CRISRP screens reveal determinants of PARP inhibitor response in prostate cancer
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA781904 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR16983321.fastq.gz | Fastqsanger.gz | |||
| SRR16983322.fastq.gz | Fastqsanger.gz | |||
| SRR16983323.fastq.gz | Fastqsanger.gz | |||
| SRR16983324.fastq.gz | Fastqsanger.gz | |||
| SRR16983325.fastq.gz | Fastqsanger.gz |
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Project description:Prostate cancer harboring BRCA1/2 mutations are often exceptionally sensitive to PARP inhibitors. However, genomic alterations in other DNA damage response genes have not been consistently predictive of clinical response to PARP inhibition. Here, we perform genome-wide CRISPR-Cas9 knockout screens in BRCA1/2-proficient prostate cancer cells and identify previously unknown genes whose loss has a profound impact on PARP inhibitor response. Specifically, MMS22L deletion, frequently observed (up to 14%) in prostate cancer, renders cells hypersensitive to PARP inhibitors by disrupting RAD51 loading required for homologous recombination repair, although this response is TP53-dependent. Unexpectedly, loss of CHEK2 confers resistance rather than sensitivity to PARP inhibition through increased expression of BRCA2, a target of CHEK2-TP53-E2F7-mediated transcriptional repression. Combined PARP and ATR inhibition overcomes PARP inhibitor resistance caused by CHEK2 loss. Our findings may inform the use of PARP inhibitors beyond BRCA1/2-deficient tumors and support reevaluation of current biomarkers for PARP inhibition in prostate cancer.
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Project description:PARP inhibitors (PARPi) present a remarkable advance in the treatment of patients with homologous recombination (HR)-deficient tumors but resistance remains a challenge1-5. While most research has focused on the downstream consequences of PARPi exposure to tackle resistance, the immediate impact of PARP inhibition on the chromatin environment and its contribution to PARPi toxicity remains elusive. Here, we show that PARP inhibition induces histone release from the chromatin. This presents a vulnerability of PARPi-resistant cancer cells, which are addicted to histone homeostasis mechanisms to sustain elevated DNA replication rates and survival. Through functional genetic screens, we identified NASP as a key factor in maintaining the stability of evicted histones via its TPR motifs. NASP loss renders tumor cells hypersensitive to PARPi treatment in vitro and in vivo, impairs replication fork progression and elevates levels of replication-associated DNA damage. Moreover, NASP acts together with the INO80 complex and the chaperoning activity of PARP1 to ensure efficient histone turnover and prevent the accumulation of lethal DNA damage following PARPi exposure. Collectively, our work reports on histone eviction as an immediate cellular response to PARPi treatment and provides a promising avenue for targeting histone supply pathways to overcome PARPi resistance.
2025-07-29 | GSE293482 | GEO
Project description:PARP inhibitors (PARPi) present a remarkable advance in the treatment of patients with homologous recombination (HR)-deficient tumors1-3, however resistance remains a challenge due to genomic instability4,5. While most research has focused on the downstream consequences of PARPi exposure to tackle resistance, the immediate impact of PARP inhibition on the chromatin environment and its contribution to PARPi toxicity remains elusive. Here, we show that PARP inhibition induces histone release from the chromatin. This presents a vulnerability of PARPi-resistant cancer cells, which are addicted to histone homeostasis mechanisms to sustain elevated DNA replication rates and survival. Through functional genetic screens, we identified NASP as a key factor in maintaining the stability of evicted histones via its TPR motifs. NASP loss renders tumor cells hypersensitive to PARPi treatment in vitro and in vivo, impairs replication fork progression and elevates levels of replication-associated DNA damage. Moreover, NASP acts together with the INO80 complex and the chaperoning activity of PARP1 to ensure efficient histone turnover and prevent the accumulation of lethal DNA damage following PARPi exposure. Collectively, our work reports on histone eviction as an immediate cellular response to PARPi treatment and provides a promising avenue for targeting histone supply pathways to overcome PARPi resistance.
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Project description:Breast cancer gene 2 (BRCA2) deleterious mutations confer sensitivity to poly(ADP-ribose) polymerase (PARP) inhibition due to its critical role in DNA repair. PARP inhibitor Olaparib is now approved and several other PARP inhibitors are now in different stages of clinical trials. Development of resistance to PARP inhibitors limits their clinical utility. The mechanism of resistance remains not fully understood. Here we show that amplification of mutant BRCA2 confers PARP inhibitor resistance. The amplification of mutant BRCA2 gene copies correlates with an increase in mutant BRCA2 expression and an increase in the levels of its interacting proteins PALB2 and RAD51. In addition, homologous recombination mediated DNA repair is rescued in these cells as evidenced by the formation of RAD51 focus formation. The overexpressed mutant BRCA2 is essential for the observed PARP inhibitor resistance because knockdown of its expression is sufficient to re-sensitize these cells to PARP inhibition. Collectively, our results indicate a new mechanism of resistance to PARP inhibitor in BRCA2 mutant cancer cells
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Project description:The PARP family of proteins comprises 17 members, about two thirds of which are active mono- or poly(ADP-ribosyl)transferase enzymes that transfer the ADP-ribose moiety of NAD+ onto target proteins. In many cases, ADP-ribosylation, which plays critical roles in human diseases (e.g., cancer, heart disease, and neuropathies) is associated with abrogation of the molecular functions of the target. Discerning ADP-ribosylation events mediated by a specific PARP is challenging, since all PARPs use the same substrate (i.e., NAD+) and the available inhibitors lack the specificity needed to make such conclusions. In order to identify the direct and specific targets of individual PARP family members, we have developed a chemical and genetic approach known as analog sensitivity, in which alteration of a single conserved amino acid in the active site of the PARP protein creates a pocket that allows use of an unnatural NAD+ analog containing a steric moiety. We have functionalized the steric moiety with alkyne for use in click chemistry reactions. This approach, which is transferable to other PARP family members, creates substrate specificity where none previously existed, allowing PARP-specific post-translational modification followed by target visualization, or isolation of ADP-ribosylated targets using click chemistry techniques. We have used this technology in conjunction with mass spectrometry to identify hundreds of targets both unique to, as well as shared among, the nuclear PARP proteins, PARP-1, PARP-2, and PARP-3. We have also determined the genome-wide distribution of PARP-1-specific ADP-ribosylation by coupling this analog-sensitive PARP approach with chromatin cross-linking in method that we call “Click-ChIP-seq”. We observed that PARP-1-specific ADP-ribosylation is enriched at transcriptionally active promoters in proximity to sites of PARP-1 enrichment. In addition, we observed that NELF, an important regulator of RNA Polymerase II (Pol II) pausing, is not only a target of ADP-ribosylation by PARP-1 but also spatially correlated with chromatin-associated ADP-ribose and PARP-1 in Click-ChIP-seq and ChIP-seq assays, respectively. Given these observations, we hypothesized that ADP-ribosylation might modulate NELF function and result altered Pol II pausing. We have explored this possibility using global run-on coupled with deep sequencing (GRO-seq) in MCF-7 cells in which PARP-1 was depleted by RNAi-mediated knockdown. PARP-1 depletion caused an increase in Pol II pausing genome-wide. Taken together, these results suggest the intriguing possibility that ADP-ribosylation of NELF by PARP-1 may be an important and heretofore unknown step in the release of Pol II into productive elongation.
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Project description:The PARP family of proteins comprises 17 members, about two thirds of which are active mono- or poly(ADP-ribosyl)transferase enzymes that transfer the ADP-ribose moiety of NAD+ onto target proteins. In many cases, ADP-ribosylation, which plays critical roles in human diseases (e.g., cancer, heart disease, and neuropathies) is associated with abrogation of the molecular functions of the target. Discerning ADP-ribosylation events mediated by a specific PARP is challenging, since all PARPs use the same substrate (i.e., NAD+) and the available inhibitors lack the specificity needed to make such conclusions. In order to identify the direct and specific targets of individual PARP family members, we have developed a chemical and genetic approach known as analog sensitivity, in which alteration of a single conserved amino acid in the active site of the PARP protein creates a pocket that allows use of an unnatural NAD+ analog containing a steric moiety. We have functionalized the steric moiety with alkyne for use in click chemistry reactions. This approach, which is transferable to other PARP family members, creates substrate specificity where none previously existed, allowing PARP-specific post-translational modification followed by target visualization, or isolation of ADP-ribosylated targets using click chemistry techniques. We have used this technology in conjunction with mass spectrometry to identify hundreds of targets both unique to, as well as shared among, the nuclear PARP proteins, PARP-1, PARP-2, and PARP-3. We have also determined the genome-wide distribution of PARP-1-specific ADP-ribosylation by coupling this analog-sensitive PARP approach with chromatin cross-linking in method that we call “Click-ChIP-seq”. We observed that PARP-1-specific ADP-ribosylation is enriched at transcriptionally active promoters in proximity to sites of PARP-1 enrichment. In addition, we observed that NELF, an important regulator of RNA Polymerase II (Pol II) pausing, is not only a target of ADP-ribosylation by PARP-1 but also spatially correlated with chromatin-associated ADP-ribose and PARP-1 in Click-ChIP-seq and ChIP-seq assays, respectively. Given these observations, we hypothesized that ADP-ribosylation might modulate NELF function and result altered Pol II pausing. We have explored this possibility using global run-on coupled with deep sequencing (GRO-seq) in MCF-7 cells in which PARP-1 was depleted by RNAi-mediated knockdown. PARP-1 depletion caused an increase in Pol II pausing genome-wide. Taken together, these results suggest the intriguing possibility that ADP-ribosylation of NELF by PARP-1 may be an important and heretofore unknown step in the release of Pol II into productive elongation.
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