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SNP microarray of T-REx-293-based clones overexpressing the DNA cytosine deaminase APOBEC3B

ABSTRACT: A conditional and isogenic system for APOBEC3B (A3B) induction in T-REx-293 cells. Cells were engineered to express doxycycline-inducible A3B-eGFP or eGFP constructs and subjected to 10 rounds of A3B-eGFP exposure causing 80-90% cell death. Control pools (eGFP) were subjected to parallel rounds of non-toxic eGFP exposure, and dilutions were done each round to mimic A3B-eGFP induced population fluctuations. DNA was extracted and subjected to SNP analyses using the Human OmniExpress-24v1-0 BeadChip (Illumina, San Diego, CA). Genotyping was performed using the humanomniexpress_24v1-0_a cluster file.

ORGANISM(S): Homo sapiens

PROVIDER: GSE78710 | GEO | 2016/06/30

SECONDARY ACCESSION(S): PRJNA314329

REPOSITORIES: GEO

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SNP microarray of T-REx-293-based clones overexpressing the DNA cytosine deaminase APOBEC3B

Project description:A conditional and isogenic system for APOBEC3B (A3B) induction in T-REx-293 cells. Cells were engineered to express doxycycline-inducible A3B-eGFP or eGFP constructs and subjected to 10 rounds of A3B-eGFP exposure causing 80-90% cell death. Control pools (eGFP) were subjected to parallel rounds of non-toxic eGFP exposure, and dilutions were done each round to mimic A3B-eGFP induced population fluctuations. DNA was extracted and subjected to SNP analyses using the Human OmniExpress-24v1-0 BeadChip (Illumina, San Diego, CA). Genotyping was performed using the humanomniexpress_24v1-0_a cluster file. SNP data is avaiable for a total of 16 samples, all derived from single cells mother lines A and C. For each series, each consisting of 8 samples, A3B-eGFP and eGFP daugther clones were processed on the SNP microarray, as well as 3 A3B-eGFP and 3 eGFP grand-daugther clones.

2016-06-30 | E-GEOD-78710 | biostudies-arrayexpress

The RB/E2F pathway controls expression of the cancer genomic DNA deaminase APOBEC3B

Project description:Mutations in cancer are due in part to DNA cytosine deamination by APOBEC3B (A3B). While low in healthy tissues, A3B expression and activity are elevated in tumors and further increase in metastases. However, molecular mechanisms responsible for A3B transcriptional regulation are poorly understood. Here, we address whether the RB/E2F pathway, which is often dysregulated in breast cancer, is a molecular trigger of A3B overexpression. First, an A3B promoter-driven luciferase reporter was used to demonstrate reporter activation by disruption of only one out of five predicted E2F binding sites. Second, A3B-luciferase reporter activation was also triggered by expressing the BK polyomavirus T-antigen, which inactivates RB and thereby alleviates repression of E2F regulated genes. Importantly, A3B-luciferase reporter induction by BK polyomavirus T-antigen could not be further increased by mutating the functional E2F binding site. Third, both CRISPR disruption and targeted base substitutions in the endogenous E2F binding site caused strong A3B upregulation and confirmed importance of this regulatory element. Fourth, proteomics experiments showed that members of the DREAM and PRC1.6-complexes including multiple E2F family members are able to bind to wild-type but not E2F mutant promoter sequences. Finally, a combination of genetic and biochemical studies implicated E2F4 and E2F6 in endogenous A3B gene repression. Altogether, our studies demonstrate that A3B expression is suppressed in normal cells by the RB/E2F axis and that viral or mutational disruption of this pathway causes overexpression of this DNA deaminase in cancer and contributes mutational fuel to tumor evolution.

2020-10-19 | PXD020473 | Pride

R-loop homeostasis and cancer mutagenesis promoted by the DNA cytosine deaminase APOBEC3B

Project description:The single-stranded DNA cytosine-to-uracil deaminase APOBEC3B is an antiviral protein implicated in cancer. However, its substrates in cells are not fully delineated. Here, APOBEC3B proteomics reveal interactions with a surprising number of R-loop factors. Biochemical experiments show APOBEC3B binding to R-loops in human cells and in vitro. Genetic experiments demonstrate R-loop increases in cells lacking APOBEC3B and decreases in cells overexpressing APOBEC3B. Genome-wide analyses show major changes in the overall landscape of physiological and stimulus-induced R-loops with thousands of differentially altered regions as well as binding of APOBEC3B to many of these sites. APOBEC3 mutagenesis impacts overexpressed genes and splice factor mutant tumors preferentially, and APOBEC3-attributed kataegis are enriched in RTCW consistent with APOBEC3B deamination. Taken together with the fact that APOBEC3B binds single-stranded DNA and RNA and preferentially deaminates DNA, these results support a mechanism in which APOBEC3B mediates R-loop homeostasis and contributes to R-loop mutagenesis in cancer.

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Project description: Not available

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Project description: Not available

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Conformational Switch Regulates the DNA Cytosine Deaminase Activity of Human APOBEC3B.