Project description:Chromothripsis and chromoanasynthesis are one-off catastrophic events leading to clustered genomic rearrangements. Expression profiling were performed on brain tissues with Medulloblastoma (n=9) and normal Cerebellum (n=4) to compare the expression of Double strain break DNA repair pathways.
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. SNP data from 27 and 40 primary triple negative breast cancer tumor samples from two clinical trials treated with cisplatin and cisplatin + bevacizumab. Labeling, hybridization and data processing was performed by Affymetrix using 70k MIP arrays and 330k MIP arrays. In the cisplatin trial, matched normal samples based on blood from all patients and an additional three samples based on FFPE negative lymph nodes were used as references (30 normal references in total). In the cisplatin+bevacizumab trial, mathed normal samples based on blood from 10 patients were used as references.
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:Full title: Altered levels of MOF (member of MYST family histone acetyl transferase) and decreased levels of H4K16ac correlate with a defective DNA damage response (DDR). The human MOF gene encodes a protein that specifically acetylates histone H4 at lysine 16 (H4K16ac). Here we show that altered levels of H4K16ac correlate with a defective DNA damage response (DDR) to ionizing radiation (IR). The defect however is not due to altered expression of proteins involved in DDR. Specific inhibition of H4K16ac deacetylation in MOF-depleted cells rescued IR-induced abrogation of DDR. MOF was found associated with DNA-dependent protein kinase catalytic subunit (DNAPKcs), a protein involved in non-homologous end joining (NHEJ) repair, whose ATMdependent IR-induced phosphorylation was abrogated in MOF-depleted cells. Our data indicate that MOF depletion greatly decreased the repair of DNA double-strand breaks (DSBs) by NHEJ and homologous recombination (HR). In addition, the MOF protein activity associates with chromatin upon DNA damage and colocalizes with the synaptonemal complex in male meiocytes. We propose that MOF, through H4K16ac, plays a critical role in the cellular DNA damage response. Keywords: Cell type comparison HEK293 cells were transfected with plasmids encoding hMOF for over-expression of the histone acetyl transferase that leads to elevated levels of acetylation of Lysine 16 of histone H4. siRNA mediated knock-down of hMOF was performed to deplete the H4K16ac levels. Total RNA samples for expression profiling was obtained from wild type (293 cells without any treatment), hMOF over-expressed and hMOF knock-down 293 cell lines. Each sample was analyzed in triplicates using EGPF dsRNA treated samples as control.
Project description:Full title: Altered levels of MOF (member of MYST family histone acetyl transferase) and decreased levels of H4K16ac correlate with a defective DNA damage response (DDR). The human MOF gene encodes a protein that specifically acetylates histone H4 at lysine 16 (H4K16ac). Here we show that altered levels of H4K16ac correlate with a defective DNA damage response (DDR) to ionizing radiation (IR). The defect however is not due to altered expression of proteins involved in DDR. Specific inhibition of H4K16ac deacetylation in MOF-depleted cells rescued IR-induced abrogation of DDR. MOF was found associated with DNA-dependent protein kinase catalytic subunit (DNAPKcs), a protein involved in non-homologous end joining (NHEJ) repair, whose ATMdependent IR-induced phosphorylation was abrogated in MOF-depleted cells. Our data indicate that MOF depletion greatly decreased the repair of DNA double-strand breaks (DSBs) by NHEJ and homologous recombination (HR). In addition, the MOF protein activity associates with chromatin upon DNA damage and colocalizes with the synaptonemal complex in male meiocytes. We propose that MOF, through H4K16ac, plays a critical role in the cellular DNA damage response. Keywords: Cell type comparison
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:Senescent cells are a major cause of organismal aging and a key target for anti-aging therapies. Persistent DNA damage signaling is a primary driver of the induction and maintenance of cellular senescence. However, many DNA damaging stimuli that induce senescence, such as irradiation or transient exposure to genotoxic drugs, are transient. The mechanisms underlying persistent damage signaling in senescent cells, and why senescent cells fail to repair damaged DNA, remain unknown. Here, we were able to assess the mechanisms underlying persistence of DNA damage and senescence maintenance by designing a precisely controllable senescence system that does not require potent stressors to induce senescence. We demonstrate that sustained mTORC1 signaling in senescent cells causes gradually accumulating DNA damage and an inflammatory response that maintains cell-cycle arrest. Markedly, activation of E2F transcription, which promotes expression of DNA repair proteins, can reverse accumulated DNA damage. Thus, persistent DNA damage signaling arises in senescent cells by uncoupling of mTORC1 and E2F signaling, whereby prolonged mTORC1 activity causes gradually increasing DNA damage that cannot be sufficiently repaired without induction of protective E2F target genes.