Mechanisms of extreme genomic instability at large transcribed genes
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ABSTRACT:
PROVIDER: PRJNA647482 | ENA |
REPOSITORIES: ENA
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Project description:Mechanisms of extreme genomic instability at large transcribed genes
| PRJNA647481 | ENA
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Project description:Human alkyladenine DNA glycosylase (AAG) initiates base excision repair (BER) to guard against mutations by excising alkylated and deaminated purines. Counterintuitively, increased expression of AAG has been implicated in increased rates of spontaneous mutation in microsatellite repeats. This microsatellite mutator phenotype is consistent with a model in which AAG excises bulged (unpaired) bases, altering repeat length. To directly test the role of base excision in AAG-induced mutagenesis, we conducted mutation accumulation experiments in yeast overexpressing different variants of AAG and detected mutations via high-depth genome resequencing. We also developed a new software tool, hp_caller, to perform accurate genotyping at homopolymeric repeat loci. Overexpression of wild-type AAG elevated indel mutations in homopolymeric sequences distributed throughout the genome. However, catalytically inactive variants (E125Q/E125A) caused equal or greater increases in frameshift mutations. These results disprove the hypothesis that base excision is the key step in mutagenesis by overexpressed wild-type AAG. Instead, our results provide additional support for the previously published model wherein overexpressed AAG interferes with the mismatch repair (MMR) pathway. In addition to the above results, we observed a dramatic mutator phenotype for N169S AAG, which has increased rates of excision of undamaged purines. This mutant caused a 10-fold increase in point mutations at G:C base pairs and a 50-fold increase in frameshifts in A:T homopolymers. These results demonstrate that it is necessary to consider the relative activities and abundance of many DNA replication and repair proteins when considering mutator phenotypes, as they are relevant to the development of cancer and its resistance to treatment.
| S-EPMC5363859 | biostudies-literature
Project description:Extreme Environments Genome sequencing and assembly
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Project description:P53 independent P21 expression deregulates replication licensing , leading to genomic instability
2016-05-17 | PXD004140 | Pride
Project description:Repetitive sequences are hotspots of evolution at multiple levels. However, due to technical difficulties involved in their assembly and analysis, the role of repeats in tumor evolution is poorly understood. We developed a rigorous motif-based methodology to quantify variations in the repeat content of proteomes and genomes, directly from proteomic and genomic raw sequence data, and applied it to analyze a wide range of tumors and normal tissues. We identify high similarity between the repeat-instability in tumors and their patient-matched normal tissues, but also tumor-specific signatures, both in protein expression and in the genome, that strongly correlate with cancer progression and robustly predict the tumorigenic state. In a patient, the hierarchy of genomic repeat instability signatures accurately reconstructs tumor evolution, with primary tumors differentiated from metastases. We find an inverse relationship between repeat-instability and point mutation load, within and across patients, and independently of other somatic aberrations. Thus, repeat-instability is a distinct, transient and compensatory adaptive mechanism in tumor evolution.
2020-06-02 | PXD012574 | Pride
Project description:Studies of genomic instability have historically focused on intrinsic mechanisms rather than extrinsic mechanisms based in the tumor microenvironment (TME). TGF-β is the most abundantly secreted cytokine in the TME where it imparts various aggressive characteristics including invasive migration, drug resistance and epithelial-to-mesenchymal transition (EMT). Here we show that TGF-β also promotes genomic instability in the form of DNA double strand breaks (DSB) in cancer cells which lack the tumor suppressor gene RUNX3. Loss of RUNX3 resulted in transcriptional downregulation of the redox regulator heme oxygenase-1 (HO-1 or HMOX1). Consequently, elevated oxidative DNA damage disrupted genomic integrity and triggered cellular senescence, which was accompanied by tumor-promoting inflammatory cytokine expression and acquisition of the senescence-associated secretory phenotype (SASP). Recapitulating the above findings, tumors harbouring a TGF-β gene expression signature and RUNX3 loss exhibited higher levels of genomic instability. In summary, RUNX3 creates an effective barrier against further TGF-β-dependent tumor progression by preventing genomic instability. These data suggest a novel cooperation between cancer cell-extrinsic TGF-β signaling and cancer cell-intrinsic RUNX3 inactivation as aggravating factors for genomic instability.
2019-06-20 | GSE133037 | GEO
Project description:We used genome-wide microarray comparative genomic hybridization to investigate the response of control HT1080 cells and HT1080 cells infected with a lentivirus expressing eGFP, GLI2-eGFP or CCND1-RFP to challenge with methotrexate to address the question if GLI2 overexpression induces genomic instability. Keywords: aCGH
2009-01-06 | GSE10132 | GEO