using double-stranded donors in HDR or temporarily suppressing endogenous APOBEC3s, can substantially repress these unwanted mutations in genomic DNA.
2017-11-10 | GSE105146 | GEO
Project description:The RNA-guided DNA endonuclease Cas9 has emerged as a powerful new tool for genome engineering. Cas9 creates targeted double-strand breaks (DSBs) in the genome. Knock-in of specific mutations (precision genome editing) requires homology-directed repair (HDR) of the DSB by synthetic donor DNAs containing the desired edits, but HDR has been reported to be variably efficient. Here, we report that linear DNAs (single and double-stranded) engage in a high-efficiency HDR mechanism that requires only ~35 nucleotides of homology with the targeted locus to introduce edits ranging from 1 to 1000 nucleotides. We demonstrate the utility of linear donors by introducing fluorescent protein tags in human cells and mouse embryos using PCR fragments. We find that repair is local, polarity-sensitive, and prone to template switching, characteristics that are consistent with gene conversion by synthesis-dependent strand-annealing (SDSA). Our findings enable rational design of synthetic donor DNAs for efficient genome editing.
2017-12-01 | GSE107546 | GEO
Project description:Saturation Editing of Genomic Regions by Multiplex Homology Directed Repair
| PRJNA254528 | ENA
Project description:Poly [ADP-ribose] polymerase 1 (PARP1) is involved in differentiation, proliferation, tumor transformation, in repair of single-stranded DNA and double-stranded DNA breaks (DSBs) in conjunction with BRCA. PARP1 enzyme works modifying nuclear proteins by poly ADP-ribosylation. It was found that PARP1 and HNRNPA2B1 bind at termini of forum domains and may play a role in coordinated regulation of genes in forum domains (Tchurikov et al., 2013). Forum domains are long DNA fragments of excised chromosomal DNA. Mostly forum domains are of 50-200 kb in length, although larger domains, up to 500 - 700 kb, are also observed. The domains are delimited by hot spots of double-strand breaks (DSBs). This ChIP-Seq is aimed to compare genome-wide binding sites of PARP1 with different genomic features, including the hot spots of DSBs.
2017-02-01 | GSE74954 | GEO
Project description:DNA methyltransferases (DNMTs) are thought to be involved in the cellular response to DNA damage, thus linking DNA repair mechanisms with DNA methylation. This study presents a novel method of targeted DNA methylation that utilizes endogenous DNA double strand break repair pathways and applies it to the neurodegenerative disease gene C9orf72. A double strand break induced by CRISPR/cas9 in the promoter of C9orf72 is sufficient to induce DNA methylation, and methylation can be precisely targeted through the process of homology directed repair (HDR) via delivery of an in vitro methylated exogenous repair template. Long methylated double stranded DNA templates induce more methylation than shorter templates and with higher efficiency than a dCas9-DNMT3a fusion protein construct. Genome-wide methylation analysis reveals no significant off-target methylation changes when inducing methylation via HDR, whereas the dCas9-DNMT3a fusion construct causes significant off-target methylation at over 67,000 sites. This method is applied to generate a patient derived iPSC model of amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD) that exhibits stable DNA methylation patterns similar to those seen in patients. Using this model, it’s shown for the first time that DNA methylation of the 5’ regulatory region directly reduces C9orf72 expression and increases histone H3K9 tri-methylation levels.
2019-10-11 | GSE134995 | GEO
Project description:DNA methyltransferases (DNMTs) are thought to be involved in the cellular response to DNA damage, thus linking DNA repair mechanisms with DNA methylation. This study presents a novel method of targeted DNA methylation that utilizes endogenous DNA double strand break repair pathways and applies it to the neurodegenerative disease gene C9orf72. A double strand break induced by CRISPR/cas9 in the promoter of C9orf72 is sufficient to induce DNA methylation, and methylation can be precisely targeted through the process of homology directed repair (HDR) via delivery of an in vitro methylated exogenous repair template. Long methylated double stranded DNA templates induce more methylation than shorter templates and with higher efficiency than a dCas9-DNMT3a fusion protein construct. Genome-wide methylation analysis reveals no significant off-target methylation changes when inducing methylation via HDR, whereas the dCas9-DNMT3a fusion construct causes significant off-target methylation at over 67,000 sites. This method is applied to generate a patient derived iPSC model of amyotrophic lateral sclerosis and frontotemporal dementia (ALS/FTD) that exhibits stable DNA methylation patterns similar to those seen in patients. Using this model, it’s shown for the first time that DNA methylation of the 5’ regulatory region directly reduces C9orf72 expression and increases histone H3K9 tri-methylation levels.
2019-10-11 | GSE134994 | GEO
Project description:Kinetics and fidelity of the repair of Cas9-induced double-strand DNA breaks
| PRJNA450382 | ENA
Project description:Aberrant end joining of DNA double strand breaks leads to chromosomal rearrangements and to insertion of nuclear or mitochondrial DNA into breakpoints, which is commonly observed in cancer cells and constitutes a major threat to genome integrity. However, the mechanisms that are causative for these insertions are largely unknown. By monitoring end joining of different linear DNA substrates introduced into HEK293 cells, as well as by examining end joining of CRISPR/Cas9 induced DNA breaks in HEK293 and HeLa cells, we provide evidence that the dNTPase activity of SAMHD1 impedes aberrant DNA resynthesis at DNA breaks during DNA end joining. Hence, SAMHD1 expression or low intracellular dNTP levels lead to shorter repair joints and impede insertion of distant DNA regions prior end repair. Our results reveal a novel role for SAMHD1 in DNA end joining and provide new insights into how loss of SAMHD1 may contribute to genome instability and cancer development.
2021-01-20 | E-MTAB-8382 | biostudies-arrayexpress
Project description:Homologous recombination (HR) is crucial for genetic exchange, accurate repair of DNA double-strand breaks and pivotal for genome integrity. HR uses homologous sequences for repair, but how homology search, the exploration of the genome for homologous DNA sequences, is conducted in the nucleus remains poorly understood. Here, we use time-resolved chromatin immunoprecipitations of repair proteins to monitor homology search in vivo. We found that homology search proceeds by a probing mechanism, which commences around the break and samples preferentially on the broken chromosome. However, elements thought to instruct chromosome loops mediate homology search shortcuts, and centromeres, which cluster within the nucleus, may facilitate homology search on other chromosomes. Our study thus revealed crucial parameters for homology search in vivo and emphasizes the importance of linear distance, chromosome architecture and proximity for recombination efficiency. 2 new custom ChIP-chip platforms used; both Nimblegen; differ in oligo density: (platform 1: 2006-07-18_Scerevisiae_ChIP_Stefan Jentsch MPI Biochemistry S.cerevisiae 385K Tiling Array Version 1) ( platform 2: 100304_Scer2_MS_Chip_Stefan Jentsch MPI Biochemistry S.cerevisiae 135K Tiling Array Version 2) ChIP-chip profiling of DSB repair factors (Rad51, Rad52, RPA, gamma-H2A) upon single inducible DSBs in S.cerevisiae
2013-03-21 | E-GEOD-44844 | biostudies-arrayexpress