Dataset Information

Proteomic profile of BxPC3 cells after RAD51 inhibition by treatment with BRC4

ABSTRACT: RAD51 protein is an evolutionarily conserved recombinase that plays a central role in homologous recombination (HR) and DNA double strand break (DSB) repair. RAD51 inactivation by small molecules has been proposed as a strategy to impair the BRCA2/RAD51 binding and, ultimately, the HR pathway, with the aim to make cancer cells more sensitive to PARP inhibitors (PARPi). This strategy, which mimics a synthetic lethality (SL) approach, has been successfully assayed in vitro by using myr-BRC4, a peptide derived from the fourth BRC repeat of BRCA2, being the strongest reported natural RAD51 binder. The present study applies a method to obtain a proteomic fingerprint for RAD51 inhibition by the myr-BRC4 peptide (designed for a more efficient cell entry) using a mass spectroscopy (MS) proteomic approach. We performed a comparative proteomic profiling of the myr-BRC4 treated vs. untreated BxPC-3 pancreatic cancer cells and evaluated the differential expression of proteins. Among the identified proteomic hits, we focused our attention on proteins shared by both the RAD51 and the BRCA2 interactomes, and on those whose reduction showed high statistical significance. Three downregulated proteins were identified (FANCI, FANCD2, and RPA3) and protein downregulation was confirmed through immunoblotting analysis, validating the MS approach. Our results suggest that, being a direct consequence of RAD51 inhibition, the detection of FANCD2, FANCI, and RPA3 downregulation could be used as an indicator for monitoring HR impairment.

INSTRUMENT(S): timsTOF Pro

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Carcinoma Cell, Epithelial Cell

DISEASE(S): Pancreatic Carcinoma

SUBMITTER: Kieran Wynne

LAB HEAD: Giorgio Oliviero

PROVIDER: PXD042696 | Pride | 2023-08-15

REPOSITORIES: Pride

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Dataset's files

Source:

			Action	DRS
	210102kw_MarcellaProteome_35D1_Slot2-34_1_851.d.zip	Other
	210102kw_MarcellaProteome_35D1_Slot2-34_1_854.d.zip	Other
	210102kw_MarcellaProteome_35D2_Slot2-35_1_855.d.zip	Other
	210102kw_MarcellaProteome_35D2_Slot2-35_1_856.d.zip	Other
	210102kw_MarcellaProteome_35D3_Slot2-36_1_859.d.zip	Other

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Publications

Preomic profile of BxPC-3 cells after treatment with BRC4.

Previtali Viola V Myers Samuel H SH Poppi Laura L Wynne Kieran K Casamassima Irene I Girotto Stefania S Di Stefano Giuseppina G Farabegoli Fulvia F Roberti Marinella M Oliviero Giorgio G Cavalli Andrea A

Journal of proteomics 20230801

BRCA2 and RAD51 are two proteins that play a central role in homologous recombination (HR) and DNA double strand break (DSB) repair. BRCA2 assists RAD51 fibrillation and defibrillation through binding with its eight BRC repeats, with BRC4 being one of the most efficient and best characterized. RAD51 inactivation by small molecules has been proposed as a strategy to impair BRCA2/RAD51 binding and, ultimately, the HR pathway, with the aim of making cancer cells more sensitive to PARP inhibitors (P ...[more]

PMID: 37536521

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Project description:The proteins from the Fanconi Anemia (FA) pathway of DNA repair maintain DNA replication fork integrity by preventing the unscheduled degradation of nascent DNA at regions of stalled replication forks. Here, we ask if the bacterial pathogen H. pylori exploits the fork stabilisation machinery to generate double stand breaks (DSBs) and genomic instability. Specifically, we study if the H. pylori virulence factor CagA generates host genomic DSBs through replication fork destabilisation and collapse. An inducible gastric cancer model was used to examine global CagA-dependent transcriptomic and proteomic alterations, using RNA sequencing and SILAC-based mass spectrometry, respectively. The transcriptional alterations were confirmed in gastric cancer cell lines infected with H. pylori. Functional analysis was performed using chromatin fractionation, pulsed-field gel electrophoresis (PFGE), and single molecule DNA replication/repair fiber assays. We found a core set of 31 DNA repair factors including the FA genes FANCI, FANCD2, BRCA1, and BRCA2 that were downregulated following CagA expression. H. pylori infection of gastric cancer cell lines showed downregulation of the aforementioned FA genes in a CagA-dependent manner. Consistent with FA pathway downregulation, chromatin purification studies revealed impaired levels of Rad51 but higher recruitment of the nuclease MRE11 on the chromatin of CagA-expressing cells, suggesting impaired fork protection. In line with the above data, fibre assays revealed higher fork degradation, lower fork speed, daughter strands gap accumulation, and impaired re-start of replication forks in the presence of CagA, indicating compromised genome stability. By downregulating the expression of key DNA repair genes such as FANCI, FANCD2, BRCA1, and BRCA2, H. pylori CagA compromises host replication fork stability and induces DNA DSBs through fork collapse. These data unveil an intriguing example of a bacterial virulence factor that induces genomic instability by interfering with the host replication fork stabilisation machinery.