Biology subjects

Torrecilla, I.

Publications and source records attributed to Torrecilla, I..

3 recordsLinked to original sources

bioRxiv2025

Nucleophagy removes cytotoxic trapped PARP1

Poly (ADP-Ribose) Polymerase inhibitors (PARPi) induce cytotoxicity in homologous recombination repair (HRR)-deficient cancers by causing PARP1 to become trapped on chromatin, resulting in irreparable replication-associated DNA damage. Although increased clearance of trapped PARP1 from chromatin reduces the sensitivity of cancer cells to PARPi, details surrounding this process remain unclear. PARPi exposure is known to cause increased autophagy flux, whilst autophagy inhibition can hypersensitise cells to PARPi. Using various biochemical, cell biological and live imaging-based assays, we found that trapped PARP1 is cleared by nucleophagy, the selective autophagy of nuclear substrates. Specifically, the nucleophagy of trapped PARP1 was orchestrated by the selective autophagy receptor TEX264 and its partner segregase p97/VCP. TEX264 mediates this process by directly interacting with trapped PARP1, thus bridging PARP1 to the autophagosomal resident protein LC3 for processing via autophagy. Impeding this process, either chemically or genetically, heightened PARP1 trapping, leading to accumulation of protein aggregates, replication-associated DNA damage and cell lethality, re-sensitising PARPi-resistant cells to various PARPi. In conclusion, we show that nucleophagy acts in a cytoprotective manner to directly target PARPi-induced trapped PARP1 for degradation.

cell biology↗

bioRxiv2020

SPRTN protease and SUMOylation coordinate DNA-protein crosslink repair to prevent genome instability

DNA-protein crosslinks (DPCs) are a specific type of DNA lesions where proteins are covalently attached to DNA. Unrepaired DPCs lead to genomic instability, cancer, neurodegeneration and accelerated ageing. DPC proteolysis was recently discovered as a specialised pathway for DPC repair. The DNA-dependent SPRTN protease and 26S proteasome emerged as as two independent proteolytic systems for DPC repair. DPCs are also repaired by homologous recombination (HR), a canonical DNA repair pathway. While studying the role of ubiquitin and SUMO in DPC repair, we identified mutually exclusive signalling mechanisms associated with DPC repair pathway choice. DPC modification by SUMO-1 favours SPRTN proteolysis as the preferred pathway for DPC repair. DPC SUMOylation counteracts DPC ubiquitination, which promotes DNA breaks and the switch to HR. We propose that modification of DPCs by SUMO-1 promotes SPRTN proteolysis, which is essential for DPC removal to prevent DNA replication defects, chromosomal recombination and genomic instability.

cell biology↗

bioRxiv2018

SPRTN Protease and Checkpoint Kinase 1 Cross-Activation Loop Safeguards DNA Replication

The SPRTN metalloprotease is essential for DNA-protein crosslink (DPC) repair and DNA replication in vertebrate cells. Cells deficient in SPRTN protease activity exhibit severe DPC-induced replication stress and genome instability, manifesting as premature ageing and liver cancer in humans and mice. Strikingly, SPRTN-deficient cells also show a severe G2/M checkpoint defect and fail to activate a robust checkpoint kinase 1 (CHK1) signalling cascade normally triggered in response to replication stress. Here, we show that SPRTN activates the CHK1 signalling cascade during physiological (steady-state) DNA replication by proteolysis-dependent eviction of CHK1 from chromatin. The N-terminal CHK1 fragments cleaved by SPRTN protease still possess kinase activity and phosphorylate SPRTN. This CHK1-dependent phosphorylation stimulates SPRTN recruitment to chromatin to further promote CHK1 eviction from chromatin, DPC removal and unperturbed DNA replication. Our data suggest that a SPRTN-CHK1 cross-activation loop is essential for steady-state DNA replication and protection from DNA replication stress, a major source of genome instability in diseases that cause premature ageing and cancer. In addition, we disclose a mechanism of CHK1 activation during physiological DNA replication, when long stretches of single stranded (ss) DNA that are induced by genotoxic stress and activate canonical and robust CHK1 signalling are not present.

cell biology↗