ALC1 and PARP activities coordinate chromatin accessibility and viability in homologous recombination deficient cells (RNA-seq)
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ABSTRACT:
PROVIDER: PRJNA627391 | ENA |
REPOSITORIES: ENA
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Project description:The response to Poly (ADP-ribose) polymerase inhibitors (PARPi) is dictated by homologous recombination (HR) DNA repair mechanisms and the abundance of lesions that trap PARP enzymes on chromatin. It remains unclear, however, if the established role of PARP in promoting chromatin accessibility impacts viability in these settings. Using a CRISPR based screen, we identify the PAR-binding Snf2-like ATPase, ALC1 as a key determinant of PARPi toxicity in HR-deficient cells. ALC1 loss reduced viability of BRCA mutant cells and enhanced their sensitivity to PARPi by up to 250-fold, while overcoming several known resistance mechanisms. ALC1 loss was not epistatic to other repair pathways that execute the PARPi response. Instead, ALC1 deficiency reduced chromatin accessibility concomitant with a decrease in the association of repair factors. This resulted in an accumulation of replication associated DNA damage and a reliance on HR. These findings establish PAR-dependent chromatin remodeling as a mechanistically distinct aspect of PARPi responses, implicating ALC1 inhibition as a new approach to overcome therapeutic resistance in HR-deficient cancers.
2020-12-02 | GSE149104 | GEO
Project description:The response to Poly (ADP-ribose) polymerase inhibitors (PARPi) is dictated by homologous recombination (HR) DNA repair mechanisms and the abundance of lesions that trap PARP enzymes on chromatin. It remains unclear, however, if the established role of PARP in promoting chromatin accessibility impacts viability in these settings. Using a CRISPR based screen, we identify the PAR-binding Snf2-like ATPase, ALC1 as a key determinant of PARPi toxicity in HR-deficient cells. ALC1 loss reduced viability of BRCA mutant cells and enhanced their sensitivity to PARPi by up to 250-fold, while overcoming several known resistance mechanisms. ALC1 loss was not epistatic to other repair pathways that execute the PARPi response. Instead, ALC1 deficiency reduced chromatin accessibility concomitant with a decrease in the association of repair factors. This resulted in an accumulation of replication associated DNA damage and a reliance on HR. These findings establish PAR-dependent chromatin remodeling as a mechanistically distinct aspect of PARPi responses, implicating ALC1 inhibition as a new approach to overcome therapeutic resistance in HR-deficient cancers.
2020-12-02 | GSE150955 | GEO
Project description:ALC1 and PARP activities coordinate chromatin accessibility and viability in homologous recombination deficient cells (ATAC-seq)
| PRJNA634143 | ENA
Project description:BRCA1 deficiencies cause breast, ovarian and other cancers, and render tumours hypersensitive to PARP-inhibitors. To understand resistance mechanisms, we conducted whole-genome CRISPR-Cas9 synthetic-viability/resistance screens in BRCA1-deficient breast cancer cells treated with PARP-inhibitors. Thus, we identified two previously uncharacterized proteins, C20orf196 and FAM35A, whose inactivation confers strong PARP-inhibitor resistance. Mechanistically, we show that C20orf196 and FAM35A form a complex, termed “Shieldin” (SHLD1/2), with FAM35A interacting with single-stranded DNA via its C-terminal OB-fold region. We establish that Shieldin promotes DNA double-strand break (DSB) end-joining, acting as the downstream effector of 53BP1/RIF1/MAD2L2 to restrict DSB resection and counteract homologous recombination in BRCA1-deficient cells by antagonising BRCA2/RAD51 loading. Notably, Shieldin inactivation further sensitises BRCA1-deficient cells to cisplatin, suggesting how defining the SHLD1/2 status of BRCA1-deficient tumours might aid patient stratification and yield new treatment opportunities. Highlighting this potential, we document reduced SHLD1/2 expression in human breast cancers displaying intrinsic or acquired PARP-inhibitor resistance.
2018-05-31 | PXD009830 | Pride
Project description:Sister chromatid exchanges (SCEs) are a product of joint DNA molecules resolution, and are considered to require homologous recombination (HR). Canonical HR factors BRCA1, BRCA2 and RAD51 were indeed essential for SCE induction in response to irradiation-induced DNA breaks. By contrast, replication-blocking agents, including PARP inhibitors, induced SCEs independently of BRCA1, BRCA2 or RAD51. HR-independent SCEs were associated with incomplete DNA replication, as evidenced by post-replicative single-stranded DNA (ssDNA) accumulation and enrichment of PARP inhibitor-induced SCEs at common fragile sites (CFSs). Importantly, PARP-induced DNA lesions were transmitted into mitosis, pointing towards SCEs originating from mitotic processing of underreplicated DNA. We found polymerase theta to be associated to mitotic DNA lesions, to be required for SCE formation and to prevent chromosome fragmentation upon PARP inhibition in HR-defective cells. Combined, our data show that replication-blocking agents lead to underreplicated DNA in mitosis, which is processed into SCEs independently of canonical HR factors.
2023-03-11 | PXD028670 | Pride
Project description:Preclinical data support the investigation of PARP inhibitors in other neoplasms exhibiting homologous recombination deficiency (HRD) as monotherapy as well as in combination with chemotherapy. However，in colorectal cancer (CRC), the role of HRD alterations is mostly unknown. This study aims to explore the the Efficacy and Safety of Fluzoparib combined with Irinotecan in the Second-line treatment of HRD alterations metastatic colorectal cancer.
| 8652 | ecrin-mdr-crc
Project description:Colorectal Cancer (CRC) is a leading cause of cancer-related death. Around 30% of patients present with advanced disease and 50% of those that attempt curative surgery will eventually relapse. The potential synergism of combining PARP inhibitor and PD-L1 is based on the hypothesis that pharmacological inhibition of PARP by olaparib will result in enhanced immunogenicity which can be further enhanced with an immune checkpoint inhibitor such as pembrolizumab. This may occur through a number of mechanisms, such as increased production of cytokines and chemokines that have the potential to promote antitumour immunity, upregulation of surface receptors which render tumour cells more visible to detection by cytotoxic T cells thereby leading to death of tumour cells and release of neoantigens, that help promote antigen presentation and immune priming. This hypothesis is supported by preclinical studies in mouse models of cancer, demonstrating that administration of a PARP inhibitor to sensitive tumour types resulted in increased T cell infiltration and immune activation within tumours.
The primary hypothesis is that Olaparib and pembrolizumab combination will lead to an increase in objective response rate in patients with refractory metastatic colorectal cancer (mCRC) with DNA homologous-recombination-repair deficiency (HRD) from 1.5% in benchmark studies to up to >10%. The primary objective of the study is to determine the objective response rate (ORR) of pembrolizumab in combination with olaparib, assessed by the investigator per RECIST criteria version 1.1. Secondary objectives include efficacy in terms of disease control rate (DCR), progression-free survival (PFS), overall survival (OS) and duration of response (DOR); safety and an exploratory study of biomarkers associated with treatment efficacy and disease prognosis.
| 2401742 | ecrin-mdr-crc
Project description:Brca1 is required for DNA repair by homologous recombination (HR) and normal embryonic development. Here we report that deletion of the DNA damage responsefactor 53BP1 overcomes embryonic lethality in Brca1-nullizygous mice, and rescues HR deficiency, as measured by hypersensitivity to PARP (polyADPribose polymerase) inhibition. However, Brca1,53BP1 double-deficient cells are hypersensitive to DNA interstrand crosslinks (ICLs), indicating that BRCA1 has an additional role in DNA cross-link repair that is distinct from HR. Disruption of the non-homologous end-joining (NHEJ) factor, Ku, promotes DNA repair in Brca1-deficient cells; however deletion of either Ku or 53BP1 exacerbates genomic instability in cells lacking FANCD2, a mediator of the Fanconi Anemia pathway for ICL repair. Brca1 therefore has two separate roles in ICL repair, whereas FANCD2 provides a key activity that can not be bypassed by ablation of 53BP1 or Ku. B cells were stimulated to undergo class switch recombination in vitro. Chromatin from B cells was harvested 72 hours post-stimulation and used for RPA ChIP to study the extent of resection of DNA DSBs.
2012-09-30 | E-GEOD-35698 | biostudies-arrayexpress
Project description:Poly(ADP-ribose) Polymerase 1 (PARP-1) is a nuclear enzyme that catalyse the transfer of ADP-ribose units from NAD+ to several target proteins involved in cellular stress responses. Using the cell line WRL68, we have previously shown that the activation of PARP-1 induced by oxidative stress after H2O2 treatment lead to depletion of cellular NAD+ and ATP, which promote cell death. In this work, we used LC-MS/MS based phosphoproteomics to show that the oxidative damage induced by H2O2 treatment modified the phosphorylation of several proteins in WRL68 cells, most of them related to transcription process. Interestingly, genetic or pharmacological inhibition of PARP-1 reduced the phosphorylation of YAP1, a transcriptional coactivator involved in cell survival, in WRL68 cells after H2O2 treatment. Inhibition of PARP-1 increased cell viability after oxidative treatment and diminished the degradation of YAP1; the elimination of YAP1 by gene silencing abrogated the protective effect of PARP-1 inhibition, indicating that YAP1 is important for the survival of WRL68 cells after oxidative damage. In the same way, the supplementation of NAD+, substrate of PARP-1, on WRL68 cells suffering oxidative damage reduced the phosphorylation of YAP1, suggesting that the loss of cellular NAD+ caused by PARP-1 activation after oxidative treatment is responsible for the phosphorylation of YAP1. Finally, PARP-1 silencing after oxidative treatment diminished the activation of AMPK, a master regulator of cell metabolism implicated in the restoration of energy balance during metabolic stress. Since NAD+ supplementation reduced the phosphorylation of some AMPK substrates in WRL68 cells after oxidative treatment, we hypothesize that the loss of cellular NAD+ after PARP-1 activation may induce a metabolic stress that activates AMPK. In summary, we showed a new crucial role of PARP-1 in the response to oxidative stress in WRL68 cells; PARP-1 activation reduces the cell viability by promoting the phosphorylation and degradation of YAP1, which is mediated by the energy stress caused by PARP-1 activation.
2020-12-18 | PXD019823 | Pride
Project description:The inhibitor of DNA-binding 3 (ID3) is a transcriptional regulator that limits interaction of basic helix-loop-helix transcription factors with their target DNA sequences. We previously reported that ID3 loss is associated with mutational signatures linked to DNA repair defects. Here we demonstrate that ID3 exhibits a dual role to promote DNA double-strand break (DSB) repair, particularly homologous recombination (HR). ID3 interacts with the MRN complex and RECQL helicase to activate DSB repair and it facilitates RAD51 loading and downstream steps of HR. In addition, ID3 promotes the expression of HR genes in response to ionizing radiation by regulating both chromatin accessibility and activity of the transcription factor E2F1. Consistently, analyses of TCGA cancer patient data demonstrate that low ID3 expression is associated with impaired HR. The loss of ID3 leads to sensitivity of tumor cells to PARP inhibition, offering new therapeutic opportunities in ID3-deficient tumors.
2022-02-17 | PXD028946 | Pride