Biology subjects

Gois, M. M.

Publications and source records attributed to Gois, M. M..

3 recordsLinked to original sources

bioRxiv2026

S6K1 and S6K2 regulate homologous recombination DNA repair through control of BRCA1 protein stability

Recent studies have suggested that S6 kinase 1 (S6K1) contributes to DNA repair (DR). However, the specific pathways and mechanisms involved in this regulation remain unclear. Moreover, it has not been investigated whether S6K2, a functional homologue of S6K1, also contributes to DR. In this study, we investigated the function of both S6K1 and S6K2 (S6K1/2) proteins in DR and demonstrate that both are important for efficient Homologous Recombination-mediated repair (HR). Double knockout of S6K1/2 prevented the formation of BRCA1 and RAD51 foci and increases sensitivity to DNA-damaging agents such as PARP1 inhibitors, cisplatin, and X-ray irradiation. In addition, double knockout of S6K1/2 increased markers of genomic instability, while single knockout had little effect on HR markers and genome stability, which suggests that one kinase can compensate for the loss of the other. Mechanistically, we show that S6K1/2 regulate BRCA1 protein stability, limiting its degradation by the proteasome. Finally, pharmacological inhibition of S6K1/2 sensitised HR-proficient breast cancer cells to Olaparib. Our findings clarify the role of S6K1/2 proteins in HR and suggest that targeting these kinases may be a therapeutic strategy to enhance PARP inhibitor efficacy in HR-proficient tumours.

molecular biology↗

bioRxiv2024

Finding novel vulnerabilities of hypomorphic BRCA1 alleles

With the recent rise in CRISPR/Cas9-mediated genome-wide synthetic lethality screens, many new synthetic lethal targets have been identified for diseases with underlying genetic causes such as tumours with BRCA1 mutations. Such screens often use full deficiency of a protein to identify novel vulnerabilities. However, patient-derived mutations not only result in loss of the protein but often also concern missense mutations with hypomorphic phenotypes. Here we study the genetic vulnerabilities of two previously described hypomorphic BRCA1 missense mutations and compare these to a BRCA1-depleted setting to study whether this affects screening for synthetic lethal interactions. Our research showed that BRCA1I26A mutated cells have very similar vulnerabilities to BRCA1 wildtype cells, confirming its low tumorigenic effect. In contrast, the BRCA1R1699Q mutation induced a more similar phenotype to BRCA1-deficient cells. For this mutation, we also unveiled a unique vulnerability to the loss of NDE1. Specifically in BRCA1R1699Q mutated cells, and not BRCA1-proficient or -deficient cells, NDE1 loss leads to increased genomic instability. Altogether our findings highlight the importance to differentiate between patient-derived mutations when assessing novel treatment targets.

cancer biology↗

bioRxiv2021

Characterization of the interaction between SARS-CoV-2 Membrane Protein and Proliferating Cell Nuclear Antigen (PCNA) as a Potential Therapeutic Target

SARS-CoV-2 is an emerging virus from the Coronaviridae family and is responsible for the ongoing COVID-19 pandemic. In this work, we explored the previously reported SARS-CoV-2 structural membrane protein (M) interaction with human Proliferating Cell Nuclear Antigen (PCNA). The M protein is responsible for maintaining virion shape, and PCNA is a marker of DNA damage which is essential for DNA replication and repair. We validated the M PCNA interaction through immunoprecipitation, immunofluorescence co-localization, and a PLA assay. In cells infected with SARS-CoV-2 or transfected with M protein, using immunofluorescence and cell fractioning, we documented a reallocation of PCNA from the nucleus to the cytoplasm and the increase of PCNA and {gamma}H2AX (another DNA damage marker) expression. We also observed an increase of PCNA and {gamma}H2AX expression in the lung of a COVID-19 patient by immunohistochemistry. In addition, the inhibition of PCNA translocation by PCNA I1 and Verdinexor led to a reduction of plaque formation in an in vitro assay. We, therefore, propose that the transport of PCNA to the cytoplasm and its association with M could be a virus strategy to manipulate cell functions and may be considered a target for COVID-19 therapy.

molecular biology↗