Biology subjects

Rall-Scharpf, M.

Publications and source records attributed to Rall-Scharpf, M..

3 recordsLinked to original sources

bioRxiv2026

BAP1 loss impairs Non-Homologous End Joining DNA repair promoting genomic instability

The tumor suppressor BRCA1-associated protein 1 (BAP1) is frequently mutated in uveal melanoma, where its loss is associated with poor prognosis. Although BAP1 has been implicated in homologous recombination (HR), its role in non-homologous end-joining (NHEJ) remains poorly defined. Here, we show that BAP1 functions as a central regulator of DNA double-strand break (DSB) repair by coordinating HR and NHEJ. BAP1 depletion disrupts recruitment and activity of the NHEJ machinery. Mechanistically, this defect is driven by aberrant accumulation of H2AK119-ub at DSB sites, promoting excessive DNA end resection and suppressing NHEJ activation. Importantly, inhibition of DNA end resection or suppression of H2AK119-ub restores NHEJ factor recruitment, establishing a causal link between BAP1-regulated histone modifications and repair pathway choice. Clinically, BAP1 loss correlates with genomic instability, providing a mechanistic basis for its association with poor outcomes in uveal melanoma. Collectively, these findings identify BAP1 as a gatekeeper of DSB repair fidelity, revealing a previously unrecognized role in safeguarding NHEJ and maintaining balanced DNA repair.

cancer biology↗

bioRxiv2024

BMP signaling promotes heart regeneration via alleviation of replication stress

One hallmark of aging is a decline in tissue regeneration, which can be caused by DNA replication stress. Whether highly regenerative species like zebrafish are immune from such hindrances to replication is unknown. In contrast to most mammals, adult zebrafish achieve complete heart regeneration via cell cycle entry and proliferation of mature cardiomyocytes. We found that cycling cardiomyocytes experience replication stress, which is induced by the demands of regeneration, but does not occur during physiological heart growth. Since zebrafish cardiomyocyte regeneration is remarkably efficient, heart regeneration appears to depend on elevated capabilities to overcome replication stress. Indeed, pharmacological inhibition of ATM and ATR kinases revealed that DNA damage response signaling is essential for heart regeneration. Using inducible overexpression of ligands and inhibitors of the Bone Morphogenetic Protein (BMP)-Smad pathway, combined with analysis of genetic mutants, we found that BMP signaling alleviates cardiomyocyte replication stress. In the absence of BMP signaling, cardiomyocytes become arrested in the S-phase of the cell cycle, which prevents progression to mitosis and results in heart regeneration failure. Interestingly, BMP signaling can also rescue neonatal mouse cardiomyocytes and human fibroblasts from hydroxyurea-induced replication stress. DNA fiber spreading assays in human cancer cells and human hematopoietic stem and progenitor cells (HSPCs) indicate that BMP signaling acts directly on replication dynamics by accelerating DNA replication fork progression and by facilitating their re-start after replication stress-induced stalling. Our results identify the ability to overcome replication stress as key factor for the elevated heart regeneration capacity in zebrafish. Notably, the conserved capability of BMP signaling to promote stress-free DNA replication might unlock new avenues towards anti-aging and pro-regenerative applications in humans.

developmental biology↗

bioRxiv2023

DTX3L and USP28 fine-tune DNA double strand repair through mutual regulation of their protein levels

The DNA damage response (DDR) relies on a complex protein network to maintain genomic integrity, yet the interplay between post-translational modifiers remains poorly understood. Here, we uncover a novel regulatory axis between the E3 ubiquitin ligase DTX3L and the deubiquitinase USP28 at DNA double-strand breaks (DSBs). Our results reveal a sophisticated feedback mechanism in which DTX3L ubiquitinates USP28, leading to its proteasomal degradation, while USP28 counteracts by deubiquitinating both itself and DTX3L. This cross-regulation fine-tunes DSB repair in multiple pathways, including non-homologous end joining (NHEJ), homologous recombination (HR), single-strand annealing (SSA), and microhomology-mediated end joining (MMEJ). Strikingly, the detrimental effects of USP28 depletion on these repair pathways were rescued by concurrent DTX3L knockdown. Collectively, our work uncovers a novel layer of DDR regulation in which DTX3L and USP28s antagonistic activities calibrate cellular responses to genotoxic stress, thus identifying promising therapeutic targets to combat diseases associated with genomic instability. HighlightsO_LIDTX3L and USP28 physically interact and colocalize in cellular sub-compartments, with the N-terminal D1-D3 domains of DTX3L primarily mediating the interaction C_LIO_LIDTX3L ubiquitinates USP28 for degradation, while USP28 deubiquitinates itself and DTX3L, creating a sophisticated feedback mechanism. C_LIO_LIThe DTX3L-USP28 circuit influences levels of key proteins like HIF-1, p53, and c-MYC, suggesting broader impacts on cellular stress responses. C_LIO_LIDTX3L and USP28 cooperatively regulate multiple DSB repair pathways, including NHEJ, HR, SSA, and MMEJ, with USP28 depletion effects rescued by DTX3L silencing. C_LI

biochemistry↗