Biology subjects

Gogola, E.

Publications and source records attributed to Gogola, E..

4 recordsLinked to original sources

bioRxiv2023

H2AX promotes replication fork degradation and chemosensitivity in BRCA-deficient tumours

Histone H2AX plays a key role in DNA damage signalling in the surrounding regions of DNA double-strand breaks (DSBs)1,2. In response to DNA damage, H2AX becomes phosphorylated on serine residue 139 (known as {gamma}H2AX), resulting in the recruitment of the DNA repair effectors 53BP1 and BRCA13-6. Here, by studying resistance to poly(ADP-ribose) polymerase (PARP) inhibitors in BRCA1/2-deficient mammary tumours7,8, we identify a novel function for {gamma}H2AX in orchestrating drug-induced replication fork degradation. Mechanistically, {gamma}H2AX-dependent replication fork degradation is elicited by the inhibition of CtIP-mediated fork protection. As a result, H2AX loss restores replication fork stability and increases chemoresistance in BRCA1/2-deficient tumour cells without restoring homology-directed DNA repair, as highlighted by the lack of DNA damage-induced RAD51 foci. Furthermore, in the attempt to discover acquired genetic vulnerabilities, we find that ATM inhibition overcomes PARP inhibitor (PARPi) resistance in H2AX-deficient tumours by interfering with CtIP-mediated fork protection of stalled forks. In summary, our results demonstrate a novel role for H2AX in replication fork biology in BRCA-deficient tumours and establish a function of H2AX separable from its classical role in DNA damage signalling and DSB repair.

cancer biology↗

bioRxiv2022

Multi-omics analysis reveals distinct non-reversion mechanisms of PARPi resistance in BRCA1- versus BRCA2-deficient mammary tumors

BRCA1 and BRCA2 both function in DNA double-strand break repair by homologous recombination (HR). Due to their HR-defect, BRCA1/2-deficient cancers are sensitive to poly(ADP-ribose) polymerase inhibitors (PARPi) but they eventually acquire resistance. Preclinical studies yielded several PARPi resistance mechanisms that do not involve BRCA1/2 reactivation, but their relevance in the clinic remains elusive. To investigate which BRCA1/2-independent mechanisms drive spontaneous resistance in vivo, we combined molecular profiling with functional analysis of the HR status of matched PARPi-naive and PARPi-resistant mouse mammary tumors harboring large intragenic deletions that prevent functional restoration of BRCA1/2. We observed restoration of HR in 64% of PARPi-resistant BRCA1-deficient tumors but none in the PARPi-resistant BRCA2-deficient tumors. Moreover, we found that 53BP1 loss is the prevalent resistance mechanism in HR-proficient BRCA1-deficient tumors, whereas resistance in BRCA2-deficient tumors is mainly induced by the loss of PARG. Our combined multi-omics analysis catalogued additional genes and pathways potentially involved in modulating PARPi response.

cancer biology↗

bioRxiv2022

MDC1 counteracts restrained replication fork restart and its loss causes chemoresistance in BRCA1/2-deficient mammary tumors

MDC1 is a key protein in DNA damage signaling. When DNA double-strand breaks (DSBs) occur, MDC1 localizes to sites of damage to promote the recruitment of other factors, including the 53BP1-mediated DSB repair pathway. By studying mechanisms of poly(ADP-ribose) polymerase inhibitor (PARPi) resistance in BRCA2;p53-deficient mouse mammary tumors, we identified a thus far unknown role of MDC1 in replication fork biology. MDC1 localizes at active replication forks during normal fork replication and its loss reduces fork speed. We show that MDC1 contributes to the restart of replication forks and thereby promotes sensitivity to PARPi and cisplatin. Loss of MDC1 causes MRE11-mediated resection, resulting in delayed fork restart. This improves DNA damage tolerance and causes chemoresistance in BRCA1/2-deficient cells. Hence, our results show a role for MDC1 in replication fork progression that mediates PARPi- and cisplatin-induced DNA damage, in addition to its role in DSB repair.

molecular biology↗

bioRxiv2021

Loss of Nuclear DNA ligase III Can Revert PARP Inhibitor Resistance in BRCA1-deficient Cells by Increasing DNA Replication Stress

Inhibitors of poly(ADP-ribose) (PAR) polymerase (PARPi) have entered the clinic for the treatment of homologous recombination (HR)-deficient cancers. Despite the success of this approach, preclinical and clinical research with PARPi has revealed multiple resistance mechanisms, highlighting the need for identification of novel functional biomarkers and combination treatment strategies. Functional genetic screens performed in cells and organoids that acquired resistance to PARPi by loss of 53BP1 identified loss of LIG3 as an enhancer of PARPi toxicity in BRCA1-deficient cells. Enhancement of PARPi toxicity by LIG3 depletion is dependent on BRCA1 deficiency but independent of the loss of 53BP1 pathway. Mechanistically, we show that LIG3 loss promotes formation of MRE11-mediated post-replicative ssDNA gaps in BRCA1-deficient and BRCA1/53BP1 double-deficient cells exposed to PARPi, leading to an accumulation of chromosomal abnormalities. LIG3 depletion also enhances efficacy of PARPi against BRCA1-deficient mammary tumors in mice, suggesting LIG3 as a potential therapeutic target.

cancer biology↗