Project description:Targetted metabolomics in U2OS PRDX1 WT and PRDX1-/- While cellular metabolism impacts the DNA damage response, a systematic understanding of the metabolic requirements that are crucial for DNA damage repair has yet to be achieved. Here, we investigate the metabolic enzymes and processes that are essential when cells are exposed to DNA damage. By integrating functional genomics with chromatin proteomics and metabolomics, we provide a detailed description of the interplay between cellular metabolism and the DNA damage response. Subsequent analysis identified Peroxiredoxin 1, PRDX1, as fundamental for DNA damage repair. During the DNA damage response, PRDX1 translocates to the nucleus where it is required to reduce DNA damage-induced nuclear reactive oxygen species levels. Moreover, PRDX1 controls aspartate availability, which is required for the DNA damage repair-induced upregulation of de novo nucleotide synthesis. Loss of PRDX1 leads to an impairment in the clearance of γΗ2ΑΧ nuclear foci, accumulation of replicative stress and cell proliferation defects, thus revealing a crucial role for PRDX1 as a DNA damage surveillance factor.
Project description:RNA splicing and the DNA damage response are intriguingly linked in mammals but the underlying mechanisms remain poorly understood. Using an in vivo biotinylation tagging approach in mice we show that XAB2, the human homologue of the yeast pre-mRNA-splicing factor SYF1 has a functional role in Nucleotide Excision Repair (NER) and the DNA damage response (DDR) in mammals. XAB2 interacts with spliceosome factors and is part of the core spliceosome that binds to spliceosomal U4 and U6 snRNAs during hepatic development. Ablation of XAB2 leads to defective NER, intron retention, the aberrant accumulation of pre-mRNAs and to a faulty ATM/ATR DDR signaling. Using functional approaches, we find that XAB2 dissociates from RNA targets upon persistent DNA damage or transcription blockage and from spliceosomal RNAs in the NER-defective developing livers. Thus, XAB2 functionally links NER to the spliceosomal response to DNA damage during hepatic development with important ramifications for transcription-coupled DNA repair disorders.
Project description:We investigated how yeast cells deficient in performing homologous recombination-mediated DNA repair due to a deletion of the critical RAD52 gene respond to irreparable DNA damage inflicted by genotoxic treatment commonly applied in cancer therapy (camptothecin and irradiation). We found that upon persistence of irreparable DNA damage, yeast rad52 mutants readily undergo checkpoint adaptation accompanied by the acquisition of resistance to further genotoxic insults as well as the development of aneuploidy. Together, our findings can be used to elucidate how repair-defective cancer cells can become treatment-resistant thereby providing a way to target these resistant cell clones by tackling their aneuploidy-associated phenotypes. To investigate these characteristics commonly present in aneuploid cells in our experimental set-up, we treated yeast cells with genotoxic agents and performed whole genome sequencing. We could identify frequent whole chromosome loss events manifesting in a sensitivity of cells to aneuploidy-targeting agents.
Project description:Cornelia de Lange Syndrome is a multisystem developmental disorder typically caused by mutations in the gene encoding the cohesin loader NIPBL. The associated phenotype is generally assumed to be the consequence of aberrant transcriptional regulation. Recently, we identified a residue substitution in BRD4 associated with a Cornelia de Lange-like Syndrome, that reduces BRD4 binding to acetylated histones. Here we show that, although this mutation reduces BRD4-enhancer interaction in mouse embryonic stem cells, it does not affect transcription. Rather it delays the cell cycle, increased DNA damage signalling, and perturbs regulation of DNA repair in mutant cells. This uncovers a new role for BRD4 in DNA repair pathway choice. Furthermore, we find evidence of a similar increase in DNA damage signalling in cells derived from NIPBL-deficient individuals, suggesting that defective DNA damage signalling and repair is also a feature of typical Cornelia de Lange Syndrome.
Project description:Determining the balance between DNA double strand break repair (DSBR) pathways is essential for understanding treatment response in cancer. We report a novel method for simultaneously measuring non-homologous end joining (NHEJ), homologous recombination (HR), and microhomology-mediated end joining (MMEJ). This approach revealed enhanced MMEJ and HR in glioblastoma (GBM) xenograft models with acquired temozolomide (TMZ) resistance. Knockdown of proteins in either pathway enhanced killing by TMZ, and a targeted screen identified pharmacological-grade dual HR/MMEJ inhibitors, including AZD1390, an ATM kinase inhibitor. AZD1390 suppressed DSB end resection, blocked phosphorylation of end protection proteins in response to DNA damage, and potentiated TMZ in treatment-naïve and treatment-resistant models. TP53-mutant GBMs were most susceptible to AZD1390 in combination with DNA-damaging agents due to elevated ATM-dependent HR/MMEJ, preferential activation of these pathways in response to DNA damage, and a defective G2/M checkpoint, which caused these GBMs to enter mitosis despite unrepaired DNA damage, leading to cell death via apoptosis. This report establishes ATM-dependent HR and MMEJ as targetable resistance mechanisms in TP53-mutant GBM and establishes an approach for simultaneously measuring multiple DSBR pathways in treatment selection and oncology research.
Project description:DNA repair competency is one determinant of sensitivity to certain chemotherapy drugs, such as cisplatin. Cancer cells with intact DNA repair can avoid the accumulation of genome damage during growth and also can repair platinum-induced DNA damage. We sought genomic signatures indicative of defective DNA repair in cell lines and tumors and correlated these signatures to platinum sensitivity. The number of subchromosomal regions with allelic imbalance extending to the telomere (NtAI) predicted cisplatin sensitivity in vitro and pathologic response to preoperative cisplatin treatment in patients with triple-negative breast cancer (TNBC). In serous ovarian cancer treated with platinum-based chemotherapy, higher levels of NtAI forecast a better initial response. We found an inverse relationship between BRCA1 expression and NtAI in sporadic TNBC and serous ovarian cancers without BRCA1 or BRCA2 mutation. Thus, accumulation of telomeric allelic imbalance is a marker of platinum sensitivity and suggests impaired DNA repair.
Project description:Endogenous aldehydes induce inter-strand crosslinks (ICL) and DNA-protein crosslinks (DPC). While DNA-repair and aldehyde-clearance systems cope with cellular toxicity, deficiencies in these mechanisms cause genome-instability disorders. The FA-pathway, defective in Fanconi anemia (FA), specifically removes ICL. In contrast, SPRTN, compromised in Ruijs-Aalfs syndrome, eliminates DPC during replication. However, AMeDS patients lacking aldehyde-detoxification display combined features of FA and Cockayne syndrome, associated with transcription-coupled repair (TCR) deficiency, suggesting a novel repair mechanism for aldehyde-induced DNA lesions in active genes. In this report, we demonstrate efficient resolution of aldehyde-induced transcription-blocking lesions by TCR. Mass-spectrometry and DPC-seq identify the TCR complex and additional factors involved in DPC removal and formaldehyde-induced damage tolerance. Notably, TFIIS-dependent cleavage of stalled-RNAPII transcripts exclusively protects against formaldehyde-induced damage. A mouse-model lacking both aldehyde-clearance and TCR pathways confirms endogenous DPC accumulation in transcribed regions. These findings highlight the importance of DPC removal in preventing transcription-roadblocks and contribute to understanding disorders related to aldehyde clearance and TCR deficiencies.
Project description:Zygotic repair of paternal genome is a key event after fertilization. Spermatozoa accumulate DNA single and double strand breaks during spermatogenesis and can suffer additional damage before fertilization by different factors, including cryopreservation. Fertilization with DNA damaged spermatozoa (DDS) is considered to promote implantation failures and abortions, but also long term effects in the progeny that could be related to a defective repair. Base excision repair (BER) pathway is considered the most active in zygotic DNA repair, but healthy oocytes contain enzymes for all repairing pathways. In this study the effects of the inhibition of the BER pathway in the zygote, were analyzed on the progeny obtained after fertilization with differentially DDS. Massive gene expression (37.394 transcripts) was analyzed after hatching using microarrays. Trout oocytes are easily fertilized with DDS and the high prolificacy allows obtaining live progeny even with a high rate of abortions. Results showed that DDS, even if increased the number of abortions, provided normal progeny. Nevertheless, the zygotic inhibition of PARP, upstream the BER pathway, result 810 differentially expressed genes (DEGs) after hatching. DEGs are related to DNA repair, apoptosis, telomere maintenance or growth and development, revealing a scenario of impaired DNA damage signalization and repair. Down-regulation of the apoptotic cascade was noticed, suggesting a selection of embryos tolerant to residual DNA damage during embryo development. Our results suggest a high zygotic capacity to repair paternal DNA damage and reveals changes in the progeny from defective repairing zygotes whose long term consequences should be deeply analyzed Gene expression was analyzed in trout larvae one day after hatching obtained from differentially DNA damaged sperm with or without zygotic inhibition of the BER pathway of DNA repair. Eggs from two females were pooled and fertilized with sperm fresh (F samples) or cryopreserved using different procedures (LDL and EY samples). Ten min later two batches from each sperm kind were treated with 3-aminobenzamide (3AB) to inhibit the PARP activity. Ten larvae per each one of the 6 treatments (3sperm kind x 2 zygotic treatments) were analyzed after pooling RNA. Four replicates per treatment were done fertilizing eggs from the same females with sperm from 4 different males.